Effectiveness of substance use disorder treatment as an alternative to imprisonment

INTRODUCTION

Drug courts are criminal justice programs to divert people with substance use disorders from incarceration into treatment. Drug courts have become increasingly popular in the US and other countries. However, their effectiveness in reducing important public health outcomes such as recidivism and substance-related health harms remains ambiguous and contested. We used nationwide register data from Sweden to evaluate the effectiveness of contract treatment sanction, the Swedish version of drug court, in reducing substance misuse, adverse somatic and mental health outcomes, and recidivism.

METHODS

In this prospective cohort study, two quasi-experimental designs were used: difference-in-differences and the within-individual design. In the latter, we compared the risk of outcomes during time on contract treatment to, 1) parole after imprisonment and, 2) probation.

RESULTS

The cohort included 11,893 individuals (13% women) who underwent contract treatment. Contract treatment was associated with a reduction of 7 percentage points (95% CI: -.088, -.055) in substance misuse, 5 percentage points (-.064, -.034) in adverse mental health events, 9 percentage points (-.113, -.076) in adverse somatic health events, and 3 fewer charges (-3.16, -2.85) for crime in difference-in-differences analyses. Within-individual associations suggested that the same individual had longer times-to-event for all outcomes during contract treatment than on parole or on probation.

CONCLUSIONS

Contract treatment is an effective intervention from both public health and criminal justice perspective. Our findings suggest that it is a superior alternative to incarceration in its target group. Further, we find that an implementation approach that is less punitive and more inclusive than what is typical in the US can be successful.

Patterns and predictors of alcohol misuse trajectories from adolescence through early midlife

We took a multilevel developmental contextual approach and characterized trajectories of alcohol misuse from adolescence through early midlife, examined genetic and environmental contributions to individual differences in those trajectories, and identified adolescent and young adult factors associated with change in alcohol misuse. Data were from two longitudinal population-based studies. FinnTwin16 is a study of Finnish twins assessed at 16, 17, 18, 25, and 35 years (N = 5659; 52% female; 32% monozygotic). The National Longitudinal Study of Adolescent to Adult Health (Add Health) is a study of adolescents from the United States, who were assessed at five time points from 1994 to 2018 (N = 18026; 50% female; 64% White, 21% Black, 4% Native American, 7% Asian, 9% Other race/ethnicity). Alcohol misuse was measured as frequency of intoxication in FinnTwin16 and frequency of binge drinking in Add Health. In both samples, trajectories of alcohol misuse were best described by a quadratic growth curve: Alcohol misuse increased across adolescence, peaked in young adulthood, and declined into early midlife. Individual differences in these trajectories were primarily explained by environmental factors. Several adolescent and young adult correlates were related to the course of alcohol misuse, including other substance use, physical and mental health, and parenthood.

Associations between sleep medication use and alcohol consumption over 36 years in Finnish twins

BACKGROUND

Sleep medication use is an indicator of underlying sleep problems that might be induced by various factors such as alcohol use. However, the longitudinal relationship between drinking and sleep problems remains poorly understood. We investigated associations between sleep medication and alcohol use throughout adulthood, and examined the role of familial and potential confounding factors contributing to these associations.

METHODS

We used information of zygosity and self-report questionnaire data over a follow-up period of 36 years from the Older Finnish Twin Cohort (N=13,851).

RESULTS

Logistic regression analyses suggested consistent associations between sleep medication use and heavy/binge drinking at all four time points (OR range =1.36-3.18, P <0.05), implying that increased drinking is associated with increased sleep medication use over time. Cross-lagged path analyses suggested that moderate/heavy and binge drinking predict sleep medication use at most time points (OR range = 1.15-1.94, P <0.05), whilst sleep medication use predicts subsequent abstaining from alcohol (OR range =2.26-2.47, P <0.05). Within-pair analyses implied that familial factors play a role, and quantitative genetic modelling estimated genetic factors to explain approximately 80% of the lifetime association of sleep medication use with moderate/heavy and binge drinking.

CONCLUSIONS

Drinking is associated with sleep medication use throughout adulthood. Further, our results suggest that drinking is likely to predict sleep medication use, thereby potentially constituting a risk factor for sleep problems, and that genetic factors contribute to the association. These findings are important in terms of better understanding the development of sleep and alcohol use disorders.

Parental substance use disorder and risk of intellectual disability in offspring in Sweden: a national register study

Background

Intellectual disability (ID) is a disorder with unknown aetiology in many cases. Maternal alcohol use is a known risk factor for ID, but less is known about the importance of maternal and paternal substance use disorder (SUD) and risk of ID in offspring.

Methods

Data from multiple nationwide registers were used to create a cohort of children born from January 01, 1978 to December 31, 2002. All participants were born in Sweden, had available parental identification information and did not emigrate or die before age 12 (n = 1,940,820). Logistic regression modelling was performed with exposure defined as having a parent who received any SUD diagnosis, including alcohol use disorder (AUD) and drug use disorder (DUD). The outcome was registration of diagnosis of any form of ID. First, we analysed the risk of ID if parental SUD was registered prior to childbirth with stepwise adjustment of multiple covariates. Second, the effect of timing of SUD diagnosis in relation to childbirth was analysed.

Findings

Of 37,410 offspring with parental SUD registered prior to birth, 3.0% (n = 1110) had any form of ID compared to 1.2% (n = 23,168) of those 1,903,410 individuals without parental SUD prior birth. Parental SUD prior birth was associated with an increased risk of any form of ID (Odds Ratio [OR]: 2.3 [2.2-2.5]), with ORs similar for maternal (OR: 2.3 [2.1-2.5]) and paternal SUD (OR: 2.3 [2.1-2.5]). These ORs were reduced but remained statistically significant after adjusting for parental education, migration, psychiatric comorbidity, and co-parent SUD (OR parental SUD: 1.6 [1.5-1.8]; OR maternal SUD: 1.4 [1.2-1.5]; OR paternal SUD: 1.6 [1.5-1.7]). Parental SUD was associated with increased risk of ID in offspring irrespective of timing of diagnosis, but if mothers or fathers were diagnosed with AUD during pregnancy (OR maternal AUD: 5.0 [3.1-8.2]; OR paternal AUD: 2.8 [2.2-3.6]), the risk was significantly greater than if the AUD diagnosis was first registered after childbirth (OR maternal AUD: 1.9 [1.8-2.0]; OR paternal AUD: 1.6 [1.6-1.7]).

Interpretation

Both paternal and maternal SUD were associated with an increased risk of ID in offspring, with greatest risk observed when AUD was diagnosed during pregnancy. Possible mechanisms may involve shared genetic and environmental factors, including toxic effects from alcohol intake. These findings have clinical implications in suggesting that parental SUD in either parent represents a possibly modifiable risk factor to consider when developing prevention, diagnostics and treatment programs for children with ID.

Funding

Stockholm County Council, the Research Council of the Swedish Alcohol Retailing Monopoly, Fredrik and Ingrid Thurings stiftelse, Academy of Finland, the Swedish Research Council and the Swedish Research Council for Health, Working Life and Welfare, Nordforsk by the Nordic Council of Ministers and the Polish Medical Research Agency.

Hormonal contraception use and insomnia: A nested case-control study

Evidence is limited concerning possible associations between the use of hormonal contraception and insomnia. We applied the nested case-control design on a nationwide sample of women, aged 15-49 years, derived from national health care registries to characterize the association between the use of hormonal contraception and the occurrence of insomnia. There were altogether 294,356 users and 294,356 non-users of hormonal contraception. 11,105 new cases of insomnia emerged among the 1,148,969 person-years of the follow-up period of two years. All the significant associations of hormonal contraception with insomnia emerged among the participants aged 34 years or younger, and if only the tertiary care data was concerned, among the those aged 15-19 years. The users of the fixed combination of drospirenone and ethinylestradiol as well as that of cyproterone and ethinylestradiol had significantly decreased odds for insomnia, whereas the users levonorgestrel-releasing intrauterine devise as well as those of vaginal ring with etonogestrel and ethinylestradiol had significantly increased odds for insomnia as compared with non-users. Our findings suggest that different products prescribed for hormonal contraception may be differentially associated with the occurrence of insomnia.

Association of intellectual disability with violent and sexual crime and victimization: a population-based cohort study

BACKGROUND

Intellectual disability (ID) is associated with violent and sexual offending and victimization, but the importance of neuropsychiatric comorbidity and severity of disability remains unclear.

METHODS

In a register-based cohort study of people born in Sweden 1980-1991 (n = 1 232 564), we investigated associations of mild and moderate/severe ID with any, violent and sexual crimes, and with assault victimization, stratified by comorbid autism and attention deficit hyperactivity disorder (ADHD). We defined ID by attendance at a special school or registered diagnosis and obtained data on criminal convictions and injuries or deaths due to assaults from nationwide registers until end of 2013.

RESULTS

Compared to people without ID, autism or ADHD, men and women with mild or moderate/severe ID and comorbid ADHD had elevated risks of violent crimes [range of hazard ratios (HRs) 4.4-10.4] and assault victimization (HRs 2.0-7.7). Women with mild ID without comorbidities or with comorbid autism also had elevated risks of violent crimes and victimization (HRs 1.8-4.6) compared to women without ID, autism or ADHD. The relative risks of sexual offending and victimization were elevated in men and women with ID without comorbidities (HRs 2.6-12.7). The highest risks for sexual offending in men (HRs 9.4-11.0) and for sexual assault victimization in women (HRs 11.0-17.1) related to ID and comorbid ADHD.

CONCLUSIONS

The elevated risk of violent offending and assault victimization in people with ID is largely explained by comorbid ADHD, whereas ID is independently associated with sexual crimes and victimization, even though absolute risks are low.

General and violent recidivism of former forensic psychiatric patients in Finland

Background

Forensic psychiatric care in Finland is provided to individuals who have committed a crime due to a serious mental disorder and are in need of psychiatric care. The reconviction (recidivism) rates for this patient group vary in time and between countries, likely due to different treatment practices and requirements for forensic care.

Materials and methods

We set out to study criminal recidivism in a national cohort of all patients released from forensic psychiatric care in Finland between 1999 and 2018. National registries were used to identify the patients and gain information on their criminal sentences. Forensic psychiatric examinations were used to record demographic information for the cohort. The cohort was followed up from hospital discharge to the end of 2019.

Results

We identified a total of 501 patients who were released from forensic psychiatric care (mean age: 46.6 years [SD 13.4), 434 (86.6%) were male). The mean and median times spent in treatment for the cohort was 10.0 years [SD 6.5] and 8.7 years, respectively. 91% of the patients had schizophrenia spectrum disorder (F2*), and 63.5% had a substance use disorder. A total of 83 patients (16.6%) committed any crime after being released from care, and the mean time to recidivism was 3.8 years. The recidivism rate was 2015 per 100,000 person years. A total of 48 patients (9.6%) committed a violent crime. The mean time to violent recidivism was 4.2 years. The violent recidivism rate was 1,083 per 100,000 person years. A longer duration of treatment was associated with a decreased risk of general recidivism (HR 0.95, 95% CI 0.90 to 1.00, p = 0.05). Factors associated with higher recidivism were male sex, having a comorbid substance use disorder and younger age at discharge.

Conclusion

The recidivism rate in Finland was markedly lower than has been previously reported for other Western countries, and the mean duration of treatment was also longer. A longer treatment time may reduce the risk of criminal recidivism in forensic psychiatric patients. The results suggest, as previous studies have found, that more effort is indicated on the treatment of substance abuse.

Genetic and Environmental Factors Underlying Parallel Changes in Body Mass Index and Alcohol Consumption: A 36-Year Longitudinal Study of Adult Twins

INTRODUCTION

While the genetic and environmental underpinnings of body weight and alcohol use are fairly well-known, determinants of simultaneous changes in these traits are still poorly known. We sought to quantify the environmental and genetic components underlying parallel changes in weight and alcohol consumption and to investigate potential covariation between them.

METHODS

The analysis comprised 4,461 adult participants (58% women) from the Finnish Twin Cohort with four measures of alcohol consumption and body mass index (BMI) over a 36-year follow-up. Trajectories of each trait were described by growth factors, defined as intercepts (i.e., baseline) and slopes (i.e., change over follow-up), using latent growth curve modeling. Growth values were used for male (190 monozygotic pairs, 293 dizygotic pairs) and female (316 monozygotic pairs, 487 dizygotic pairs) same-sex complete twin pairs in multivariate twin modeling. The variances and covariances of growth factors were then decomposed into genetic and environmental components.

RESULTS

The baseline heritabilities were similar in men (BMI: h2 = 79% [95% confidence interval: 74, 83]; alcohol consumption: h2 = 49% [32, 67]) and women (h2 = 77% [73, 81]; h2 = 45% [29, 61]). Heritabilities of BMI change were similar in men (h2 = 52% [42, 61]) and women (h2 = 57% [50, 63]), but the heritability of change in alcohol consumption was significantly higher (p = 0.03) in men (h2 = 45% [34, 54]) than in women (h2 = 31% [22, 38]). Significant additive genetic correlations between BMI at baseline and change in alcohol consumption were observed in both men (rA = -0.17 [-0.29, -0.04]) and women (rA = -0.18 [-0.31, -0.06]). Non-shared environmental factors affecting changes in alcohol consumption and BMI were correlated in men (rE = 0.18 [0.06, 0.30]). Among women, non-shared environmental factors affecting baseline alcohol consumption and the change in BMI were inversely correlated (rE = -0.11 [-0.20, -0.01]).

CONCLUSIONS

Based on genetic correlations, genetic variation underlying BMI may affect changes in alcohol consumption. Independent of genetic effects, change in BMI correlates with change in alcohol consumption in men, suggesting direct effects between them.

Clinical, environmental, and genetic risk factors for substance use disorders: characterizing combined effects across multiple cohorts

Substance use disorders (SUDs) incur serious social and personal costs. The risk for SUDs is complex, with risk factors ranging from social conditions to individual genetic variation. We examined whether models that include a clinical/environmental risk index (CERI) and polygenic scores (PGS) are able to identify individuals at increased risk of SUD in young adulthood across four longitudinal cohorts for a combined sample of N = 15,134. Our analyses included participants of European (NEUR = 12,659) and African (NAFR = 2475) ancestries. SUD outcomes included: (1) alcohol dependence, (2) nicotine dependence; (3) drug dependence, and (4) any substance dependence. In the models containing the PGS and CERI, the CERI was associated with all three outcomes (ORs = 01.37-1.67). PGS for problematic alcohol use, externalizing, and smoking quantity were associated with alcohol dependence, drug dependence, and nicotine dependence, respectively (OR = 1.11-1.33). PGS for problematic alcohol use and externalizing were also associated with any substance dependence (ORs = 1.09-1.18). The full model explained 6-13% of the variance in SUDs. Those in the top 10% of CERI and PGS had relative risk ratios of 3.86-8.04 for each SUD relative to the bottom 90%. Overall, the combined measures of clinical, environmental, and genetic risk demonstrated modest ability to distinguish between affected and unaffected individuals in young adulthood. PGS were significant but added little in addition to the clinical/environmental risk index. Results from our analysis demonstrate there is still considerable work to be done before tools such as these are ready for clinical applications.

Parental alcohol and drug abuse and offspring mortality by age 10: a population-based register study

BACKGROUND

Parental substance abuse (SA) of alcohol and drugs is associated with offspring mortality, including sudden infant death syndrome (SIDS), in infancy, but research on cause-specific mortality and mortality in later childhood is scarce.

METHODS

Using population-based register data on all births in Sweden in 1973-2013 (N = 4.2 million) and Cox regressions, we examined the associations of mother's and father's SA registered between 2 years before and 12 years after the child birth with offspring all-cause and cause-specific mortality in infancy and childhood.

RESULTS

Parental SA was associated with increased offspring all-cause and natural-cause mortality in infancy, but not in the neonatal period, and with external-cause mortality in ages 1-9. Risk of SIDS was 130-280% higher in infants with parental SA compared to infants with no parental SA. Adjusting for parental socioeconomic and immigrant status and severe psychiatric disorders, paternal SA was associated with 66% higher mortality due to communicable diseases and infections in infancy, and both maternal and paternal SA were associated with 40-174% higher mortality due to accidents in infancy and in ages 1-9. The associations between parental SA and offspring mortality were similar for male and female offspring.

CONCLUSIONS

Child mortality is rare in contemporary Sweden, and parental SA has variable associations with elevated offspring mortality throughout the first 10 years of life, excluding the neonatal period, which is indicative of insufficient recognition of children at risk. Preventive measures should be long-term and targeted to both parental and offspring behaviour.

Literacy skills seem to fuel literacy enjoyment, rather than vice versa

Children who like to read and write tend to be better at it. This association is typically interpreted as enjoyment impacting engagement in literacy activities, which boosts literacy skills. We fitted direction-of-causation models to partial data of 3690 Finnish twins aged 12. Literacy skills were rated by the twins' teachers and literacy enjoyment by the twins themselves. A bivariate twin model showed substantial genetic influences on literacy skills (70%) and literacy enjoyment (35%). In both skills and enjoyment, shared-environmental influences explained about 20% in each. The best-fitting direction-of-causation model showed that skills impacted enjoyment, while the influence in the other direction was zero. The genetic influences on skills influenced enjoyment, likely via the skills→enjoyment path. This indicates an active gene-environment correlation: children with an aptitude for good literacy skills are more likely to enjoy reading and seek out literacy activities. To a lesser extent, it was also the shared-environmental influences on children's skills that propagated to influence children's literacy enjoyment. Environmental influences that foster children's literacy skills (e.g., families and schools), also foster children's love for reading and writing. These findings underline the importance of nurturing children's literacy skills. HIGHLIGHTS: It's known that how much children enjoy reading and writing and how good they are at it correlates ∼0.30, but causality remains unknown. We tested the direction of causation in 3690 twins aged 12. Literacy skills impacted literacy enjoyment, but not the other way around. Genetics influence children's literacy skills and how much they like and choose to read and write, indicating genetic niche picking.

Exploring the relationships between adolescent alcohol misuse and later life health outcomes

BACKGROUND

We sought to clarify the impact of adolescent alcohol misuse on adult physical health and subjective well-being. To do so, we investigated both the direct associations between adolescent alcohol misuse and early midlife physical health and life satisfaction and the indirect effects on these outcomes attributable to subsequent alcohol problems.

METHOD

The sample included 2733 twin pairs (32% monozygotic; 52% female) from the FinnTwin16 study. Adolescent alcohol misuse was a composite of frequency of drunkenness, frequency of alcohol use, and alcohol problems at ages 16, 17, and 18.5. The early midlife outcomes included somatic symptoms, self-rated health, and life satisfaction at age 34. The mediators examined as part of the indirect effect analyses included alcohol problems from the Rutgers Alcohol Problem Index at ages 24 and 34. Serial mediation and co-twin comparison models were applied and included covariates from adolescence and early midlife.

RESULTS

There were weak direct associations between adolescent alcohol misuse and early midlife physical health and life satisfaction. However, there was stronger evidence for indirect effects, whereby young adult and early midlife alcohol problems serially mediated the relationship between adolescent alcohol misuse and early midlife somatic symptoms (β = 0.03, 95% CI [0.03, 0.04]), self-rated health (β = -0.02, 95% CI [-0.03, -0.01]), and life satisfaction (β = -0.03, CI [-0.04, -0.02]). These serial mediation effects were robust in co-twin comparison analyses.

CONCLUSIONS

These results provide evidence that alcohol problems are a primary driver linking adolescent alcohol misuse and poor health outcomes across the lifespan.

Alcohol consumption at age 18-25 and number of children at a 33-year follow-up: Individual and within-pair analyses of Finnish twins

BACKGROUND

Do drinking patterns in late adolescence/early adulthood predict lifetime childlessness and number of children? Research on this question has been only tangentially relevant and the results inconsistent. The designs used to date have been compromised by genetic and environmental confounds that are poorly controlled; covariate effects of smoking and education that are often ignored; males being understudied; population-based sampling rare, and long-term prospective studies with genetically informative designs yet to be reported.

METHOD

In a 33-year follow-up, we linked the drinking patterns of >3500 Finnish twin pairs, assessed at ages 18-25, to registry data on their eventual number of children. Analyses distinguished associations of early drinking patterns with lifetime childlessness from those predictive of family size. Within-twin pair analyses used fixed-effects regression models to account for shared familial confounds and genetic liabilities. Childlessness was analyzed with Cox proportional hazards models and family size with Poisson regression. Analyses within-pairs and of twins as individuals were run before and after adjustment for smoking and education, and for oral contraceptive (OC) use in individual-level analyses of female twins.

RESULTS

Baseline abstinence and heavier drinking both significantly predicted lifetime childlessness in individual-level analyses. Few abstinent women used OCs, but they were nonetheless more often eventually childless; adjusting for smoking and education did not affect this finding. Excluding childless twins, Poisson models of family size showed heavier drinking at 18-25 to be predictive of fewer children in both men and women. Those associations were replicated in within-pair analyses of dizygotic twins, each level of heavier drinking being associated with smaller families. Among monozygotic twins, associations of drinking with completed family size yielded effects of similar magnitude, reaching significance at the highest levels of consumption, ruling out familial confounds.

CONCLUSIONS

Compared to moderate levels of drinking, both abstinence and heavier drinking in late adolescence/early adulthood predicted a greater likelihood of lifetime childlessness and eventual number of children. Familial confounds do not fully explain these associations.

Alcohol use and poor sleep quality: a longitudinal twin study across 36 years

Study Objectives

Poor sleep is one of the multiple health issues associated with heavy alcohol consumption. While acute effects of alcohol intake on sleep have been widely investigated, the longitudinal associations remain relatively underexplored. The objective of our research was to shed light on cross-sectional and longitudinal associations between alcohol use and poor sleep quality over time, and to elucidate the role of familial confounding factors in such associations.

Methods

Using self-report questionnaire data from the Older Finnish Twin Cohort (N = 13 851), we examined how alcohol consumption and binge drinking are associated with sleep quality during a period of 36 years.

Results

Cross-sectional logistic regression analyses revealed significant associations between poor sleep and alcohol misuse, including heavy and binge drinking, at all four time points (OR range = 1.61-3.37, p < .05), suggesting that higher alcohol intake is associated with poor sleep quality over the years. Longitudinal cross-lagged analyses indicated that moderate, heavy and binge drinking predict poor sleep quality (OR range = 1.25-1.76, p < .05), but not the reverse. Within-pair analyses suggested that the associations between heavy drinking and poor sleep quality were not fully explained by genetic and environmental influences shared by the co-twins.

Conclusions

In conclusion, our findings support previous literature in that alcohol use is associated with poor sleep quality, such that alcohol use predicts poor sleep quality later in life, but not vice versa, and that the association is not fully explained by familial factors.

Metabolomics profile of 5649 users and non-users of hormonal intrauterine devices in Finland

BACKGROUND

Use of hormonal intrauterine devices has grown during the last decades. Although the hormonal intrauterine devices act mostly via local effects on uterus, measurable concentrations of levonorgestrel are absorbed into the systemic circulation. The possible metabolic changes and large scale biomarker profiles associated with the hormonal intrauterine devices have not yet been studied in detail.

OBJECTIVES

To examine, through the metabolomics approach, the metabolic profile of the hormonal intrauterine device use, its associations as a function of the duration of use, as well as those with after discontinuation of the hormonal intrauterine device use.

STUDY DESIGN

The study consists of cross-sectional analyses of five population-based surveys (FINRISK and FinHealth studies), spanning 1997-2017. All fertile aged (18-49 years) participants in the surveys with available information on hormonal contraceptive use and metabolomics data (n=5649), were included in the study. Altogether 211 metabolic measures in users of hormonal intrauterine devices (n=1006) were compared to those in non-users of hormonal contraception (n=4643) via multivariable linear regression models. In order to allow the comparison across multiple measures, association magnitudes are reported in SD units of difference in biomarker concentration compared to the reference group.

RESULTS

After adjustment for covariates, levels of 141 metabolites differed in current users of hormonal intrauterine devices compared to non-users of hormonal contraception (median difference in biomarker concentration: 0.09 SD): lower levels of particle concentration of larger lipoprotein subclasses, triglycerides, cholesterol and derivatives, apolipoproteins A and B, fatty acids, glycoprotein acetyls and aromatic amino acids. The metabolic pattern of the hormonal intrauterine device use did not change according to the duration of use. When comparing previous users and never-users of hormonal intrauterine devices, no significant metabolic differences emerged.

CONCLUSIONS

The use of hormonal intrauterine devices was associated with several moderate metabolic changes, previously associated with reduced arterial cardiometabolic risk. The metabolic effects were independent of the duration of use of the hormonal intrauterine devices. Moreover, the metabolic profiles were similar after discontinuation of the hormonal intrauterine devices and in never-users.

Association of Obsessive-Compulsive Disorder and Obsessive-Compulsive Symptoms With Substance Misuse in 2 Longitudinal Cohorts in Sweden

IMPORTANCE

Neurobiological models have postulated shared neural mechanisms between obsessive-compulsive disorder (OCD) and substance use disorders, but results from clinical and epidemiological studies are conflicting or even suggest that OCD may be protective against substance misuse.

OBJECTIVE

To investigate whether OCD and obsessive-compulsive symptoms are associated with substance misuse and the extent to which shared genetic and/or environmental factors account for this association.

DESIGN, SETTING, AND PARTICIPANTS

In this cohort study, individuals in the general population of Sweden born between January 1, 1932, and December 31, 1997 (population cohort), were followed up through Swedish nationwide registers from January 1, 1997, to December 31, 2013. The second cohort included twin participants in the Child and Adolescent Twin Study in Sweden (CATSS) followed up from ages 18 to 24 years. Data were analyzed from March 1, 2021, to March 31, 2022.

EXPOSURES

Lifetime International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, diagnosis of OCD in the National Patient Register (population cohort 1), and self-reported obsessive-compulsive symptoms at 18 years of age (CATSS cohort).

MAIN OUTCOMES AND MEASURES

Substance misuse was defined as registered substance use-related disorder, criminal conviction, or death (population cohort), and self-reported alcohol and drug dependence symptoms at 18 and 24 years of age (CATSS cohort).

RESULTS

The general population cohort included 6 304 188 individuals (48.9% women and 51.1% men; median baseline age, 30.5 [IQR, 15.0-46.4] years), of whom 27 342 had an OCD diagnosis. Obsessive-compulsive disorder was associated with an elevated risk of substance misuse (hazard ratio, 3.68 [95% CI, 3.52-3.85]). In the 9230 individuals in the CATSS cohort (5551 women [60.1%] and 3679 men [39.9%]), obsessive-compulsive symptoms at 18 years of age were associated with increased symptoms of alcohol dependence (concurrent [n = 9219], β = 0.18 [95% CI, 0.16-0.20]; longitudinal [n = 3381], β = 0.10 [95% CI, 0.06-0.14]) and drug dependence (concurrent [n = 749], β = 0.19 [95% CI, 0.11-0.27]; longitudinal [n = 452], β = 0.15 [95% CI, 0.04-0.25]). Comorbid anxiety and depression did not entirely explain the associations in either cohort. Using data from full siblings and maternal half-siblings (population cohort) and monozygotic and dizygotic twins (CATSS cohort) provided estimates of the relative contribution of genetic and environmental influences to the covariance between OCD and obsessive-compulsive symptoms and substance misuse or dependence. The associations were explained by genetic (56%-68%) and nonshared environmental (32%-44%) factors.

CONCLUSIONS AND RELEVANCE

The findings of this Swedish population-based cohort study challenge the notion that OCD is protective against developing substance misuse. The association of OCD and obsessive-compulsive symptoms with substance misuse was largely explained by shared genetics but was also compatible with partial environmental mediation.

Use of hormonal contraception and attempted suicide: a nested case-control study

Introduction

In Finland more than 40% of fertile aged women used some type of hormonal contraception (HC) in the period 2010-2013. A proportion of women using HC complains of side effects, including mood symptoms. The relationship between the use of HC and the risk of attempted suicide (AS) is still a matter of debate.

Objectives

To assess the association of the use of HC with the risk of AS during 2017-2019.

Methods

Data were retrieved from the Prescription Centre, Care Register of Health Care, Register of Primary Health Care Visits and Statistics Finland. A total of 587 823 women, aged 15-49 years, using and not using HC in 2017 were analysed in the initial incidence study. All incident AS cases during 2018-2019, and their 4:1 age-matched controls (1 174 346 person-years) were analysed in a nested case-control setting via conditional logistic regression models.

Results

Altogether 818 AS cases occurred during the follow-up (incidence rate: 0.70/1000 person-years, 95% CI 0.65–0.75), with an IRR of HC vs. no-HC use of 0.73 (0.63–0.83). Current use (in the 180 days before the event) of estradiol- or ethinylestradiol-containing HC was associated with a lower risk of AS (0.53, 0.33–0.87; 0.49, 0.37–0.64, respectively) compared to non-use of HC. After controlling for covariates (marital and socioeconomic status, education level, use of psychotropic medications), only current use of HC containing ethinylestradiol remained significant (0.39, 0.23–0.65).

Conclusions

A lower risk of AS is associated with the use of HC, and specifically of ethinylestradiol-containing HC.

Disclosure

No significant relationships.

Systemic hormonal contraception and risk of venous thromboembolism

INTRODUCTION

The increased risk of venous thromboembolism associated with the use of hormonal contraception is well recognized, but evidence regarding hormonal contraception containing natural estradiol is limited. This study aimed to assess the associations between the patterns of use of different systemic hormonal contraceptives and the risk of venous thromboembolism during 2017-2019.

MATERIAL AND METHODS

All fertile-aged women (15-49 years) living in Finland in 2017 and using hormonal contraception in 2017 and their 1:1 age- and residence-matched controls not using hormonal contraception in 2017 (altogether 587 559 women) were selected from the Prescription Centre. All incident venous thromboembolism cases during 2018-2019 and their 4:1 age-matched controls were further analyzed in a prospective nested case-control design to assess the associations between the use (starting, stopping, continuous vs no use) of different hormonal contraception types and venous thromboembolism.

RESULTS

Altogether, 1334 venous thromboembolism cases occurred during the follow-up period (incidence rate 1.14 per 1000 person-years, 95% confidence interval [CI] 1.08-1.20), with an incidence rate ratio of hormonal contraception vs no hormonal contraception use of 1.42 (95% CI 1.27-1.58). Compared with non-use, starting the use of gestodene and ethinylestradiol (adjusted odds ratio [aOR] 2.85; 95% CI 1.62-5.03), drospirenone and ethinylestradiol (aOR 1.55; 95% CI 0.98-2.44), desogestrel and ethinylestradiol (aOR 1.97; 95% CI 0.99-3.92), and transdermal patch releasing norelgestromin and ethinylestradiol (aOR 5.10; 95% CI 1.12-23.16), as well as continuing the use of gestodene and ethinylestradiol (aOR 2.60; 95% CI 1.61-4.21), drospirenone and ethinylestradiol (aOR 1.55; 95% CI 1.02-2.37), cyproterone-acetate and estrogen/ethinylestradiol (aOR 1.66; 95% CI 1.06-2.61), and vaginal ring releasing etonogestrel and ethinylestradiol (aOR 3.27; 95% CI 1.95-5.48) were associated with venous thromboembolism risk. Regarding the type of estrogen, the highest risk was associated with current use (vs non use in the previous 180 days) of ethinylestradiol-containing preparations (aOR 2.20; 95% CI 1.82-2.65), followed by estradiol-containing preparations (aOR 1.39; 95% CI 1.04-1.87) with no risk for progestin-only hormonal contraception. Current use of estradiol-containing preparations was not associated with venous thromboembolism risk after exclusion of cyproterone-acetate and estrogen/ethinylestradiol (aOR 1.05; 95% CI 0.66-1.66).

CONCLUSIONS

An increased risk of venous thromboembolism is associated with ethinylestradiol-containing combined preparations. The use of estradiol-containing combined preparations confers only a slightly increased risk, possibly driven by cyproterone-containing combined oral contraceptives, whereas the use of progestin-only contraception is not associated with venous thromboembolism.

Within-sibship genome-wide association analyses decrease bias in estimates of direct genetic effects

Estimates from genome-wide association studies (GWAS) of unrelated individuals capture effects of inherited variation (direct effects), demography (population stratification, assortative mating) and relatives (indirect genetic effects). Family-based GWAS designs can control for demographic and indirect genetic effects, but large-scale family datasets have been lacking. We combined data from 178,086 siblings from 19 cohorts to generate population (between-family) and within-sibship (within-family) GWAS estimates for 25 phenotypes. Within-sibship GWAS estimates were smaller than population estimates for height, educational attainment, age at first birth, number of children, cognitive ability, depressive symptoms and smoking. Some differences were observed in downstream SNP heritability, genetic correlations and Mendelian randomization analyses. For example, the within-sibship genetic correlation between educational attainment and body mass index attenuated towards zero. In contrast, analyses of most molecular phenotypes (for example, low-density lipoprotein-cholesterol) were generally consistent. We also found within-sibship evidence of polygenic adaptation on taller height. Here, we illustrate the importance of family-based GWAS data for phenotypes influenced by demographic and indirect genetic effects.

Association of Tourette Syndrome and Chronic Tic Disorder With Violent Assault and Criminal Convictions

Importance

Tic disorders are associated with multiple social adversities, but little is known about the experience of violent assault (including sexual assault) and criminality in this group.

Objective

To establish if Tourette syndrome (TS) and chronic tic disorder (CTD) are associated with an increased risk of experiencing violent assault and criminal convictions.

Design, Setting, and Participants

In this cohort study, all individuals living in Sweden at any time between January 1, 1973, and December 31, 2013, were identified from Swedish nationwide health and administrative registers. Cox proportional hazards regression models were used to estimate the risk of violent assault and criminal convictions among people with TS or CTD, compared with the general population and unaffected full siblings. Data analyses were conducted between September 1 and October 22, 2021.

Exposures

The Swedish version of the International Classification of Diseases, Eighth Revision (ICD-8), ICD-9, and ICD-10 diagnoses of TS or CTD in the Swedish National Patient Register.

Main Outcomes and Measures

Records of sexual and nonsexual violent assault and death due to violent assaults were obtained from the National Patient Register and the Cause of Death Register, respectively. Convictions for violent and nonviolent criminal offenses were obtained from the Crime Register. Covariates included sex and birth year.

Results

The study cohort included 13 819 284 individuals living in Sweden between 1973 and 2013. A total of 7791 individuals with TS or CTD were identified (median [IQR] age at first diagnosis, 13.4 [10.0-21.8] years; 5944 [76%] male). Compared with unaffected individuals from the general population, people with TS or CTD had a 2-fold increased risk of experiencing any violent assault (sexual and nonsexual) (adjusted hazard ratio [aHR], 2.21; 95% CI, 2.00-2.43), a 3-fold increased risk of violent convictions (aHR, 3.13; 95% CI, 2.92-3.36), and a 1.6-fold increased risk of nonviolent crime convictions (aHR, 1.62; 95% CI, 1.54-1.71). Among people with TS or CTD, 37.0% (114 of 308; 95% CI, 31.6%-42.4%) of individuals who had experienced violent assault also had a violent crime conviction, compared with 17.9% (16 067 of 89 920; 95% CI, 17.6%-18.1%) in the general population. Exclusion of individuals with attention-deficit/hyperactivity disorder and substance use disorders partially attenuated the associations. Similarly, within-sibling models attenuated but did not eliminate the associations (any violent assault: aHR, 1.32; 95% CI, 1.08-1.61; violent crime: aHR, 2.23; 95% CI, 1.86-2.67; nonviolent crime: aHR, 1.34; 95% CI, 1.20-1.50).

Conclusions and Relevance

Results of this cohort study suggest that most individuals with TS or CTD are not assaulted nor are perpetrators of crime. However, individuals with TS or CTD diagnosed in specialist settings were more likely to both experience violent assault and be perpetrators of violence compared with the general population. The risk was highest in individuals with comorbid attention-deficit/hyperactivity disorder and substance use disorders. The increased risk found in specialty clinics will need to be better understood in the general population.

Associations between use of psychotropic medications and use of hormonal contraception among girls and women aged 15-49 years in Finland: a nationwide, register-based, matched case-control study

OBJECTIVES

The relationship between the use of contraception and of psychiatric medications is understudied. We examined whether the current and past use of psychotropic medications is associated with the use and type of hormonal contraception (HC).

DESIGN

Nationwide register-based matched case-control study.

SETTINGS

All fertile-aged (15-49 years) girls and women living in Finland in 2017; data from several national registers.

PARTICIPANTS

294 356 girls and women with a redeemed prescription of HC in 2017, and their same-sized control group of non-users (n=294 356) identified through the Prescription Centre.

MAIN OUTCOME MEASURES

Associations between the use of psychotropic medications and the use of HC, and the type of HC tested in logistic regression models.

RESULTS

Altogether 19.5% of the HC users, and 18% of the HC non-users received at least one prescription for a psychotropic medication in 2017. Among HC users, the proportions of occasional and regular users of psychotropic medications in 2013-2016 were 4.5% and 14.8%, while among HC non-users the respective figures were 4.3% and 14.6%, respectively. In multivariable logistic regression models both the use of psychotropic medications in 2017, and their occasional or regular use between 2013-2016 were associated with higher odds of HC use, although with small to very small effect sizes (ORs between 1.37 and 1.06 and 95% CIs 1.22 to 1.53, and 1.03 to 1.09, respectively). After adjustment for covariates, when fixed combinations of progestogens and oestrogens for systemic use was the reference category, women using almost any class of psychotropic medications had higher odds of using other types of HC.

CONCLUSIONS

Fertile-aged girls and women with current and past use of psychotropic medications have higher odds of using HC, with a specific pattern in the type of contraceptives used. Further research is warranted to examine whether our observations indicate a reduction of unwanted pregnancies in women with psychiatric disorders.

Association of parental substance misuse with offspring substance misuse and criminality: a genetically informed register-based study

BACKGROUND

Genetically informed studies have provided mixed findings as to what extent parental substance misuse is associated with offspring substance misuse and antisocial behavior due to shared environmental and genetic factors.

METHODS

We linked data from nationwide registries for a cohort of 2 476 198 offspring born in Sweden 1958-1995 and their parents. Substance misuse was defined as International Classification of Diseases diagnoses of alcohol/drug use disorders or alcohol/drug-related criminal convictions. Quantitative genetic offspring-of-siblings analyses in offspring of monozygotic and dizygotic twin, full-sibling, and half-sibling parents were conducted.

RESULTS

Both maternal and paternal substance misuse were robustly associated with offspring substance misuse [maternal adjusted hazard ratio (aHR) = 1.83 (95% confidence interval (CI) 1.80-1.87); paternal aHR = 1.96 (1.94-1.98)] and criminal convictions [maternal aHR = 1.56 (1.54-1.58); paternal aHR = 1.66 (1.64-1.67)]. Additive genetic effects explained 42% (95% CI 25-56%) and 46% (36-55%) of the variance in maternal and paternal substance misuse, respectively, and between 36 and 44% of the variance in substance misuse and criminality in offspring. The associations between parental substance misuse and offspring outcomes were mostly due to additive genetic effects, which explained 54-85% of the parent-offspring covariance. However, both nuclear and extended family environmental factors also contributed to the associations, especially with offspring substance misuse.

CONCLUSIONS

Our findings from a large offspring-of-siblings study indicate that shared genetic influences mostly explain the associations between parental substance misuse and both offspring substance misuse and criminality, but we also found evidence for the contribution of environmental factors shared by members of nuclear and extended families.

Association of selective serotonin re-uptake inhibitor (SSRI) treatment with acute substance misuse outcomes

BACKGROUND AND AIMS

Selective serotonin reuptake inhibitors (SSRIs) are widely prescribed medications for patients with anxiety/depression. These patients often have problems with substance use, but it remains unclear whether the risk of substance misuse is influenced by SSRI treatment. We aimed to determine whether SSRI treatment is associated with a decreased risk of acute substance misuse-related outcomes.

DESIGN

Cohort study following individuals through Swedish nation-wide registers between July 2005 and December 2013 and comparing the risk of substance misuse outcomes during periods on- versus off-treatment within the same individual.

SETTING

Swedish general population.

PARTICIPANTS

Individuals with a newly dispensed prescription of SSRIs between July 2006 and December 2013 and an ICD-10 diagnosis of anxiety/depressive disorder before the first treatment initiation. The cohort included 146 114 individuals (60.7% women).

MEASUREMENTS

Substance misuse outcomes included ICD-10 diagnoses of acute intoxications (F10.0-F19.0), accidental poisonings by alcohol or drugs (X41-X42, X45-X46) and substance-related criminal offenses.

FINDINGS

The absolute rate of substance misuse increased sharply before the onset of SSRI treatment and decreased after treatment initiation. Stratified Cox regression models showed an elevated risk [hazard ratio (HR) = 1.70, 95% confidence interval (CI) = 1.62-1.78] of substance misuse outcomes during a 1-month period preceding treatment initiation, compared with the reference period of more than 1 month before treatment start. The on-treatment estimates (1-30 days, HR = 1.29, 95% CI = 1.23-1.37; 31-120 days, HR = 1.30, 95% CI = 1.24-1.35; and > 120 days, HR = 1.24, 95% CI = 1.18-1.30 after treatment initiation] were consistently lower than the 1-month pre-treatment estimate, but still elevated compared with the reference period.

CONCLUSIONS

For people with anxiety/depression, the risk of substance misuse appears to be particularly elevated immediately before initiating selective serotonin reuptake inhibitor (SSRI) treatment, which may reflect the emergence or worsening of substance use problems concurrently with anxiety/depression. SSRI treatment appears to be associated with a lower risk of substance misuse compared with the 1-month period preceding treatment initiation, but causality remains uncertain.

Educational attainment of same-sex and opposite-sex dizygotic twins: An individual-level pooled study of 19 twin cohorts

Comparing twins from same- and opposite-sex pairs can provide information on potential sex differences in a variety of outcomes, including socioeconomic-related outcomes such as educational attainment. It has been suggested that this design can be applied to examine the putative role of intrauterine exposure to testosterone for educational attainment, but the evidence is still disputed. Thus, we established an international database of twin data from 11 countries with 88,290 individual dizygotic twins born over 100 years and tested for differences between twins from same- and opposite-sex dizygotic pairs in educational attainment. Effect sizes with 95% confidence intervals (CI) were estimated by linear regression models after adjusting for birth year and twin study cohort. In contrast to the hypothesis, no difference was found in women (β = -0.05 educational years, 95% CI -0.11, 0.02). However, men with a same-sex co-twin were slightly more educated than men having an opposite-sex co-twin (β = 0.14 educational years, 95% CI 0.07, 0.21). No consistent differences in effect sizes were found between individual twin study cohorts representing Europe, the USA, and Australia or over the cohorts born during the 20th century, during which period the sex differences in education reversed favoring women in the latest birth cohorts. Further, no interaction was found with maternal or paternal education. Our results contradict the hypothesis that there would be differences in the intrauterine testosterone levels between same-sex and opposite-sex female twins affecting education. Our findings in men may point to social dynamics within same-sex twin pairs that may benefit men in their educational careers.

Voluntary Adolescent-Onset Alcohol Drinking Fails to Influence Alcohol Consumption or Anxiety-Like Behaviour in Adulthood in Female Alcohol-Preferring Rats

AIMS

Alcohol exposure during adolescence is associated with both increased risk for alcohol use disorders and anxiety in adulthood. Our present experiments examined this association using alcohol-preferring AA (Alko Alcohol) rats selected for high voluntary alcohol drinking.

METHODS

Two groups of female AA rats acquired alcohol drinking at different ages. We gave the adolescent-onset group free choice to 10% alcohol and water for seven weeks, starting on post-natal day 42 (PND 42), whereas the adult-onset group started drinking alcohol on PND 112. After the 7-week drinking, we withdrew the adolescent group from alcohol for two weeks, followed by another voluntary 7-week drinking period, started at the same age as the adult-onset group. We assessed anxiety-like behaviour repeatedly during alcohol drinking with open field and elevated plus maze tests. At the end of alcohol drinking, we also tested the rats using the light/dark box, stress-induced body temperature test and social dominance test.

RESULTS

During the first 7-week alcohol drinking, adolescent rats exhibited significantly slower acquisition of alcohol drinking and lower alcohol preference than the adult-onset group. However, when tested at the same age as the adult-onset rats, they displayed identical alcohol intake and preference. We found no alcohol-induced effects on anxiety- or stress-related behaviour in the experimental groups at any time points.

CONCLUSIONS

These data show that the genetically determined phenotype of high alcohol drinking of the female alcohol-preferring AA rats is not associated with a predisposition to develop anxiety-like behaviour following voluntary alcohol exposure, even when initiated during adolescence.

Longitudinal Associations of Childhood Internalizing Psychopathology With Substance Misuse: A Register-Based Twin and Sibling Study

OBJECTIVE

The pathways from internalizing psychopathology to substance misuse remain largely unclear. We estimated associations between childhood internalizing problems and subsequent substance misuse in 2 family-based samples. We also investigated sex differences and the role of externalizing comorbidity.

METHOD

We studied associations of childhood internalizing psychopathology with register-based substance misuse after age 13 years. Sample 1 included all individuals born in Sweden from 1984 to 2000 (N = 1,768,516). Depressive and anxiety disorders were included as register-based International Classification of Diseases Ninth Revision (ICD-9) or Tenth Revision (ICD-10) diagnoses before age 13. Sample 2 was a subsample within the population sample, the Child and Adolescent Twin Study in Sweden (CATSS) twin cohort (n = 12,408; born 1992-1998), with mood and anxiety problems assessed at age 9/12 by parents. In both samples, substance misuse was defined as an ICD-9/10 alcohol/drug use disorder or an alcohol/drug-related criminal conviction until December 2013. To account for familial effects, stratified analyses were conducted within siblings and twin pairs.

RESULTS

In the population sample, both depressive (hazard ratio [HR] = 2.75, 95% CI = 2.36-3.20) and anxiety disorders (HR = 1.52, 95% CI = 1.35-1.73) were associated with substance misuse. Childhood mood problems (HR = 2.28, 95% CI = 1.69-3.08) were associated with substance misuse in the CATSS sample. The associations were partially explained by familial factors, and comorbid externalizing disorders explained the associations in men but not in women.

CONCLUSION

Childhood mood problems were associated with substance misuse, but familial factors shared by siblings partially explained the associations. The relationship of anxiety with substance misuse was complex and depended on measurement and the type of anxiety disorder. Internalizing problems may be especially important for substance misuse risk in women.

Population-level indicators associated with hormonal contraception use: a register-based matched case-control study

Background

Monitoring factors related to hormonal contraception (HC) use is essential to evaluating public health strategies and promoting access to contraception. We aimed to examine municipal social and health indicators of HC use at the population level, and to identify patterns of inequality across Finnish municipalities.

Methods

We identified all women (15–49 years) with a redeemed HC prescription in Finland in 2017 (n = 294,445), and a control group of non-users. Municipal social and health indicators at the population level were retrieved from the nationwide Statistics and Indicator Bank. Differences between the groups across 309 municipalities were calculated, and associations of municipal-specific proportions of HC users with municipal-specific indicators were studied using LASSO (Least Absolute Shrinkage and Selection Operator) models.

Results

Sociodemographic differences between HC users and non-users were non-homogenous across municipalities. Indicators positively associated with HC use included: larger population and higher proportions of population aged 16–24 years, of household-dwelling units with one person, of persons with higher education, and of divorces among those aged 25–64. Lower HC use was associated with higher proportions of Swedish-speaking population, of those aged 7–15 years, of young people not in education/training, and of household-dwelling units in overcrowded conditions. Lower HC use was also associated with indicators of outpatient and inpatient healthcare, and of municipal finances in welfare and healthcare.

Conclusions

Sociodemographic differences in relation to HC use exist across Finnish municipalities. Municipal indicators of social structure, health and welfare, and investment in and use of healthcare services are related to HC use.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-021-10512-6.

Association of Tourette Syndrome and Chronic Tic Disorder With Subsequent Risk of Alcohol- or Drug-Related Disorders, Criminal Convictions, and Death: A Population-Based Family Study

BACKGROUND

It remains unclear if individuals with Tourette syndrome (TS) or chronic tic disorder (CTD) have an elevated risk of subsequent substance misuse.

METHODS

In this population-based cohort study, we investigated the association between ICD diagnoses of TS/CTD and substance misuse outcomes, accounting for psychiatric comorbidity and familial factors. The cohort included all individuals living in Sweden at any time between January 1, 1973, and December 31, 2013. Substance misuse outcomes were defined as an ICD code of substance use-related disorder or cause of death, or as a substance use-related criminal conviction in the nationwide registers.

RESULTS

The cohort included 14,277,199 individuals, of whom 7832 had a TS/CTD diagnosis (76.3% men). TS/CTD was associated with an increased risk of any subsequent substance misuse outcomes (adjusted hazard ratio [aHR], 3.11; 95% confidence interval [CI], 2.94-3.29), including alcohol-related disorder (aHR, 3.45; 95% CI, 3.19-3.72), drug-related disorder (aHR, 6.84; 95% CI, 6.32-7.40), substance-related criminal convictions (aHR, 2.56; 95% CI, 2.36-2.77), and substance-related death (aHR, 2.54; 95% CI, 1.83-3.52). Excluding psychiatric comorbidities had little effect on the magnitude of the associations, with the exception of attention-deficit/hyperactivity disorder, which attenuated the risk of any substance misuse outcomes (aHR, 2.00; 95% CI, 1.82-2.19). The risk of any substance misuse outcomes in individuals with TS/CTD was substantially attenuated but remained significant when compared with their unaffected siblings (aHR, 1.74; 95% CI, 1.53-1.97).

CONCLUSIONS

TS/CTD were associated with various types of subsequent substance misuse outcomes, independently of psychiatric comorbidity and familial factors shared between siblings. Screening for drug and alcohol use should become part of the standard clinical routines, particularly in patients with comorbid attention-deficit/hyperactivity disorder.

Associations between hormonal contraception use, sociodemographic factors and mental health: a nationwide, register-based, matched case-control study

OBJECTIVES

Sociodemographic and mental health characteristics are associated with contraceptive choices. We aimed to describe the sociodemographic, reproductive and mental health characteristics of all fertile-aged women in Finland who used hormonal contraception (HC) in 2017.

DESIGN

A nationwide, register-based study.

SETTING

All women living in Finland in 2017; data from the Care Register of Health Care, Medical Birth Register, Population Register Centre, Prescription Centre, Register of Induced Abortions.

PARTICIPANTS

All women aged 15-49 with one redeemed HC prescription in 2017 (n=294 356), and a same-sized, age-matched and residence-matched, control group of non-users.

OUTCOMES

Rates of HC use; associations between HC use and mental disorders, sociodemographic and reproductive characteristics.

RESULTS

25.8% of women aged 15-49 years used HC. Women with the lowest socioeconomic levels had lower odds of using HC than women with upper-level statuses (OR, 95% CI students: 0.97, 0.94 to 0.99; entitled to pension: 0.66, 0.63 to 0.69; other: 0.87, 0.85 to 0.89; unknown: 0.90, 0.85 to 0.90). Women with the highest education (secondary: 1.46, 1.43 to 1.48; tertiary: 1.64, 1.58 to 1.70; academic: 1.60, 1.56 to 1.63) and income (second quarter: 1.57, 1.54 to 1.60; third quarter: 1.85, 1.82 to 1.89; fourth quarter: 2.01, 1.97 to 2.06), and unmarried women had higher odds of using HC than women with the lowest education and income levels, and married (0.61, 0.60 to 0.62), divorced (0.86, 0.84 to 0.88), widowed (0.73, 0.65 to 0.83) or other marital status women (0.26, 0.22 to 0.30).Parous women (0.70, 0.69 to 0.71), those with previous induced abortion(s) (0.91, 0.89 to 0.92) or recent eating (0.68, 0.62 to 0.75) or personality (0.89, 0.79 to 0.97) disorders had lower odds of HC use. Absolute risk differences between women with and without mental disorders ranged from 3.1% (anxiety disorders) to 10.1% (eating disorders).

CONCLUSIONS

A quarter of the fertile-aged women use HC in Finland. Sociodemographic disparities persist in relation to HC use, although of small effect size. HC use is less common among women suffering from severe to moderate psychiatric disorders, especially eating disorders.

Physical Activity and Academic Performance: Genetic and Environmental Associations

INTRODUCTION

Physical activity and academic performance are believed to be associated. Though both traits are partially heritable, it remains unclear whether these traits also share a genetic and/or environmental background in common. We aimed to examine to what extent leisure time physical activity and academic performance share genetic and environmental effects from early adolescence to young adulthood.

METHODS

Participants were Finnish twins (2543-2693 individuals/study wave) who reported their leisure-time physical activity at ages 12, 14, 17, and 24 yr. Academic performance was assessed with teacher-reported grade point averages at ages 12 and 14 yr and by self-reported educational levels at ages 17 and 24 yr. Bivariate quantitative genetic modeling at each age and between different ages was performed to decompose the trait correlation between academic performance and physical activity into genetic and environmental components.

RESULTS

The trait correlations between leisure-time physical activity and academic performance were positive, but modest at most (rtrait = 0.08-0.22 in males, and 0.07-0.18 in females). The genetic correlations between leisure-time physical activity and academic performance were higher than the trait correlations (rA = 0.17-0.43 in males, and 0.15-0.25 in females). Common genetic influences explained 43% to 100% of the trait correlations. Environmental influences shared by cotwins between leisure-time physical activity and academic performance were also correlated (rC = 0.27-0.54 in males, and 0.21-0.69 in females) explaining 41% to 100% of the trait correlations. Unique environmental influences were correlated only in females (rE = 0.10-0.15).

CONCLUSIONS

Both common genetic background and shared family environment (i.e., familial background) partially account for the associations observed between leisure-time physical activity and academic performance. However, the estimates vary in magnitude by age.

Association of subclinical psychosis with suicidal ideation: A twin study

Subclinical psychosis, including schizotypal indicators and psychotic experiences, predicts future suicidal ideation. This relationship may reflect unmeasured confounding from environmental factors, genetic factors, or both. We used a genetically-informative twin design to understand if the association between subclinical psychosis and suicidal ideation is independent of shared genetic and environmental factors. We analysed cross-sectional associations of age-22 self-reported subclinical psychosis (positive, negative, and disorganised features) with suicidal ideation in twins participating in the FinnTwin12 study (maximum n = 1213). Then, we analysed the reverse association of age-14 suicidal ideation with age-22 subclinical psychosis. Associations were studied first among individuals and then within monozygotic (MZ) and dizygotic (DZ) pairs. Individual-level analyses showed that all subclinical psychosis factors were associated with suicidal ideation. In within-pair analyses, estimates of associations were lower for MZ pairs than DZ pairs, except for the negative schizotypy-suicidal ideation association where estimates were consistent across individual-level and within-pair analyses. Findings provide evidence that the association between negative features and suicide ideation is not explained by familial factors and may be causal, though the possibility of confounding by individual-specific environmental factors and reverse causation cannot be ruled out. The relationships of positive and disorganised subclinical psychosis features with suicidal ideation cannot be explained by confounding due to environmental factors shared between siblings, but their associations may be due to shared genetic factors.

Depressive symptoms predict smoking cessation in a 20-year longitudinal study of adult twins

Depression has been suggested to hinder smoking cessation, especially when co-occurring with nicotine dependence. The study aimed to examine the longitudinal association of depressive symptoms with smoking cessation among daily smokers. The study utilized adult Finnish twin cohort where 1438 daily smokers (mean age: 38.3, range: 33-45) in 1990 were re-examined for their smoking status in 2011. We assessed baseline depressive symptoms with the Beck Depression Inventory, and the self-reported smoking status at follow-up. The methods included multinomial logistic regression and time to event analyses, adjusted for multiple covariates (age, sex, marital status, social class, heavy drinking occasions, and health status) and smoking heaviness at baseline assessed by cigarettes per day (CPD). Additionally, within-twin-pair analyses were conducted. Results indicated that moderate/severe depressive symptoms at baseline were associated with a lower likelihood of smoking cessation two decades later. Adjusting for covariates, those with moderate/severe depressive symptoms (vs. no/minimal depressive symptoms) had 46% lower likelihood of quitting (relative risk ratio, RRR = 0.54, 95% CI: 0.30-0.96). After including CPD, the association of depressive symptoms with smoking cessation attenuated modestly (RRR = 0.62, 95% CI: 0.34-1.12). Further, time to event analysis for quitting year since baseline yielded similar findings. In the within-pair analysis, depressive symptoms were not associated with quitting smoking. The results suggest that reporting more depressive symptoms is associated with a lower likelihood of smoking cessation during a 20-year period. The baseline amount of smoking and familial factors partly explain the observed association. Smoking cessation programs should monitor depressive symptoms.

Genetic and environmental variation in educational attainment: an individual-based analysis of 28 twin cohorts

We investigated the heritability of educational attainment and how it differed between birth cohorts and cultural–geographic regions. A classical twin design was applied to pooled data from 28 cohorts representing 16 countries and including 193,518 twins with information on educational attainment at 25 years of age or older. Genetic factors explained the major part of individual differences in educational attainment (heritability: a² = 0.43; 0.41–0.44), but also environmental variation shared by co-twins was substantial (c² = 0.31; 0.30–0.33). The proportions of educational variation explained by genetic and shared environmental factors did not differ between Europe, North America and Australia, and East Asia. When restricted to twins 30 years or older to confirm finalized education, the heritability was higher in the older cohorts born in 1900–1949 (a² = 0.44; 0.41–0.46) than in the later cohorts born in 1950–1989 (a² = 0.38; 0.36–0.40), with a corresponding lower influence of common environmental factors (c² = 0.31; 0.29–0.33 and c² = 0.34; 0.32–0.36, respectively). In conclusion, both genetic and environmental factors shared by co-twins have an important influence on individual differences in educational attainment. The effect of genetic factors on educational attainment has decreased from the cohorts born before to those born after the 1950s.

Comorbidity of substance misuse with anxiety-related and depressive disorders: a genetically informative population study of 3 million individuals in Sweden

BACKGROUND

Causes of the comorbidity of substance misuse with anxiety-related and depressive disorders (anxiety/depression) remain poorly known. We estimated associations of substance misuse and anxiety/depression in the general population and tested them while accounting for genetic and shared environmental factors.

METHODS

We studied individuals born in Sweden 1968-1997 (n = 2 996 398) with follow-up in nationwide register data for 1997-2013. To account for familial effects, stratified analyses were conducted within siblings and twin pairs. Substance misuse was defined as ICD-10 alcohol or drug use disorder or an alcohol/drug-related criminal conviction. Three dimensions of ICD-10 anxiety and depressive disorders and a substance misuse dimension were identified through exploratory factor analysis.

RESULTS

Substance misuse was associated with a 4.5-fold (95% CI 4.50-4.58) elevated risk of lifetime generalized anxiety/depression, 4.7-fold (95% CI 4.63-4.82) elevated risk of panic disorder and agora/social phobia, and 2.9-fold elevated risk of phobias/OCD (95% CI 2.82-3.02) as compared to those without substance misuse. The associations were attenuated in within-family analyses but we found elevated risks in monozygotic twin pairs discordant for substance misuse as well as significant non-shared environmental correlations. The association between anxiety/depression and substance misuse was mainly driven by generalized anxiety/depression, whereas other anxiety/depression dimensions had minor or no independent associations with substance misuse.

CONCLUSIONS

Substance misuse and anxiety/depression are associated at the population level, and these associations are partially explained by familial liabilities. Our findings indicate a common genetic etiology but are also compatible with a potential partially causal relationship between substance misuse and anxiety/depression.

Which adolescent factors predict alcohol misuse in young adulthood? A co-twin comparisons study

BACKGROUND AND AIMS

Research on adolescent predictors of later alcohol misuse is typically conducted on samples of singletons, and associations may be confounded by between-family differences. To address potential confounding, we applied a co-twin comparison design to evaluate whether differences between co-twins in a wide array of adolescent risk factors predicted differences in young adult alcohol misuse.

DESIGN

Longitudinal study in which associations between characteristics of the sample as adolescents were used to predict young adult alcohol misuse in individual-level analyses and co-twin comparisons.

SETTING

Finland.

PARTICIPANTS

A total of 3402 individuals (1435 complete twin pairs; 36% monozygotic; 57% female) from the FinnTwin12 study.

MEASUREMENTS

The young adult alcohol misuse outcome was a composite score of alcohol use and intoxication frequency. Adolescent predictors included factor scores representing academic performance, substance use, externalizing problems, internalizing problems, peer environment, physical health and relationship with parents; and single measures tapping alcohol expectancies, life events and pubertal development.

FINDINGS

In individual-level analyses, individuals with higher adolescent substance use, externalizing problems, time with friends, peer deviance, sports involvement, sleeping difficulties, parental discipline, positive alcohol expectancies and difficulty of life events reported higher alcohol misuse in young adulthood (Ps < 0.019, R²  = 0.0003-0.0310%). Conversely, those with higher adolescent internalizing problems, parent-child relationship quality and time with parents reported lower alcohol misuse (Ps < 0021, R²  = 0.0018-0.0093%). The associations with adolescent substance use and alcohol expectancies remained significant in co-twin comparisons (Ps < 0.049, R²  = 0.0019-0.0314%). Further, academic performance emerged as a significant predictor, such that individuals with higher grades compared with their co-twin reported higher young adult alcohol misuse (Ps < 0.029, R²  = 0.0449-0.0533%).

CONCLUSIONS

Adolescent substance use, positive alcohol expectancies and higher academic performance appear to be robust predictors of later alcohol misuse.

Association of parental substance use disorder with offspring cognition: a population family-based study

AIMS

To assess whether parental substance use disorder (SUD) is associated with lower cognitive ability in offspring, and whether the association is independent of shared genetic factors.

DESIGN

A population family-based cohort study utilizing national Swedish registries. Linear regression with increased adjustment of covariates was performed in the full population. In addition, the mechanism of the association was investigated with children-of-sibling analyses using fixed-effects regression with three types of sibling parents with increasing genetic relatedness (half-siblings, full siblings and monozygotic twins).

SETTING AND PARTICIPANTS

A total of 3 004 401 people born in Sweden between 1951 and 1998.

MEASUREMENTS

The exposure variable was parental SUD, operationalized as having a parent with life-time SUD diagnosis or substance-related criminal conviction in the National Patient Register or Crime Register, respectively. Outcomes were cognitive test score at military conscription and final school grades when graduating from compulsory school. Covariates included in the analyses were sex, birth year, parental education, parental migration status and parental psychiatric comorbid diagnoses.

FINDINGS

In the full population, parental SUD was associated with decreased cognitive test stanine scores at conscription [4.56, 95% confidence interval (CI) = 4.55-4.57] and lower Z-standardized school grades (-0.43, 95% CI = -0.43 to -0.42) compared to people with no parental SUD (cognitive test: 5.17, 95% CI = 5.17-5.18; grades: 0.09, 95% CI = 0.08-0.09). There was evidence of a dose-response relationship, in that having two parents with SUD (cognitive test: 4.17, 95% CI = 4.15-4.20; grades: -0.83, 95% CI = -0.84 to -0.82) was associated with even lower cognitive ability than having one parent with SUD (cognitive test: 4.60, 95% CI = 4.59-4.60; grades: -0.38, 95% CI = -0.39 to -0.380). In the children-of-siblings analyses when accounting for genetic relatedness, these negative associations were attenuated, suggestive of shared underlying genetic factors.

CONCLUSIONS

There appear to be shared genetic factors between parental substance use disorder (SUD) and offspring cognitive function, suggesting that cognitive deficits may constitute a genetically transmitted risk factor in SUD.

Nation-wide profile of women using hormonal contraception in Finland in 2017

Background

Up to 69% of European women use contraception. Nordic countries have traditionally high levels of contraception use, of welfare and social equality. However, the uneven population distribution across the Finnish territory makes the easiness of access to health care structures and trained professionals an important issue in relation to effective contraception use. Understanding the patterns of contraception prescription and their underlying determinants is crucial to guarantee the best contraceptive option for each woman.

Methods

In Finland, users of hormonal contraception (HC) can be identified from register records only starting from 2017. This nationwide, register-based study includes all women with at least one HC prescription in 2017, and a reference cohort of non-users, matched by age and municipality. Through linkages to Finnish National Registers we retrieved sociodemographic data. We calculated national and regional rates and distributions, and compared distributions with t-test, Kruskal Wallis or Chi-squared test.

Results

The HC cohort included 294445 women aged 15-49 years (mean 28.9, SD 8.6), 25.8% of Finnish women of that age range. The majority of them were unmarried (71.8%) and employed (71.6%). Compared to non-users, HC users were more often unmarried, a cohabiting couple without common children, employed, had upper secondary or bachelor level education, and higher annual income (p &lt; 0.001). Differences between HC users and non-users were non-homogenous across 70 Finnish regions.

Conclusions

These preliminary results show different sociodemographic correlates of HC use across Finnish regions. Our findings will guide public health strategies aimed at guaranteeing the best contraceptive option for each woman across the whole country.

Key messages

Sociodemographic correlates of HC use differ across Finnish regions. These differences may reflect differences in access to health care services, in prescribers’ characteristics and in HC methods.

FinnTwin12 Cohort: An Updated Review

This review offers an update on research conducted with FinnTwin12 (FT12), the youngest of the three Finnish Twin Cohorts. FT12 was designed as a two-stage study. In the first stage, we conducted multiwave questionnaire research enrolling all eligible twins born in Finland during 1983-1987 along with their biological parents. In stage 2, we intensively studied a subset of these twins with in-school assessments at age 12 and semistructured poly-diagnostic interviews at age 14. At baseline, parents of intensively studied twins were administered the adult version of the interview. Laboratory studies with repeat interviews, neuropsychological tests, and collection of DNA were made of intensively studied twins during follow-up in early adulthood. The basic aim of the FT12 study design was to obtain information on individual, familial and school/neighborhood risks for substance use/abuse prior to the onset of regular tobacco and alcohol use and then track trajectories of use and abuse and their consequences into adulthood. But the longitudinal assessments were not narrowly limited to this basic aim, and with multiwave, multirater assessments from ages 11 to 12, the study has created a richly informative data set for analyses of gene-environment interactions of both candidate genes and genomewide measures with measured risk-relevant environments. Because 25 years have elapsed since the start of the study, we are planning a fifth-wave follow-up assessment.

Polygenic risk for alcohol misuse is moderated by romantic partnerships

BACKGROUND AND AIMS

Previous twin research suggests relationship status can moderate underlying genetic liability towards alcohol misuse. This paper examined: (1) whether genome-wide polygenic scores (GPS) for alcohol consumption are associated with alcohol misuse; (2) whether these GPS are moderated by romantic relationships (gene-environment interaction; G × E) and (3) whether G × E results are consistent across sex.

DESIGN

Linear mixed-effects models were used to test associations between genome-wide polygenic scores, relationship status and alcohol use/misuse.

SETTING

Finnish twins born between 1983 and 1987 identified through Finland's central population registry.

PARTICIPANTS

An intensively studied subset of Finnish Twin Study (FinnTwin12) during the young adult phase (aged 20-26 years). The analytical sample includes those with complete interview and genetic data (n = 1201).

MEASUREMENTS

Key measurements included involvement in a romantic partnership, drinking frequency, intoxication frequency and DSM-IV alcohol dependence (AD) symptoms. Genome-wide polygenic scores (GPS) were created from available summary statistics from a large genome-wide association study (GWAS) of drinks per week.

RESULTS

GPS predicted drinking frequency [b = 0.109; 95% confidence interval (CI) = 0.050, 0.168], intoxication frequency (b = 0.111; 95% CI = 0.054, 0.168) and AD symptoms (b = 0.123; 95% CI = 0.064, 0.182). Having a romantic relationship negatively influenced the association between GPS and drinking frequency (b = -0.105; 95% CI = -0.211, -0.001), intoxication frequency (b = -0.118; 95% CI = -0.220, -0.016) and AD symptoms (b = -0.119; 95% CI = -0.229, -0.009). There was a three-way interaction between sex, relationship status and GPS for intoxication frequency (b = 0.223; 95% CI = 0.013, 0.433), such that the reduced association between GPS and intoxication frequency for those in a relationship was only apparent in males. We found no evidence of three-way interactions for drinking frequency or AD symptoms.

CONCLUSIONS

Being in a romantic relationship reduced the association between genetic predisposition and drinking, high-risk drinking and alcohol problems. However, for high-risk drinking the protective effect was limited to males, mapping onto earlier findings suggesting that males benefit more from romantic partnerships.

Is diversity of leisure-time sport activities associated with low back and neck-shoulder region pain? A Finnish twin cohort study

This study investigates cross-sectional and longitudinal associations between the diversity of leisure-time sport activities and the frequencies of low back pain (LBP) and neck-shoulder region pain (NSP) in twins, including a cross-sectional within-pair design to adjust for potential familial confounding.

Finnish twins born in 1975–79 (FinnTwin16 study) reported participation in leisure-time sport activities at the mean ages of 17 (1992–96) (n = 5096, 54% females) and 34 years (2010−12) (n = 3731, 57% females). Diversity assessed as the number of sport activities was categorized as 1, 2, 3, 4, and ≥ 5, excluding inactive individuals. The frequencies of LBP (n = 3201) and NSP (n = 3207), reported at age 34, were categorized as never/seldom, monthly, or weekly pain. Cross-sectional and longitudinal individual-based associations between the number of sport activities and the frequency of LBP and NSP were investigated with multinomial logistic regression analyses, adjusting for multiple confounders. Cross-sectionally, participation in ≥5 sport activities, compared to 1 sport, was associated with significantly less weekly LBP (OR = 0.63, 95%CI = 0.43–0.90), but not with NSP. Longitudinally, participation in several sport activities in adolescence had no significant association with LBP or NSP in adulthood. Cross-sectional within-pair analyses were conducted among twin pairs discordant for LBP (n = 507) and NSP (n = 579). The associations between monozygotic and dizygotic twin pairs were similar in LBP-discordant pairs but differed within NSP-discordant pairs.

Participation in ≥5 sport activities in adulthood may be associated with less weekly LBP, but not with monthly LBP or the frequency of NSP. However, within-pair analyses for NSP suggest confounding due to shared familial factors.

•

Participation in more sport activities is associated with less low back pain (LBP).

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More sport activities is not associated with neck-shoulder pain (NSP).

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Shared familial factors may confound the association between sport activities and NSP.

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Number of sport activities in adolescence did not predict LBP or NSP in adulthood.

Testing the reciprocal association between smoking and depressive symptoms from adolescence to adulthood: A longitudinal twin study

BACKGROUND

Longitudinal studies enhance understanding of the complex reciprocal relationship between smoking and depression from adolescence to young adulthood. Examining bi-directional associations between cigarette smoking and depressive symptoms in a genetically informative twin design can help to understand whether the associations are independent of shared genetic and environmental factors.

METHODS

We analyzed longitudinal data on smoking and depressive symptoms in twins participating in the adolescent (mean age 17.5) and young adult (mean age 21.9) surveys of the FinnTwin12 study (maximum N = 2,954 individuals; 1,154 twin pairs). At both waves, self-reported depressive symptoms, assessed with the 10-item version of the General Behavior Inventory (GBI), and smoking status were analyzed. The bi-directional associations were first studied among individuals and then within monozygotic and dizygotic twin pairs.

RESULTS

When adjusted for multiple covariates and baseline depressive symptoms, daily smokers at age 17 had higher depressive symptom scores at age 22 than never smokers (Incidence Rate Ratio = 1.17, 95% CI: 1.03-1.33). Similarly, when adjusted for covariates and baseline smoking, higher score in GBI at age 17 was associated with an increased likelihood of being a non-daily (Relative Risk Ratio (RRR) = 1.06, 95% CI: 1.01-1.11) or daily (RRR = 1.05, 95% CI: 1.00-1.10) smoker at age 22. No associations were found in within-pair analyses, suggesting that the individual-level association is explained by shared familial liabilities.

CONCLUSION

During the developmental period from adolescence to adulthood, cigarette smoking and depressive symptoms are reciprocally associated. However, these associations are confounded by shared genetic and other familial liabilities.

Parental Education and Genetics of BMI from Infancy to Old Age: A Pooled Analysis of 29 Twin Cohorts

OBJECTIVE

The objective of this study was to analyze how parental education modifies the genetic and environmental variances of BMI from infancy to old age in three geographic-cultural regions.

METHODS

A pooled sample of 29 cohorts including 143,499 twin individuals with information on parental education and BMI from age 1 to 79 years (299,201 BMI measures) was analyzed by genetic twin modeling.

RESULTS

Until 4 years of age, parental education was not consistently associated with BMI. Thereafter, higher parental education level was associated with lower BMI in males and females. Total and additive genetic variances of BMI were smaller in the offspring of highly educated parents than in those whose parents had low education levels. Especially in North American and Australian children, environmental factors shared by co-twins also contributed to the higher BMI variation in the low education level category. In Europe and East Asia, the associations of parental education with mean BMI and BMI variance were weaker than in North America and Australia.

CONCLUSIONS

Lower parental education level is associated with higher mean BMI and larger genetic variance of BMI after early childhood, especially in the obesogenic macro-environment. The interplay among genetic predisposition, childhood social environment, and macro-social context is important for socioeconomic differences in BMI.

Birth cohort effects on the quantity and heritability of alcohol consumption in adulthood: a Finnish longitudinal twin study

AIMS

To estimate birth cohort effects on alcohol consumption and abstinence in Finland and to test differences between birth cohorts in genetic and environmental sources of variation in Finnish adult alcohol use.

DESIGN

The Older Finnish Twin Cohort longitudinal survey study 1975-2011.

SETTING

Finland.

PARTICIPANTS

A total of 26 121 same-sex twins aged 18-95 years (full twin pairs at baseline n = 11 608).

MEASUREMENTS

Outcome variables were the quantity of alcohol consumption (g/month) and abstinence (drinking zero g/month). Predictor variables were 10-year birth cohort categories and socio-demographic covariates. In quantitative genetic models, two larger cohorts (born 1901-20 and 1945-57) were compared.

FINDINGS

Multi-level models in both sexes indicated higher levels of alcohol consumption in more recent birth cohorts and lower levels in earlier cohorts, compared with twins born 1921-30 (all P < 0.003). Similarly, compared with twins born 1921-30, abstaining was more common in earlier and less common in more recent cohorts (all P < 0.05), with the exception of men born 1911-20. Birth cohort differences in the genetic and environmental variance components in alcohol consumption were found: heritability was 21% [95% confidence interval (CI) = 0-56%] in the earlier-born cohort of women [mean age 62.8, standard deviation (SD) = 5.3] and 51% (95% CI = 36-56%) in a more recent cohort (mean age 60.2, SD = 3.7) at the age of 54-74. For men, heritability was 39% (95% CI = 27-45%) in both cohorts. In alcohol abstinence, environmental influences shared between co-twins explained a large proportion of variation in the earlier-born cohort (43%, 95% CI = 23-63%), whereas non-shared environmental (54%, 95% CI = 39-72%) and additive genetic influences (40%, 95% CI = 13-61%) were more important among more recent cohorts of men and women.

CONCLUSION

The contribution of genetic and environmental variability to variability in alcohol consumption in the Finnish population appears to vary by birth cohort.

Association of current and former smoking with body mass index: A study of smoking discordant twin pairs from 21 twin cohorts

Background

Smokers tend to weigh less than never smokers, while successful quitting leads to an increase in body weight. Because smokers and non-smokers may differ in genetic and environmental family background, we analysed data from twin pairs in which the co-twins differed by their smoking behaviour to evaluate if the association between smoking and body mass index (BMI) remains after controlling for family background.

Methods and findings

The international CODATwins database includes information on smoking and BMI measured between 1960 and 2012 from 156,593 twin individuals 18–69 years of age. Individual-based data (230,378 measurements) and data of smoking discordant twin pairs (altogether 30,014 pairwise measurements, 36% from monozygotic [MZ] pairs) were analysed with linear fixed-effects regression models by 10-year periods. In MZ pairs, the smoking co-twin had, on average, 0.57 kg/m² lower BMI in men (95% confidence interval (CI): 0.49, 0.70) and 0.65 kg/m² lower BMI in women (95% CI: 0.52, 0.79) than the never smoking co-twin. Former smokers had 0.70 kg/m² higher BMI among men (95% CI: 0.63, 0.78) and 0.62 kg/m² higher BMI among women (95% CI: 0.51, 0.73) than their currently smoking MZ co-twins. Little difference in BMI was observed when comparing former smoking co-twins with their never smoking MZ co-twins (0.13 kg/m², 95% CI 0.04, 0.23 among men; -0.04 kg/m², 95% CI -0.16, 0.09 among women). The associations were similar within dizygotic pairs and when analysing twins as individuals. The observed series of cross-sectional associations were independent of sex, age, and measurement decade.

Conclusions

Smoking is associated with lower BMI and smoking cessation with higher BMI. However, the net effect of smoking and subsequent cessation on weight development appears to be minimal, i.e. never more than an average of 0.7 kg/m².

Association between birth weight and educational attainment: an individual-based pooled analysis of nine twin cohorts

BACKGROUND

There is evidence that birth weight is positively associated with education, but it remains unclear whether this association is explained by familial environmental factors, genetic factors or the intrauterine environment. We analysed the association between birth weight and educational years within twin pairs, which controls for genetic factors and the environment shared between co-twins.

METHODS

The data were derived from nine twin cohorts in eight countries including 6116 complete twin pairs. The association between birth weight and educational attainment was analysed both between individuals and within pairs using linear regression analyses.

RESULTS

In between-individual analyses, birth weight was not associated with educational years. Within-pairs analyses revealed positive but modest associations for some sex, zygosity and birth year groups. The greatest association was found in dizygotic (DZ) men (0.65 educational years/kg birth weight, p=0.006); smaller effects of 0.3 educational years/kg birth weight were found within monozygotic (MZ) twins of both sexes and opposite-sex DZ twins. The magnitude of the associations differed by birth year in MZ women and opposite-sex DZ twins, showing a positive association in the 1915-1959 birth cohort but no association in the 1960-1984 birth cohort.

CONCLUSION

Although associations are weak and somewhat inconsistent, our results suggest that intrauterine environment may play a role when explaining the association between birth weight and educational attainment.

Polygenic Risk Score Prediction of Alcohol Dependence Symptoms Across Population-Based and Clinically Ascertained Samples

BACKGROUND

Despite consistent evidence of the heritability of alcohol use disorders (AUDs), few specific genes with an etiological role have been identified. It is likely that AUDs are highly polygenic; however, the etiological pathways and genetic variants involved may differ between populations. The aim of this study was thus to evaluate whether aggregate genetic risk for AUDs differed between clinically ascertained and population-based epidemiological samples.

METHODS

Four independent samples were obtained: 2 from unselected birth cohorts (Avon Longitudinal Study of Parents and Children [ALSPAC], N = 4,304; FinnTwin12 [FT12], N = 1,135) and 2 from families densely affected with AUDs, identified from treatment-seeking patients (Collaborative Study on the Genetics of Alcoholism, N = 2,097; Irish Affected Sib Pair Study of Alcohol Dependence, N = 706). AUD symptoms were assessed with clinical interviews, and participants of European ancestry were genotyped. Genomewide association was conducted separately in each sample, and the resulting association weights were used to create polygenic risk scores in each of the other samples (12 total discovery-validation pairs), and from meta-analyses within sample type. We then tested how well these aggregate genetic scores predicted AUD outcomes within and across sample types.

RESULTS

Polygenic scores derived from 1 population-based sample (ALSPAC) significantly predicted AUD symptoms in another population-based sample (FT12), but not in either clinically ascertained sample. Trend-level associations (uncorrected p < 0.05) were found for polygenic score predictions within sample types but no or negative predictions across sample types. Polygenic scores accounted for 0 to 1% of the variance in AUD symptoms.

CONCLUSIONS

Though preliminary, these results provide suggestive evidence of differences in the genetic etiology of AUDs based on sample characteristics such as treatment-seeking status, which may index other important clinical or demographic factors that moderate genetic influences. Although the variance accounted for by genomewide polygenic scores remains low, future studies could improve gene identification efforts by amassing very large samples, or reducing genetic heterogeneity by informing analyses with other phenotypic information such as sample characteristics. Multiple complementary approaches may be needed to make progress in gene identification for this complex disorder.

Incorporating Functional Genomic Information to Enhance Polygenic Signal and Identify Variants Involved in Gene-by-Environment Interaction for Young Adult Alcohol Problems

BACKGROUND

Characterizing aggregate genetic risk for alcohol misuse and identifying variants involved in gene-by-environment (G × E) interaction effects has so far been a major challenge. We hypothesized that functional genomic information could be used to enhance detection of polygenic signal underlying alcohol misuse and to prioritize identification of single nucleotide polymorphisms (SNPs) most likely to exhibit G × E effects.

METHODS

We examined these questions in the young adult FinnTwin12 sample (n = 1,170). We used genomewide association estimates from an independent sample to derive 2 types of polygenic scores for alcohol problems in FinnTwin12. Genomewide polygenic scores included all SNPs surpassing a designated p-value threshold. DNase polygenic scores were a subset of the genomewide polygenic scores including only variants in DNase I hypersensitive sites (DHSs), which are open chromatin marks likely to index regions with a regulatory function. We conducted parallel analyses using height as a nonpsychiatric model phenotype to evaluate the consistency of effects. For the G × E analyses, we examined whether SNPs in DHSs were overrepresented among SNPs demonstrating significant G × E effects in an interaction between romantic relationship status and intoxication frequency.

RESULTS

Contrary to our expectations, we found that DNase polygenic scores were not more strongly predictive of alcohol problems than conventional polygenic scores. However, variants in DNase polygenic scores had per-SNP effects that were up to 1.4 times larger than variants in conventional polygenic scores. This same pattern of effects was also observed in supplementary analyses with height. In G × E models, SNPs in DHSs were modestly overrepresented among SNPs with significant interaction effects for intoxication frequency.

CONCLUSIONS

These findings highlight the potential utility of integrating functional genomic annotation information to increase the signal-to-noise ratio in polygenic scores and identify genetic variants that may be most susceptible to environmental modification.