Limited psychological and social effects of lifetime cannabis use frequency: Evidence from a 30-year community study of 4,078 twins

BACKGROUND

Cannabis use is associated with outcomes like income, legal problems, and psychopathology. This finding rests largely on correlational research designs, which rely at best on statistical controls for confounding. Here, we control for unmeasured confounders using a longitudinal study of twins.

METHOD

In a sample of 4,078 American adult twins first assessed decades ago, we used cotwin control mixed effects models to evaluate the effect of lifetime average frequency of cannabis consumption measured on substance use, psychiatric, and psychosocial outcomes.

RESULTS

On average, participants had a lifetime cannabis frequency of about one to two times per month, across adolescence and adulthood. As expected, in individual-level analyses, cannabis use was significantly associated with almost all outcomes in the expected directions. However, when comparing each twin to their cotwin, which inherently controls for shared genes and environments, we observed within-pair differences consistent with possible causality in three of the 22 assessed outcomes: cannabis use disorder symptoms (βW-Pooled = .15, SE = .02, p = 1.7 × 10-22), frequency of tobacco use (βW-Pooled = .06, SE = .01, p = 1.2 × 10-5), and illicit drug involvement (βW-Pooled = .06, SE = .02, p = 1.2 × 10-4). Covariate specification curve analyses indicated that within-pair effects on tobacco and illicit drug use, but not cannabis use disorder, attenuated substantially when covarying for lifetime alcohol and tobacco use.

CONCLUSIONS

The cotwin control results suggest that more frequent cannabis use causes small increases in cannabis use disorder symptoms, approximately 1.3 symptoms when going from a once-a-year use to daily use. For other outcomes, our results are more consistent with familial confounding, at least in this community population of twins. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Addendum to "Evaluating substance use outcomes of recreational cannabis legalization using a unique co-twin control design"

An earlier version of this article was published in error. Our prior publication was missing reference to a prior study on this topic. Our prior research has not found an association between recreational cannabis legalization (RCL) and negative psychosocial and psychiatric outcomes. We reported significant associations between RCL with greater cannabis frequency and fewer alcohol use disorder symptoms. The current study expands on our previous research by using a cross-sectional design and different measures of problems from cannabis and alcohol use and including additional substance use variables. The current study found similar results to our previous research.

Evaluating substance use outcomes of recreational cannabis legalization using a unique co-twin control design

Background: As more states pass recreational cannabis legalization (RCL), we must understand how RCL affects substance use.Objectives: The current study aims to examine the effect of RCL on lifetime and past-year use of cannabis, alcohol, tobacco, and other drugs, frequency of cannabis, alcohol, and tobacco use, co-use of cannabis with alcohol and tobacco, and consequences from cannabis and alcohol use.Methods: We used a unique, co-twin control design of twin pairs who were discordant for living in a state with RCL between 2018 and 2021. The sample consisted of 3,830 adult twins (41% male), including 232 twin pairs discordant for RCL. Problems from alcohol and cannabis use were assessed via the Brief Marijuana Consequences Questionnaire and the Brief Young Adult Alcohol Consequences Questionnaire.Results: Results indicated that the twin living in an RCL state was more likely to endorse past-year cannabis use (OR = 1.56, p = .009), greater number of cannabis use days in the past 6 months (β = 0.47, p = .019), but not more negative consequences from cannabis use (β = 0.21, p = .456) compared to their co-twin in a non-RCL state. There were no differences within-twin pairs in frequency of alcohol use (β=-0.05, p = .601), but the RCL twin reported fewer negative consequences from alcohol use (β=-0.29, p = .016) compared to their co-twin in a non-RCL state. We did not observe any other differences within-twin pairs on other outcomes.Conclusion: These results suggest that living in an RCL state is associated with greater cannabis frequency but not more negative consequences from cannabis use than living in a non-RCL state.

Subjective effects as predictors of substance use disorders in a clinical sample: A longitudinal study

BACKGROUND

The literature on the association between subjective effects (SEs; i.e., how an individual perceives their physiological and psychological reactions to a drug) and substance use disorders (SUDs) is largely limited to community samples. The present study addressed the following aims in a clinical sample: whether SEs predict general versus substance-specific SUD in adolescence and adulthood after controlling for conduct disorder symptoms (CDsymp); whether SEs predict SUDs across drug classes; whether SEs predict change in SUD from adolescence to adulthood; and whether there are racial/ethnic differences in associations.

METHODS

Longitudinal analyses were conducted using data from a sample of 744 clinical probands recruited from residential and outpatient SUD treatment facilities in CO during adolescence (Mage = 16.26) and re-assessed twice in adulthood (Mages = 22.56 and 28.96), approximately seven and twelve years after first assessment. SEs and CDsymp were assessed in adolescence. SUD severity was assessed at adolescence and twice during adulthood.

RESULTS

SEs assessed in adolescence robustly predicted general SUD for legal and illegal substances in adolescence and adulthood, whereas CDsymp predicted SUD primarily in adolescence. Higher positive and negative SEs in adolescence were associated with greater SUD severity after controlling for CDsymp, with similar magnitudes. Results indicated cross-substance effects of SEs on SUD. We found no evidence for racial/ethnic differences in associations.

CONCLUSIONS

We investigated the progression of SUD in a high-risk sample with greater odds of sustained SUD. In contrast to CDsymp, both positive and negative SEs consistently predicted general SUD across substances in adolescence and adulthood.

Recreational cannabis legalization has had limited effects on a wide range of adult psychiatric and psychosocial outcomes

BACKGROUND

The causal impacts of recreational cannabis legalization are not well understood due to the number of potential confounds. We sought to quantify possible causal effects of recreational cannabis legalization on substance use, substance use disorder, and psychosocial functioning, and whether vulnerable individuals are more susceptible to the effects of cannabis legalization than others.

METHODS

We used a longitudinal, co-twin control design in 4043 twins (N = 240 pairs discordant on residence), first assessed in adolescence and now age 24-49, currently residing in states with different cannabis policies (40% resided in a recreationally legal state). We tested the effect of legalization on outcomes of interest and whether legalization interacts with established vulnerability factors (age, sex, or externalizing psychopathology).

RESULTS

In the co-twin control design accounting for earlier cannabis frequency and alcohol use disorder (AUD) symptoms respectively, the twin living in a recreational state used cannabis on average more often (βw = 0.11, p = 1.3 × 10-3), and had fewer AUD symptoms (βw = -0.11, p = 6.7 × 10-3) than their co-twin living in an non-recreational state. Cannabis legalization was associated with no other adverse outcome in the co-twin design, including cannabis use disorder. No risk factor significantly interacted with legalization status to predict any outcome.

CONCLUSIONS

Recreational legalization was associated with increased cannabis use and decreased AUD symptoms but was not associated with other maladaptations. These effects were maintained within twin pairs discordant for residence. Moreover, vulnerabilities to cannabis use were not exacerbated by the legal cannabis environment. Future research may investigate causal links between cannabis consumption and outcomes.

Impacts of recreational cannabis legalization on cannabis use: a longitudinal discordant twin study

AIMS

To estimate the effect of recreational legalization on cannabis use frequency and sources of variance across legal environments.

DESIGN

Longitudinal discordant twin and gene-environment interaction models in twins recruited from birth records and assessed prospectively.

SETTING

The United States, including states with different recreational cannabis policies before and after 2014, when recreational cannabis was first legalized.

PARTICIPANTS

Two longitudinal, prospectively assessed samples of American twins aged 24-47 (n = 1425 in legal states, n = 1996 in illegal states), including 111 monozygotic pairs discordant for residence.

MEASUREMENTS

Current cannabis use frequency (measured continuously and ordinally) was the primary outcome, and the predictor was recreational status of cannabis (legal/illegal) in the participant's state of residence at the time of assessment. Covariates include age, sex and cannabis use frequency prior to 2014.

FINDINGS

Accounting for pre-2014 use, residents of legal states used cannabis more frequently than residents of illegal states (b = 0.21, P = 8.08 × 10-5 ). Comparing 111 pairs of monozygotic twins discordant for residence confirmed the effect (b = 0.18, P = 0.014). There was inconclusive evidence for genetic influences on cannabis use frequency that were specific to the legal environment [χ2  = 2.9 × 10-9 , degrees of freedom (d.f.) = 1, P > 0.999]. Existing genetic influences were moderated by the legal environment, as the genetic correlation between marijuana use before and after legalization was lower in states that legalized (rgenetic  = 0.24) compared with states that did not (rgenetic  = 0.78, Pdifference  = 0.016).

CONCLUSIONS

In the United States, there appears to be a ~ 20% average increase in cannabis use frequency attributable to recreational legalization, consistent across increasingly rigorous designs. In addition, the heritability of cannabis use frequency appears to be moderated by legalization.

The effects of cannabis use on physical health: A co-twin control study

BACKGROUND

Research on the influence of cannabis use on anthropometrics, cardiovascular and pulmonary function, and other indicators of physical health has reported mixed results. We examined whether cannabis frequency is associated with physical health outcomes phenotypically and after controlling for shared genetic and environmental factors via a longitudinal co-twin control design.

METHODS

We tested the phenotypic associations of adolescent, young adult, and adult cannabis frequency with adult physical health. Next, we ran multilevel models to test if significant phenotypic associations remained at the between-family and within-twin pair levels. Participants include 677 individual twins (308 twin pairs) aged 25-35.

RESULTS

At the phenotypic level, adolescent cannabis use was associated with less adult exercise engagement (b = - 0.846 min, p = .000). Adult cannabis use was associated with a lower resting heart rate (HR; b = - 0.170 bpm, p = .001) and more frequent appetite loss (b = 0.018, p = .000). Only between-family effects were significant for adolescent cannabis use and exercise engagement (b = - 1.147 min, p = .000) and adult cannabis use and appetite loss frequency (b = 0.041, p = .002). The total within-twin (b = - 0.184, p = .014), MZ only (b = - 0.304, p = .003), and between-family effects (b = - 0.164, p = .025) were significant between adult cannabis use and a lower resting HR, which persisted after controlling for familial confounds and other substance use.

CONCLUSIONS

The associations between cannabis use with exercise engagement and frequency of appetite loss are explained by familial confounding while the association between cannabis use and resting HR was not. These results do not support a causal association between cannabis use once a week and poorer physical health effects among adults aged 25-35.

Executive functions as a mediator of childhood maltreatment on adult psychopathology: A longitudinal mediation analysis comparing maltreatment factor models

BACKGROUND

Childhood maltreatment (CM), executive functions (EFs), and psychiatric disorders all correlate highly. Changes in EFs during adolescence related to CM present a possible mediating mechanism for the development of psychiatric disorders, yet no study has analyzed this longitudinally while comparing predictive capacity of different CM factor structures. We hypothesized that changes in EFs from adolescence to adulthood would mediate, in part, associations between CM, internalizing disorders (INT), and anti-social personality disorder (ASPD) while different subtypes of CM would differentially predict INT and ASPD.

OBJECTIVE

This study longitudinally examined the mediating effects of EFs on associations between CM, INT, and ASPD while comparing prediction of two CM factor structures.

PARTICIPANTS

High-risk subjects selected for drug use in adolescence (N = 658) from mean ages 16 to 23.

METHODS

A Bayesian structural equation model was deployed to analyze change in EFs as a mediator of the relationship between CM and adult INT and ASPD. CM was measured using two factor structures: a single overall factor and four correlated factors representing CM subtypes.

RESULTS

CM significantly predicted INT and ASPD but there was no evidence that the relationship was substantially mediated through EFs. High correlations among subtypes of CM limited the unique predictions of each subtype on INT and ASPD.

CONCLUSION

In this high-risk sample, the collinearity of CM subtypes obscured their predictions of outcome measures supporting the use of one CM factor. EFs did not significantly mediate associations between CM and psychiatric disorders, but further research on these relationships is warranted.

Familial factors may not explain the effect of moderate-to-heavy cannabis use on cognitive functioning in adolescents: a sibling-comparison study

AIMS

To examine whether moderate adolescent cannabis use has neurocognitive effects that are unexplained by familial confounds, which prior family-controlled studies may not have identified.

DESIGN

A quasi-experimental, sibling-comparison design was applied to a prospective, observational study of adolescents with moderate cannabis use. Participants were recruited from 2001 to 2006 (mean age = 17 years). A second wave of data was collected from 2008 to 2013 (mean age = 24 years).

SETTING

Two US metropolitan communities.

PARTICIPANTS

A total of 1192 adolescents from 596 families participated in this study. Participants were primarily male (64%) and racially and ethnically diverse (non-Hispanic white = 45%). A sibling in each family was a clinical proband identified due to delinquent behaviors. Whereas prior family-controlled studies have used samples of primarily infrequent cannabis users (mean = 1-2 days/month), participants here endorsed levels of cannabis use comparable to findings from epidemiological cohort studies (mean = 7-9 days/month).

MEASUREMENTS

Semi-structured clinical interviews assessed drug use, and a neuropsychological battery assessed cognitive abilities. Covariates included age at assessment, gender and alcohol use.

FINDINGS

After correcting for multiple testing, a greater frequency and earlier onset of regular cannabis use were associated with poorer cognitive performance, specifically on tests of verbal memory. Further, after accounting for familial factors shared by siblings and alcohol use, poorer verbal memory performance was still associated with greater life-time frequency of cannabis use at wave 1 [b = -0.007 (-0.002, -0.012), adjusted P = 0.036]; earlier cannabis use at wave 2 [b = -0.12 (-0.05, -0.19), adjusted P = 0.006; b = -0.14 (-0.06, -0.23), adjusted P = 0.006]; and greater frequency of past 6 months use at wave 2 [b = -0.02 (-0.01, -0.03), adjusted P = 0.002; b = -0.02 (-0.01, -0.03), adjusted P = 0.008].

CONCLUSIONS

Moderate adolescent cannabis use may have adverse effects on cognitive functioning, specifically verbal memory, that cannot be explained by familial factors.

Sleep deficits and cannabis use behaviors: an analysis of shared genetics using linkage disequilibrium score regression and polygenic risk prediction

STUDY OBJECTIVES

Estimate the genetic relationship of cannabis use with sleep deficits and an eveningness chronotype.

METHODS

We used linkage disequilibrium score regression (LDSC) to analyze genetic correlations between sleep deficits and cannabis use behaviors. Secondly, we generated sleep deficit polygenic risk score (PRS) and estimated their ability to predict cannabis use behaviors using linear and logistic regression. Summary statistics came from existing genome-wide association studies of European ancestry that were focused on sleep duration, insomnia, chronotype, lifetime cannabis use, and cannabis use disorder (CUD). A target sample for PRS prediction consisted of high-risk participants and participants from twin/family community-based studies (European ancestry; n = 760, male = 64%; mean age = 26.78 years). Target data consisted of self-reported sleep (sleep duration, feeling tired, and taking naps) and cannabis use behaviors (lifetime ever use, number of lifetime uses, past 180-day use, age of first use, and lifetime CUD symptoms).

RESULTS

Significant genetic correlation between lifetime cannabis use and an eveningness chronotype (rG = 0.24, p < 0.001), as well as between CUD and both short sleep duration (<7 h; rG = 0.23, p = 0.017) and insomnia (rG = 0.20, p = 0.020). Insomnia PRS predicted earlier age of first cannabis use (OR = 0.92, p = 0.036) and increased lifetime CUD symptom count (OR = 1.09, p = 0.012).

CONCLUSION

Cannabis use is genetically associated with both sleep deficits and an eveningness chronotype, suggesting that there are genes that predispose individuals to both cannabis use and sleep deficits.

A large-scale genome-wide association study meta-analysis of cannabis use disorder

BACKGROUND

Variation in liability to cannabis use disorder has a strong genetic component (estimated twin and family heritability about 50-70%) and is associated with negative outcomes, including increased risk of psychopathology. The aim of the study was to conduct a large genome-wide association study (GWAS) to identify novel genetic variants associated with cannabis use disorder.

METHODS

To conduct this GWAS meta-analysis of cannabis use disorder and identify associations with genetic loci, we used samples from the Psychiatric Genomics Consortium Substance Use Disorders working group, iPSYCH, and deCODE (20 916 case samples, 363 116 control samples in total), contrasting cannabis use disorder cases with controls. To examine the genetic overlap between cannabis use disorder and 22 traits of interest (chosen because of previously published phenotypic correlations [eg, psychiatric disorders] or hypothesised associations [eg, chronotype] with cannabis use disorder), we used linkage disequilibrium score regression to calculate genetic correlations.

FINDINGS

We identified two genome-wide significant loci: a novel chromosome 7 locus (FOXP2, lead single-nucleotide polymorphism [SNP] rs7783012; odds ratio [OR] 1·11, 95% CI 1·07-1·15, p=1·84 × 10-9) and the previously identified chromosome 8 locus (near CHRNA2 and EPHX2, lead SNP rs4732724; OR 0·89, 95% CI 0·86-0·93, p=6·46 × 10-9). Cannabis use disorder and cannabis use were genetically correlated (rg 0·50, p=1·50 × 10-21), but they showed significantly different genetic correlations with 12 of the 22 traits we tested, suggesting at least partially different genetic underpinnings of cannabis use and cannabis use disorder. Cannabis use disorder was positively genetically correlated with other psychopathology, including ADHD, major depression, and schizophrenia.

INTERPRETATION

These findings support the theory that cannabis use disorder has shared genetic liability with other psychopathology, and there is a distinction between genetic liability to cannabis use and cannabis use disorder.

FUNDING

National Institute of Mental Health; National Institute on Alcohol Abuse and Alcoholism; National Institute on Drug Abuse; Center for Genomics and Personalized Medicine and the Centre for Integrative Sequencing; The European Commission, Horizon 2020; National Institute of Child Health and Human Development; Health Research Council of New Zealand; National Institute on Aging; Wellcome Trust Case Control Consortium; UK Research and Innovation Medical Research Council (UKRI MRC); The Brain & Behavior Research Foundation; National Institute on Deafness and Other Communication Disorders; Substance Abuse and Mental Health Services Administration (SAMHSA); National Institute of Biomedical Imaging and Bioengineering; National Health and Medical Research Council (NHMRC) Australia; Tobacco-Related Disease Research Program of the University of California; Families for Borderline Personality Disorder Research (Beth and Rob Elliott) 2018 NARSAD Young Investigator Grant; The National Child Health Research Foundation (Cure Kids); The Canterbury Medical Research Foundation; The New Zealand Lottery Grants Board; The University of Otago; The Carney Centre for Pharmacogenomics; The James Hume Bequest Fund; National Institutes of Health: Genes, Environment and Health Initiative; National Institutes of Health; National Cancer Institute; The William T Grant Foundation; Australian Research Council; The Virginia Tobacco Settlement Foundation; The VISN 1 and VISN 4 Mental Illness Research, Education, and Clinical Centers of the US Department of Veterans Affairs; The 5th Framework Programme (FP-5) GenomEUtwin Project; The Lundbeck Foundation; NIH-funded Shared Instrumentation Grant S10RR025141; Clinical Translational Sciences Award grants; National Institute of Neurological Disorders and Stroke; National Heart, Lung, and Blood Institute; National Institute of General Medical Sciences.

Leveraging genome-wide data to investigate differences between opioid use vs. opioid dependence in 41,176 individuals from the Psychiatric Genomics Consortium

To provide insights into the biology of opioid dependence (OD) and opioid use (i.e., exposure, OE), we completed a genome-wide analysis comparing 4503 OD cases, 4173 opioid-exposed controls, and 32,500 opioid-unexposed controls, including participants of European and African descent (EUR and AFR, respectively). Among the variants identified, rs9291211 was associated with OE (exposed vs. unexposed controls; EUR z = -5.39, p = 7.2 × 10-8). This variant regulates the transcriptomic profiles of SLC30A9 and BEND4 in multiple brain tissues and was previously associated with depression, alcohol consumption, and neuroticism. A phenome-wide scan of rs9291211 in the UK Biobank (N > 360,000) found association of this variant with propensity to use dietary supplements (p = 1.68 × 10-8). With respect to the same OE phenotype in the gene-based analysis, we identified SDCCAG8 (EUR + AFR z = 4.69, p = 10-6), which was previously associated with educational attainment, risk-taking behaviors, and schizophrenia. In addition, rs201123820 showed a genome-wide significant difference between OD cases and unexposed controls (AFR z = 5.55, p = 2.9 × 10-8) and a significant association with musculoskeletal disorders in the UK Biobank (p = 4.88 × 10-7). A polygenic risk score (PRS) based on a GWAS of risk-tolerance (n = 466,571) was positively associated with OD (OD vs. unexposed controls, p = 8.1 × 10-5; OD cases vs. exposed controls, p = 0.054) and OE (exposed vs. unexposed controls, p = 3.6 × 10-5). A PRS based on a GWAS of neuroticism (n = 390,278) was positively associated with OD (OD vs. unexposed controls, p = 3.2 × 10-5; OD vs. exposed controls, p = 0.002) but not with OE (p = 0.67). Our analyses highlight the difference between dependence and exposure and the importance of considering the definition of controls in studies of addiction.

Association studies of up to 1.2 million individuals yield new insights into the genetic etiology of tobacco and alcohol use

Tobacco and alcohol use are leading causes of mortality that influence risk for many complex diseases and disorders1. They are heritable2,3 and etiologically related4,5 behaviors that have been resistant to gene discovery efforts6-11. In sample sizes up to 1.2 million individuals, we discovered 566 genetic variants in 406 loci associated with multiple stages of tobacco use (initiation, cessation, and heaviness) as well as alcohol use, with 150 loci evidencing pleiotropic association. Smoking phenotypes were positively genetically correlated with many health conditions, whereas alcohol use was negatively correlated with these conditions, such that increased genetic risk for alcohol use is associated with lower disease risk. We report evidence for the involvement of many systems in tobacco and alcohol use, including genes involved in nicotinic, dopaminergic, and glutamatergic neurotransmission. The results provide a solid starting point to evaluate the effects of these loci in model organisms and more precise substance use measures.

Transancestral GWAS of alcohol dependence reveals common genetic underpinnings with psychiatric disorders

Liability to alcohol dependence (AD) is heritable, but little is known about its complex polygenic architecture or its genetic relationship with other disorders. To discover loci associated with AD and characterize the relationship between AD and other psychiatric and behavioral outcomes, we carried out the largest genome-wide association study to date of DSM-IV-diagnosed AD. Genome-wide data on 14,904 individuals with AD and 37,944 controls from 28 case-control and family-based studies were meta-analyzed, stratified by genetic ancestry (European, n = 46,568; African, n = 6,280). Independent, genome-wide significant effects of different ADH1B variants were identified in European (rs1229984; P = 9.8 × 10-13) and African ancestries (rs2066702; P = 2.2 × 10-9). Significant genetic correlations were observed with 17 phenotypes, including schizophrenia, attention deficit-hyperactivity disorder, depression, and use of cigarettes and cannabis. The genetic underpinnings of AD only partially overlap with those for alcohol consumption, underscoring the genetic distinction between pathological and nonpathological drinking behaviors.

Predictors of adult outcomes in clinically- and legally-ascertained youth with externalizing problems

Externalizing problems (EP), including rule-breaking, aggression, and criminal involvement, are highly prevalent during adolescence, but the adult outcomes of adolescents exhibiting EP are characterized by heterogeneity. Although many youths' EP subside after adolescence, others' persists into adulthood. Characterizing the development of severe EP is essential to prevention and intervention efforts. Multiple predictors of adult antisocial personality disorder (ASPD) and legal outcomes of a large sample (N = 1205) of clinically- or legally-ascertained adolescents (ages 12-19 years) with severe EP were examined. Many psychosocial predictors hypothesized to predict persistence of EP demonstrated zero-order associations with adult outcomes, but accounted for little unique variation after accounting for baseline conduct disorder symptoms (CD) and demographic factors. Baseline measures of intelligence, which explained independent variation in legal outcomes, provided the only consistent exception to this pattern, though future work is needed to parse these effects from those of socioeconomic factors. CD severity during adolescence is a parsimonious index of liability for persistence of EP into adulthood that explains outcome variance above and beyond all other demographic and psychosocial predictors in this sample.

Independent predictors of mortality in adolescents ascertained for conduct disorder and substance use problems, their siblings and community controls

BACKGROUND AND AIMS

Adolescents with conduct and substance use problems are at increased risk for premature mortality, but the extent to which these risk factors reflect family- or individual-level differences and account for shared or unique variance is unknown. This study examined common and independent contributions to mortality hazard in adolescents ascertained for conduct disorder (CD) and substance use disorder (SUD), their siblings and community controls, hypothesizing that individual differences in CD and SUD severity would explain unique variation in mortality risk beyond that due to clinical/control status and demographic factors.

DESIGN

Mortality analysis in a prospective study (Genetics of Antisocial Drug Dependence Study) that began in 1993.

SETTING

Multi-site sample recruited in San Diego, California and Denver, Colorado, USA.

PARTICIPANTS

A total of 1463 clinical probands were recruited through the juvenile correctional system, court-mandated substance abuse treatment programs and correctional schools, along with 1399 of their siblings, and 904 controls.

MEASUREMENTS

Mortality and cause-of-death were assessed via National Death Index search (released October, 2017).

FINDINGS

There were 104 deaths documented among 3766 (1168 female) adolescents and young adults (average age 16.79 years at assessment, 32.69 years at death/censoring). Mortality hazard for clinical probands and their siblings was 4.99 times greater than that of controls (95% confidence interval = 2.40-10.40; P < 0.001). After accounting for demographic characteristics, site, clinical status, familial dependence and shared contributions of CD and SUD, CD independently predicted mortality hazard, whereas SUD severity did not.

CONCLUSIONS

In the United States, youth with conduct and substance use disorders and their siblings face far greater risk of premature death than demographically similar community controls. In contrast to substance use disorder severity, conduct disorder is a robust predictor of unique variance in all-cause mortality hazard beyond other risk factors.

Genome-wide association meta-analysis of age at first cannabis use

BACKGROUND AND AIMS

Cannabis is one of the most commonly used substances among adolescents and young adults. Earlier age at cannabis initiation is linked to adverse life outcomes, including multi-substance use and dependence. This study estimated the heritability of age at first cannabis use and identified associations with genetic variants.

METHODS

A twin-based heritability analysis using 8055 twins from three cohorts was performed. We then carried out a genome-wide association meta-analysis of age at first cannabis use in a discovery sample of 24 953 individuals from nine European, North American and Australian cohorts, and a replication sample of 3735 individuals.

RESULTS

The twin-based heritability for age at first cannabis use was 38% [95% confidence interval (CI) = 19-60%]. Shared and unique environmental factors explained 39% (95% CI = 20-56%) and 22% (95% CI = 16-29%). The genome-wide association meta-analysis identified five single nucleotide polymorphisms (SNPs) on chromosome 16 within the calcium-transporting ATPase gene (ATP2C2) at P < 5E-08. All five SNPs are in high linkage disequilibrium (LD) (r2  > 0.8), with the strongest association at the intronic variant rs1574587 (P = 4.09E-09). Gene-based tests of association identified the ATP2C2 gene on 16q24.1 (P = 1.33e-06). Although the five SNPs and ATP2C2 did not replicate, ATP2C2 has been associated with cocaine dependence in a previous study. ATP2B2, which is a member of the same calcium signalling pathway, has been associated previously with opioid dependence. SNP-based heritability for age at first cannabis use was non-significant.

CONCLUSION

Age at cannabis initiation appears to be moderately heritable in western countries, and individual differences in onset can be explained by separate but correlated genetic liabilities. The significant association between age of initiation and ATP2C2 is consistent with the role of calcium signalling mechanisms in substance use disorders.

Positive expectancies mediate the association between sensation seeking and marijuana outcomes in at-risk young adults: A test of the acquired preparedness model

BACKGROUND AND OBJECTIVES

The acquired preparedness model (APM) integrates personality trait research and psychosocial learning, which are theorized to ultimately increase risk for problematic substance use outcomes.

METHODS

The present study uses the APM to examine the potential mediational role of positive and negative expectancies on the relationship between impulsivity and two marijuana outcomes (ie, frequency of use and marijuana use disorder [MUD] symptom count) among an at-risk sample of young adults with history of antisocial behavior and substance use in adolescence and their siblings (n = 312).

RESULTS

Results suggest a significant indirect effect of sensation seeking on recent marijuana use through positive marijuana expectancies. There also was a significant indirect effect of sensation seeking on past-year MUD symptoms through positive expectancies. No significant indirect effects through negative expectancies were found for either outcome.

DISCUSSION AND CONCLUSIONS

Our findings are consistent with the APM and suggest that higher sensation seeking is related to increased positive beliefs about marijuana outcomes, which is related to higher marijuana use and more MUD symptoms.

SCIENTIFIC SIGNIFICANCE

These findings suggest that positive expectancies are an important risk factor for marijuana use and misuse, particularly for at-risk individuals with elevated rates of sensation seeking. Positive marijuana expectancies may be important to address in interventions for at-risk individuals. (Am J Addict 2018;XX:1-6).

Long-term opioid use after inpatient surgery - A retrospective cohort study

BACKGROUND

Knowledge of incidence and risk factors for long-term opioid prescribing is critical for surgical patients. In this retrospective cohort study, we linked information available at the time of surgery with prescription data to ascertain characteristics associated with prolonged opioid therapy.

METHODS

Patients (n = 6003) with claims in the Colorado All Payer Claims Database (APCD) were matched with 20,501 encounters in a clinical database. Rates of prescription filling were defined by at least one monthly opioid claim relative to the date of surgery. Associations of variables with claims during months 2-6 post-operatively ("long-term prescription filling") were evaluated, and significant variables were jointly modeled using binomial regression.

RESULTS

Rates of patients filling opioid prescriptions preoperatively [month (M) relative to date of surgery] were 22%(-3 M), 24%(-2 M), and 27%(-1 M); after surgery, opioid fill rates were 62%(1 M), 28%(2 M), 24%(3), 24%(4 M), 23%(5 M), and 22%(6 M). The majority, 71-76%, of patients filling prescriptions in months 2-6 after surgery had also filled before surgery. In the binomial regression model, long-term opioid use was associated with prior opioid use (p < 0.0001), age ≥26 to <65 relative to age ≥ 65 (p < 0.0001), orthopedic surgery (p = 0.001), colorectal surgery (p = 0.003), multiple procedures (p < 0.0001), and worse physical status classification (p < 0.0001).

CONCLUSIONS

Patients who had filled opioid prescriptions preoperatively comprised the majority of the group who filled long-term prescriptions. Surgical procedures were associated with discontinuation of previous opioid prescribing in some patients. For others, surgery marked the initiation of prolonged opioid therapy. Surgical encounters should include interventions aimed to reduce long-term opioid use.

Impulsivity Dimensions and Risky Sex Behaviors in an At-Risk Young Adult Sample

Impulsivity is a personality-based risk factor that has been well studied in relation to risky sexual behavior. Recent conceptualizations of impulsivity have proposed multidimensional facets comprised of premeditation, perseverance, sensation seeking, negative urgency, and positive urgency (UPPS-P model). Prior studies have found that these facets are associated with risky sexual behavior in adolescent and college student samples, but no prior studies have evaluated them in clinical samples. The current study examined how impulsivity-related traits related to two different risky sexual behaviors in a clinical sample of at-risk young adults who had both conduct disorder and substance use disorder symptoms as adolescents (n = 529). Lack of premeditation was also tested as a moderator of the relationship between facets of impulsivity and both risky sex outcomes. Results demonstrated that sensation seeking, negative urgency, and positive urgency were correlated with risky sex behaviors. Additionally, multiple regression analyses indicated that sensation seeking was uniquely associated with the number of sexual partners in the past 5 years, whereas positive urgency was uniquely associated with unprotected sex while under the influence. Finally, a significant interaction between lack of premeditation and negative urgency suggests that at-risk young adults with both high negative urgency and lack of premeditation were the likeliest to have the most sexual partners in the past 5 years. This study adds to the current understanding of the relationship between reward- and affect-driven facets of impulsivity and risky sexual behaviors and may lend utility to the development of interventions for at-risk populations.

Cannabis use disorder and male sex predict medical cannabis card status in a sample of high risk adolescents

OBJECTIVE

To examine if a substance use disorder (SUD), especially cannabis use disorder in adolescence, predicts future medical cannabis card status among high-risk youth.

METHODS

Data collection occurred in Denver and San Diego. We recruited adolescents, with or at high risk for SUD and conduct problems (hereafter probands) and their siblings (n=654). Baseline (Wave 1) assessments took place between 1999 and 2008, and follow-up (Wave 2) took place between 2010 and 2013. In initial bivariate analyses, we examined whether baseline DSM-IV cannabis abuse/dependence (along with other potential predictors) was associated with possessing a medical cannabis card in young adulthood (Wave 2). Significant predictors were then included in a multiple binomial regression. Self-reported general physical health was also evaluated at both time points. Finally, within Wave 2, we tested whether card status was associated with concurrent substance dependence.

RESULTS

About 16% of the sample self-reported having a medical cannabis card at follow-up. Though bivariate analyses demonstrated that multiple predictors were significantly associated with Wave 2 card status, in our multiple binomial regression only cannabis abuse/dependence and male sex remained significant. At Wave 2, those with a medical cannabis card were significantly more likely to endorse criteria for concurrent cannabis dependence. There was no significant difference in self-reported general physical health.

CONCLUSIONS

Cannabis abuse/dependence and male sex positively predicted future medical cannabis card holder status among a sample of high risk adolescents. Physicians conducting evaluations for medical cannabis cards should carefully evaluate and consider past and concurrent cannabis addiction.

Unique and interactive effects of impulsivity facets on reckless driving and driving under the influence in a high-risk young adult sample

Risky driving behaviors are disproportionately high among young adults and impulsivity is a robust risk factor. Recent conceptualizations have proposed multidimensional facets of impulsivity comprised of negative urgency, premeditation, perseverance, sensation seeking, and positive urgency (UPPS-P model). Prior studies have found these facets are associated with risky driving behaviors in college student samples, but no prior studies have examined these facets in clinical samples. This study examined the unique and interactive effects of UPPS-P impulsivity facets on past-year risky driving behaviors in a sample of high-risk young adults (ages 18-30 years) with a history of substance use and antisocial behavior and their siblings (n=1,100). Multilevel Poisson regressions indicated that sensation seeking and negative urgency were uniquely and positively associated with both frequency of past-year reckless driving and driving under the influence. Moreover, lack of premeditation was uniquely and positively associated with reckless driving, whereas lack of perseverance was uniquely and positively associated with driving under the influence. Furthermore, lack of premeditation moderated and strengthened the positive association between sensation seeking and driving under the influence. These study findings suggest that assessing multiple facets of trait impulsivity could facilitate targeted prevention efforts among young adults with a history of externalizing psychopathology.

Risky driving and sexual behaviors as developmental outcomes of co-occurring substance use and antisocial behavior

PURPOSE

To examine the associations between substance use and antisocial behavior trajectories and seven risky behaviors over time.

METHOD

Data were collected from a high-risk sample of adolescents followed into young adulthood. Five trajectory classes, identified based on dual development of substance use and antisocial behavior symptoms, were used to predict three risky driving and four risky sexual behaviors.

RESULTS

In this high-risk sample (n=530), participants reported notably high overall rates of reckless driving (55.5%) and unprotected sex under the influence (44.8%) in the past year. Risky behaviors that are typically of low base rates in population-based studies were also elevated, with 8.8% reporting past-year driving under the influence (DUI) charge, 17.6% reporting lifetime sexually transmitted infection (STI), and 10.4% reporting lifetime injection drug use. The Dual Chronic class had the highest levels of all seven risky behaviors, and were 3-4 times more likely to report risky driving, lifetime STI, and injection drug use than the Relatively Resolved class. Rates of past-year reckless driving and DUI were elevated among classes with persistent antisocial behavior, whereas rates of DUI, DUI charge, and unprotected sex under the influence were elevated among classes with persistent substance use.

CONCLUSIONS

Young adults with persistent co-occurring substance use and antisocial behavior engage in multiple very costly risky behaviors. Differential associations between risky behaviors and trajectory classes highlight the need for targeted interventions.

Test for association of common variants in GRM7 with alcohol consumption

Recent work using a mouse model has identified the glutamate metabotropic receptor 7 (Grm7) gene as a strong candidate gene for alcohol consumption. Although there has been some work examining the effect of human glutamate metabotropic receptor 7 (GRM7) polymorphisms on human substance use disorders, the majority of the work has focused on other psychiatric disorders such as ADHD, major depressive disorder, schizophrenia, bipolar disorder, panic disorder, and autism spectrum disorders. The current study aimed to evaluate evidence for association between GRM7 and alcohol behaviors in humans using a single nucleotide polymorphism (SNP) approach, as well as a gene-based approach. Using 1803 non-Hispanic European Americans (EAs) (source: the Colorado Center on Antisocial Drug Dependence [CADD]) and 1049 EA subjects from an independent replication sample (source: the Genetics of Antisocial Drug Dependence [GADD]), two SNPs in GRM7 were examined for possible association with alcohol consumption using two family-based association tests implemented in FBAT and QTDT. Rs3749380 was suggestively associated with alcohol consumption in the CADD sample (p = 0.010) with the minor T allele conferring risk. There was no evidence for association in the GADD sample. A gene-based test using four Genome-Wide Association Studies (GWAS) revealed no association between variation in GRM7 and alcohol consumption. This study had several limitations: the SNPs chosen likely do not tag expression quantitative trait loci; a human alcohol consumption phenotype was used, complicating the interpretation with respect to rodent studies that found evidence for a cis-regulatory link between alcohol preference and Grm7; and only common SNPs imputed in all four datasets were included in the gene-based test. These limitations highlight the fact that rare variants, some potentially important common signals in the gene, and regions farther upstream were not examined.

Adolescent Male Conduct-Disordered Patients in Substance Use Disorder Treatment: Examining the "Limited Prosocial Emotions" Specifier

To our knowledge, this is the first study to examine the DSM-5-defined conduct disorder (CD) with limited prosocial emotions (LPE) among adolescents in substance use disorder (SUD) treatment, despite the high rates of CD in this population. We tested previously published methods of LPE categorization in a sample of male conduct-disordered patients in SUD treatment (n=196). CD with LPE patients did not demonstrate a distinct pattern in terms of demographics or co-morbidity regardless of the categorization method utilized. In conclusion, LPE, as operationalized here, does not identify a distinct subgroup of patients based on psychiatric comorbidity, SUD diagnoses, or demographics.

Effect of adolescent substance use and antisocial behavior on the development of early adulthood depression

Major depressive disorder (MDD) is a prevalent and frequently comorbid psychiatric disorder. This study evaluates the development of depressive symptoms, MDD diagnosis, and suicidal ideation in a high-risk sample (N=524) diagnosed with conduct disorder (CD) and substance use disorder (SUD) symptoms as youth and re-assessed approximately 6.5 years later. Dual trajectory classes of both alcohol and other drug use (AOD) and antisocial behavior (ASB), previously identified using latent class growth analyses (LCGA), were used to predict depression outcomes. The Dual Chronic, Increasing AOD/Persistent ASB, and Decreasing Drugs/Persistent ASB classes had higher past-week depression scores, more past-year MDD symptoms, and were more likely to have past-year MDD than the Resolved class. The Dual Chronic and Decreasing Drugs/Persistent ASB classes also had more past-year MDD symptoms than the Persistent AOD/Adolescent ASB class. Youth at highest risk for developing or maintaining depression in adulthood had the common characteristic of persistent antisocial behavior. This suggests young adulthood depression is associated more with persistent antisocial behavior than with persistent substance use in comorbid youth. As such, interventions targeting high-risk youth, particularly those with persistent antisocial behavior, are needed to help reduce the risk of severe psychosocial consequences (including risk for suicide) in adulthood.

Evidence for Association Between Low Frequency Variants in CHRNA6/CHRNB3 and Antisocial Drug Dependence

Common SNPs in nicotinic acetylcholine receptor genes (CHRN genes) have been associated with drug behaviors and personality traits, but the influence of rare genetic variants is not well characterized. The goal of this project was to identify novel rare variants in CHRN genes in the Center for Antisocial Drug Dependence (CADD) and Genetics of Antisocial Drug Dependence (GADD) samples and to determine if low frequency variants are associated with antisocial drug dependence. Two samples of 114 and 200 individuals were selected using a case/control design including the tails of the phenotypic distribution of antisocial drug dependence. The capture, sequencing, and analysis of all variants in 16 CHRN genes (CHRNA1-7, 9, 10, CHRNB1-4, CHRND, CHRNG, CHRNE) were performed independently for each subject in each sample. Sequencing reads were aligned to the human reference sequence using BWA prior to variant calling with the Genome Analysis ToolKit (GATK). Low frequency variants (minor allele frequency < 0.05) were analyzed using SKAT-O and C-alpha to examine the distribution of rare variants among cases and controls. In our larger sample, the region containing the CHRNA6/CHRNB3 gene cluster was significantly associated with disease status using both SKAT-O and C-alpha (unadjusted p values <0.05). More low frequency variants in the CHRNA6/CHRNB3 gene region were observed in cases compared to controls. These data support a role for genetic variants in CHRN genes and antisocial drug behaviors.

Genome-wide association study of lifetime cannabis use based on a large meta-analytic sample of 32 330 subjects from the International Cannabis Consortium

Cannabis is the most widely produced and consumed illicit psychoactive substance worldwide. Occasional cannabis use can progress to frequent use, abuse and dependence with all known adverse physical, psychological and social consequences. Individual differences in cannabis initiation are heritable (40-48%). The International Cannabis Consortium was established with the aim to identify genetic risk variants of cannabis use. We conducted a meta-analysis of genome-wide association data of 13 cohorts (N=32 330) and four replication samples (N=5627). In addition, we performed a gene-based test of association, estimated single-nucleotide polymorphism (SNP)-based heritability and explored the genetic correlation between lifetime cannabis use and cigarette use using LD score regression. No individual SNPs reached genome-wide significance. Nonetheless, gene-based tests identified four genes significantly associated with lifetime cannabis use: NCAM1, CADM2, SCOC and KCNT2. Previous studies reported associations of NCAM1 with cigarette smoking and other substance use, and those of CADM2 with body mass index, processing speed and autism disorders, which are phenotypes previously reported to be associated with cannabis use. Furthermore, we showed that, combined across the genome, all common SNPs explained 13-20% (P<0.001) of the liability of lifetime cannabis use. Finally, there was a strong genetic correlation (rg=0.83; P=1.85 × 10(-8)) between lifetime cannabis use and lifetime cigarette smoking implying that the SNP effect sizes of the two traits are highly correlated. This is the largest meta-analysis of cannabis GWA studies to date, revealing important new insights into the genetic pathways of lifetime cannabis use. Future functional studies should explore the impact of the identified genes on the biological mechanisms of cannabis use.

Depression, Stressful Life Events, and the Impact of Variation in the Serotonin Transporter: Findings from the National Longitudinal Study of Adolescent to Adult Health (Add Health)

Background

The low transcriptionally efficient short-allele of the 5HTTLPR serotonin transporter polymorphism has been implicated to moderate the relationship between the experience of stressful life events (SLEs) and depression. Despite numerous attempts at replicating this observation, results remain inconclusive.

Methods

We examined this relationship in young-adult Non-Hispanic white males and females between the ages of 22 and 26 (n = 4724) participating in the National Longitudinal Study of Adolescent to Adult Health (Add Health) with follow-up information every six years since 1995.

Results

Linear and logistic regression models, corrected for multiple testing, indicated that carriers of one or more of the S-alleles were more sensitive to stress than those with two L-alleles and at a higher risk for depression. This relationship behaved in a dose-response manner such that the risk for depression was greatest among those who reported experiencing higher numbers of SLEs. In post-hoc analyses we were not able to replicate an interaction effect for suicide ideation but did find suggestive evidence that the effects of SLEs and 5HTTLPR on suicide ideation differed for males and females. There were no effects of childhood maltreatment.

Discussion

Our results provide partial support for the original hypothesis that 5-HTTLPR genotype interacts with the experience of stressful life events in the etiology of depression during young adulthood. However, even with this large sample, and a carefully constructed a priori analysis plan, the results were still not definitive. For the purposes of replication, characterizing the 5HTTLPR in other large data sets with extensive environmental and depression measures is needed.

Adolescents with substance use disorder and assent/consent: Empirical data on understanding biobank risks in genomic research

OBJECTIVE

This study assessed whether a customized disclosure form increases understanding for adolescents with substance use disorder (SUD) when compared to a standard disclosure for genomic addiction research.

METHOD

We gathered empirical data from adolescents with SUD, family members, former patients followed since adolescence, and community counterparts. The study was conducted in four stages. Stage 1: national experts (n=32) identified current, future, speculative risks of broadly shared biobanks. Stage 2 assessed participants' (n=181) understanding of current risks as a prerequisite for rating saliency of risks via a Visual Analog Scale. Salient risks were incorporated into a customized disclosure form. Stage 3 compared the understanding of customized disclosure by participants (n=165) at baseline; all groups scored comparably. Stage 4 conducted a direct comparison of the standard disclosure to standard disclosure plus customized disclosure (n=195). Independent t-tests compared understanding in those receiving the standard disclosure to standard disclosure plus customized disclosure within 6 groups.

RESULTS

The customized disclosure significantly improved understanding in adolescent patients (p=0.002) and parents of patients (p=0.006) to the level of their counterparts. The customized disclosure also significantly improved understanding in siblings of former patients (p=0.034). Understanding of standard disclosure in patients versus controls was significantly different (p=0.005). The groups receiving the customized disclosure scored significantly higher. Understanding of the standard disclosure plus customized disclosure in patients versus controls was not significantly different.

CONCLUSION

Adolescents with addictions understand the risks of participating in genomic addiction research as well as their community counterparts when information provided is salient to them.

Opioid Use and Storage Patterns by Patients after Hospital Discharge following Surgery

INTRODUCTION

Opioid-based analgesic therapy represents a cornerstone of pain management after surgery. The recent rise in opioid sales and opioid overdoses suggests it is important to maximize the safety of opioid prescribing after surgery. Given that patients may live with other family members in the home, safe storage and appropriate disposal of excess opioids after hospital discharge are necessary to prevent unintended secondary exposures. Identifying characteristics of patients who are likely to be prescribed excess opioids after surgery may enable more targeted prescription practices and safety interventions. Our study aimed to elucidate patient-reported opioid use patterns and modes of home storage of opioids among patients discharged home after Cesarean section (C-section) and thoracic surgery. Specifically, we sought to identify characteristics of patients who reported using about half or more versus less of the opioids prescribed to them for use after hospital discharge.

METHODS

For this cohort study, we developed a survey on quality of analgesia following hospital discharge, amounts of opioids taken relative to the amount prescribed, reasons for not taking all prescribed medications, and storage and disposal methods for leftover opioids. Adult patients, who had C-section or thoracic surgery at a tertiary academic medical center, were given a web-based self-administered survey after discharge. Descriptive statistics (means and standard deviations, proportions) were used to describe the study sample and survey results. Comparisons between patients who reported taking about half or more versus less of the opioids prescribed to them for use after hospital discharge were made using unpaired t-tests, Mann-Whitney tests, and Chi-square tests as appropriate.

RESULTS

The majority (53%) of respondents after C-section (N = 30) reported taking either no or very few (less than 5) prescribed opioid pills; 83% reported taking half or less; and 17% of women, reported taking all or nearly all (5 or fewer pills left over) of their opioid prescription. In a cohort of patients after thoracic surgery (n = 31) 45% reported taking either no or very few (5 or less) prescribed opioid pills; 71% reported taking half or less; and 29% of patients reported taking all or nearly all (5 or fewer pills left over) of their opioid prescription. In both cohorts, use of opioids while hospitalized was higher in the group reporting using about half or more of prescribed opioids after discharge. Leftover opioids were stored in an unlocked location in 77% and 73% of cases following C-section and thoracic surgery, respectively.

CONCLUSION

Our findings from surveys in two distinct patient populations at a single academic medical center suggest that current opioid prescribing practices for pain management at hospital discharge following Cesarean section and thoracic surgery may not account for individual patients' analgesic requirements. Excess opioid pills are commonly stored in unsecured locations and represent a potential source for non-medical opioid use and associated morbidity and mortality in patients and their families. Research to develop goal-directed and patient-centered post-discharge opioid prescription practices and encourage opioid safety practices after surgery is needed.

Bivariate Trajectories of Substance Use and Antisocial Behavior: Associations with Emerging Adult Outcomes in a High-Risk Sample

Substance use and antisocial behavior are complex, interrelated behaviors. The current study identified model trajectory classes defined by concurrent substance use and antisocial behavior and examined trajectory associations with emerging adult outcomes. Participants from a high-risk sample of youth (n=536; 73% male) completed interviews at baseline (mean age= 16.1 years) and followup (mean age= 22.6 years). Latent class growth analyses identified five trajectory classes based on alcohol/drug use (AOD) and antisocial behavior (ASB): Dual Chronic, Increasing AOD/Persistent ASB, Persistent AOD/Adolescent ASB, Decreasing Drugs/Persistent ASB, and Resolved. Many individuals (56%) exhibited elevated/increasing AOD, and most (91%) reported ASB decreases. Those associated with the Dual Chronic class had the highest rates of substance dependence, antisocial personality disorder (ASPD), and negative psychosocial outcomes. There were no differences in adult role attainment across classes. Conjoint examination of these behaviors provides greater detail regarding clinical course and can inform secondary prevention and intervention efforts.

Genome-Wide Association Study of Behavioral Disinhibition in a Selected Adolescent Sample

Behavioral disinhibition (BD) is a quantitative measure designed to capture the heritable variation encompassing risky and impulsive behaviors. As a result, BD represents an ideal target for discovering genetic loci that predispose individuals to a wide range of antisocial behaviors and substance misuse that together represent a large cost to society as a whole. Published genome-wide association studies (GWAS) have examined specific phenotypes that fall under the umbrella of BD (e.g. alcohol dependence, conduct disorder); however no GWAS has specifically examined the overall BD construct. We conducted a GWAS of BD using a sample of 1,901 adolescents over-selected for characteristics that define high BD, such as substance and antisocial behavior problems, finding no individual locus that surpassed genome-wide significance. Although no single SNP was significantly associated with BD, restricted maximum likelihood analysis estimated that 49.3 % of the variance in BD within the Caucasian sub-sample was accounted for by the genotyped SNPs (p = 0.06). Gene-based tests identified seven genes associated with BD (p ≤ 2.0 × 10(-6)). Although the current study was unable to identify specific SNPs or pathways with replicable effects on BD, the substantial sample variance that could be explained by all genotyped SNPs suggests that larger studies could successfully identify common variants associated with BD.

Examination of genetic variation in GABRA2 with conduct disorder and alcohol abuse and dependence in a longitudinal study

Previous studies have shown associations between single nucleotide polymorphisms (SNPs) in gamma aminobutyric acid receptor alpha 2 (GABRA2) and adolescent conduct disorder (CD) and alcohol dependence in adulthood, but not adolescent alcohol dependence. The present study was intended as a replication and extension of this work, focusing on adolescent CD, adolescent alcohol abuse and dependence (AAD), and adult AAD. Family based association tests were run using Hispanics and non-Hispanic European American subjects from two independent longitudinal samples. Although the analysis provided nominal support for an association with rs9291283 and AAD in adulthood and CD in adolescence, the current study failed to replicate previous associations between two well replicated GABRA2 SNPs and CD and alcohol dependence. Overall, these results emphasize the utility of including an independent replication sample in the study design, so that the results from an individual sample can be weighted in the context of its reproducibility.

Prevalence and correlates of alcohol and cannabis use disorders in the United States: results from the national longitudinal study of adolescent health

BACKGROUND

Limited current information on the epidemiology of lifetime alcohol and cannabis use disorders in the United States is available.

AIMS

To present detailed information about the prevalence and sociodemographic correlates of lifetime alcohol and cannabis use disorders rates in the United States. To examine gender differences in hazard ratios for the onset of alcohol and cannabis dependence.

METHODS

Participants in Wave IV of the National Longitudinal Study of Adolescent Health (N=15,500, age range: 24-32) were interviewed between 2008 and 2009. Participants who exceeded screening thresholds were queried about lifetime DSM-IV alcohol and marijuana abuse and dependence symptoms. Age of substance dependence onset was queried.

RESULTS

Lifetime rates of alcohol abuse and dependence were 11.8 and 13.2%. Lifetime rates of cannabis abuse and dependence were 3.9 and 8.3%. Lifetime alcohol and cannabis dependence onset peaks were 23 and 20. Correlates of lifetime alcohol abuse included being male (OR 1.4), African-American (OR 0.7), income in the 2nd or 3rd quartile (OR 0.7 and 0.6). Correlates of lifetime alcohol dependence were: being male (OR 1.8), African-American (OR 0.5), and never being married (OR 1.5), and regions outside of the west (Midwest OR 0.7, South OR 0.6, Northeast OR 0.6). Correlates of cannabis abuse and dependence were being male (OR 1.8 and 1.4).

CONCLUSIONS

Lifetime alcohol and cannabis use disorders are highly prevalent in the US population. Men are at higher risk for alcohol and cannabis use disorders. Alcohol use disorders demonstrated specific sociodemographic correlates while marijuana use disorders did not.

MAOA genotype, childhood maltreatment, and their interaction in the etiology of adult antisocial behaviors

BACKGROUND

Maltreatment by an adult or caregiver during childhood is a prevalent and important predictor of antisocial behaviors in adulthood. A functional promoter polymorphism in the monoamine oxidase A (MAOA) gene has been implicated as a moderating factor in the relationship between childhood maltreatment and antisocial behaviors. Although there have been numerous attempts at replicating this observation, results remain inconclusive.

METHODS

We examined this gene-environment interaction hypothesis in a sample of 3356 white and 960 black men (aged 24-34) participating in the National Longitudinal Study of Adolescent Health.

RESULTS

Primary analysis indicated that childhood maltreatment was a significant risk factor for later behaviors that violate rules and the rights of others (p < .05), there were no main effects of MAOA genotype, and MAOA genotype was not a significant moderator of the relationship between maltreatment and antisocial behaviors in our white sample. Post hoc analyses identified a similar pattern of results among our black sample in which maltreatment was not a significant predictor of antisocial behavior. Post hoc analyses also revealed a main effect of MAOA genotype on having a disposition toward violence in both samples and for violent convictions among our black sample. None of these post hoc findings, however, survived correction for multiple testing (p > .05). Power analyses indicated that these results were not due to insufficient statistical power.

CONCLUSIONS

We could not confirm the hypothesis that MAOA genotype moderates the relationship between childhood maltreatment and adult antisocial behaviors.

Distinct loci in the CHRNA5/CHRNA3/CHRNB4 gene cluster are associated with onset of regular smoking

Neuronal nicotinic acetylcholine receptor (nAChR) genes (CHRNA5/CHRNA3/CHRNB4) have been reproducibly associated with nicotine dependence, smoking behaviors, and lung cancer risk. Of the few reports that have focused on early smoking behaviors, association results have been mixed. This meta-analysis examines early smoking phenotypes and SNPs in the gene cluster to determine: (1) whether the most robust association signal in this region (rs16969968) for other smoking behaviors is also associated with early behaviors, and/or (2) if additional statistically independent signals are important in early smoking. We focused on two phenotypes: age of tobacco initiation (AOI) and age of first regular tobacco use (AOS). This study included 56,034 subjects (41 groups) spanning nine countries and evaluated five SNPs including rs1948, rs16969968, rs578776, rs588765, and rs684513. Each dataset was analyzed using a centrally generated script. Meta-analyses were conducted from summary statistics. AOS yielded significant associations with SNPs rs578776 (beta = 0.02, P = 0.004), rs1948 (beta = 0.023, P = 0.018), and rs684513 (beta = 0.032, P = 0.017), indicating protective effects. There were no significant associations for the AOI phenotype. Importantly, rs16969968, the most replicated signal in this region for nicotine dependence, cigarettes per day, and cotinine levels, was not associated with AOI (P = 0.59) or AOS (P = 0.92). These results provide important insight into the complexity of smoking behavior phenotypes, and suggest that association signals in the CHRNA5/A3/B4 gene cluster affecting early smoking behaviors may be different from those affecting the mature nicotine dependence phenotype.

Prevalence and predictors of injection drug use and risky sexual behaviors among adolescents in substance treatment

BACKGROUND AND OBJECTIVES

The longitudinal risk for human immunodeficiency virus (HIV) infection following adolescent substance treatment is not known. Therefore, it is not known if adolescent substance treatment should include HIV prevention interventions. To address this important research gap, this study evaluates the longitudinal prevalence and predictors of injection drug use (IDU) and sex risk behaviors among adolescents in substance treatment.

METHODS

Participants were 260 adolescents (13-18 years) in substance treatment and 201 community control adolescents (11-19 years). Participants were assessed at baseline and follow-up (mean time between assessments = 6.9 years for the clinical sample and 5.6 years for the community control sample). Outcomes included self-report lifetime history of IDU, number of lifetime sex partners and frequency of unprotected sexual intercourse.

RESULTS

At baseline, 7.5% of the clinical sample, compared to 1.0% of the community control sample had a lifetime history of IDU (χ12=10.53, p = .001). At follow-up, 17.4% of the clinical sample compared to 0% of the community control sample had a lifetime history of IDU (χ12=26.61, p = .0005). The number of baseline substance use disorders and onset age of marijuana use significantly predicted the presence of lifetime IDU at follow-up, after adjusting for baseline age, race, and sex. The clinical sample reported more lifetime sex partners and more frequent unprotected sex than the community control sample at baseline and follow-up.

CONCLUSIONS

Many adolescents in substance treatment develop IDU and report persistent risky sex. Effective risk reduction interventions for adolescents in substance treatment are needed that address both IDU and risky sex.

Stability and change of genetic and environmental effects on the common liability to alcohol, tobacco, and cannabis DSM-IV dependence symptoms

This study investigated the stability of genetic and environmental effects on the common liability to alcohol, tobacco, and cannabis dependence across adolescence and young adulthood. DSM-IV symptom counts from 2,361 adolescents were obtained using a structured diagnostic interview. Several sex-limited longitudinal common pathway models were used to examine gender differences in the magnitude of additive genetic (A), shared environment, and non-shared environmental effects over time. Model fitting indicated limited gender differences. Among older adolescents (i.e., age > 14), the heritability of the latent trait was estimated at 0.43 (0.05, 0.94) during the first wave and 0.63 (0.21, 0.83) during the second wave of assessment. A common genetic factor could account for genetic influences at both assessments, as well as the majority of the stability of SAV over time [rA = 1.00 (0.55, 1.00)]. These results suggest that early genetic factors continue to play a key role at later developmental stages.

Prospective effects of adolescent indicators of behavioral disinhibition on DSM-IV alcohol, tobacco, and illicit drug dependence in young adulthood

OBJECTIVE

To identify robust predictors of drug dependence.

METHODS

This longitudinal study included 2361 male and female twins from an ongoing longitudinal study at the Center for Antisocial Drug Dependence (CADD) at the University of Colorado Boulder and Denver campuses. Twins were recruited for the CADD project while they were between the ages of 12 and 18. Participants in the current study were on average approximately 15years of age during the first wave of assessment and approximately 20years of age at the second wave of assessment. The average time between assessments was five years. A structured interview was administered at each assessment to determine patterns of substance use and Diagnostic and Statistical Manual of Mental Disorders (DSM-IV; Fourth Edition) attention deficit hyperactivity disorder (ADHD), conduct disorder (CD), and drug dependence symptoms. Cloninger's Tridimensional Personality Questionnaire was also used to assess novelty seeking tendencies (NS). At the second wave of assessment, DSM-IV dependence symptoms were reassessed using the same interview. Path analyses were used to examine direct and indirect mechanisms linking psychopathology and drug outcomes.

RESULTS

Adolescent substance use, CD, and NS predicted young adult substance dependence, whereas the predictive effects of ADHD were few and inconsistent. Furthermore, CD and NS effects were partially mediated by adolescent substance use.

CONCLUSIONS

Adolescent conduct problems, novelty seeking, and drug use are important indices of future drug problems. The strongest predictor was novelty seeking.

Nominal association with CHRNA4 variants and nicotine dependence

Nicotine binds to nicotinic acetylcholine receptors and studies in animal models have shown that α4β2 receptors mediate many behavioral effects of nicotine. Human genetics studies have provided support that variation in the gene that codes for the α4 subunit influences nicotine dependence (ND), but the evidence for the involvement of the β2 subunit gene is less convincing. In this study, we examined the genetic association between variation in the genes that code for the α4 (CHRNA4) and β2 (CHRNB2) subunits of the nicotinic acetylcholine receptor and a quantitative measure of lifetime DSM-IV ND symptom counts. We performed this analysis in two longitudinal family-based studies focused on adolescent antisocial drug abuse: the Center on Antisocial Drug Dependence (CADD, N = 313 families) and Genetics of Antisocial Drug Dependence (GADD, N = 111 families). Family-based association tests were used to examine associations between 14 single nucleotide polymorphisms (SNPs) in CHRNA4 and CHRNB2 and ND symptoms. Symptom counts were corrected for age, sex and clinical status prior to the association analysis. Results, when the samples were combined, provided modest evidence that SNPs in CHRNA4 are associated with ND. The minor allele at both rs1044394 (A; Z = 1.988, P = 0.047, unadjusted P-value) and rs1044396 (G; Z = 2.398, P = 0.017, unadjusted P-value) was associated with increased risk of ND symptoms. These data provide suggestive evidence that variation in the α4 subunit of the nicotinic acetylcholine receptor may influence ND liability.

Genetic etiology of the common liability to drug dependence: evidence of common and specific mechanisms for DSM-IV dependence symptoms

BACKGROUND

We investigated the etiological nature of comorbid alcohol, tobacco, and cannabis DSM-IV dependence symptoms in late adolescence and young adulthood while accounting for gender differences in the magnitude of genetic and environmental influences.

METHODS

Univariate and multivariate twin modeling was used to determine the heritability of each substance and the etiology of multiple drug problems in a sample of 2484 registrants of the Center for Antisocial Drug Dependence who provided data at the second wave of an ongoing longitudinal study. We report on mean and prevalence levels of whole-life DSM-IV dependence symptoms that were assessed with the Composite International Diagnostic Interview-Substance Abuse Module. Biometrical analyses were limited to age-adjusted DSM-IV dependence symptom counts from a subset of twins that reported using alcohol, tobacco, or cannabis in their lifetime.

RESULTS

Male and female alcohol, tobacco, and cannabis DSM-IV symptoms are indicators of a heritable unidimensional latent continuous trait. Additive genetic factors explain more than 60% of the common liability to drug dependence. A larger proportion of the variation in each substance is attributable to substance-specific genetic and environmental factors.

CONCLUSIONS

These data suggest that both common and substance-specific genetic and environmental factors contribute to individual differences in the levels of DSM-IV alcohol, tobacco, and cannabis dependence symptoms.

Subjective effects for alcohol, tobacco, and marijuana association with cross-drug outcomes

METHODS

The cross-drug relationship of subjective experiences between alcohol, tobacco, and marijuana and problem drug use behaviors were examined. Data were drawn from 3853 individuals between the ages of 11 and 30 years of age participating in the Colorado Center on Antisocial Drug Dependence [CADD]. Subjective experiences were assessed using a 13-item questionnaire that included positive and negative responses for alcohol, tobacco, and marijuana. Lifetime abuse and dependence on these three drugs was assessed using the Composite International Diagnostic Interview, Substance Abuse Module [CIDI-SAM].

RESULTS

Positive and negative subjective experience scales were similar for alcohol, tobacco, and marijuana, although the hierarchical ordering of items differed by drug. Subjective experience scales for each of the three drugs examined correlated significantly, with the strongest relationship being for alcohol and marijuana experiences. Significant associations were identified between how a person experienced a drug and abuse and dependence status for the same or different drug.

CONCLUSION

Cross-drug relationships provide evidence for a common liability or sensitivity towards responding in a similar manner to drugs of abuse within and across different pharmacological classes.

Dizziness and the genetic influences on subjective experiences to initial cigarette use

AIM

To examine individual differences in positive and negative subjective experiences to initial cigarette use.

DESIGN

Retrospective self-reports of initial subjective experiences were examined to estimate the genetic and environmental influences and the extent of their covariation across different effects.

PARTICIPANTS

Data was drawn from 2482 young adult same-and opposite sex twins- and siblings participating in the National Longitudinal Study of Adolescent Health.

MEASUREMENT

Subjective experiences were retrospectively collected using the Early Smoking Experience (ESE) questionnaire.

FINDINGS

Positive experiences evidenced moderate heritable contributions (40%, 95% CI: 0.22 to 0.56), as did an overall hedonic measure (34%, 95% CI: 0.22 to 0.46) and dizziness (34%, 95% CI: 0.15 to 0.52). Negative experiences evidenced small heritable contributions (13%, 95% CI: 0.00 to 0.36). Individual specific environmental influences were strong and accounted for the remaining proportion of observed variation in these experiences. Multivariate genetic modeling identified a moderately heritable underlying factor (37%, 95% CI: 0.22 to 0.52) that influenced the covariation of diverse subjective experiences and loaded most heavily on dizziness. Positive experiences also evidence residual genetic influences that were uncorrelated with other subjective experiences.

CONCLUSIONS

How a person experiences their initial few cigarettes is due to both heritable contributions and environmental experiences unique to the person. The covariation of diverse subjective experiences appears to be due to a heritable latent sensitivity to the chemicals contained in an average cigarette and is best indexed by dizziness.

Common and drug-specific genetic influences on subjective effects to alcohol, tobacco and marijuana use

AIM

To examine variation in positive and negative subjective effects to alcohol, tobacco and marijuana and covariation between these three drugs and each effect.

DESIGN

Retrospective self-reports of subjective effects were collected to estimate the genetic and environmental influences and the extent of their specificity across three drugs.

PARTICIPANTS

Data were drawn from 1299 adolescent and young adult same- and opposite sex twin- and sibling-pairs participating in the Colorado Center for Antisocial Drug Dependence (CADD).

SETTING

A large, collaborative, longitudinal study of substance use and antisocial behavior in community and clinical adolescents.

MEASUREMENT

  Subjective effects were assessed using a 13-item questionnaire that included positive and negative responses to alcohol, tobacco and marijuana.

FINDINGS

Heritable influences contributed moderately (additive genetic effects 16-56%) to positive and negative subjective effects to all three drugs and did not differ for males and females. Genetic and environmental contributions to positive and negative subjective effects are largely non-overlapping for tobacco and marijuana. Multivariate genetic modeling indicated that subjective effects to alcohol, tobacco and marijuana share a common, heritable etiology and that drug-specific genetic influences were an important contributor to individual differences in drug response.

CONCLUSIONS

  Results from our genetic analyses suggest that subjective effects to these commonly used and misused drugs are heritable and that the genetic and environmental influences on effects to one drug also influence subjective effects to other drugs.

Stable genes and changing environments: body mass index across adolescence and young adulthood

The transition between adolescence and young adulthood is a developmentally sensitive time where children are at an increased risk for becoming overweight and developing obesity. Twin studies have reported that body mass index [BMI] is highly heritable, however, it remains unclear whether the genetic influences are sex-limited and whether non-additive genetic influences contribute to body mass index [BMI] during these ages. In the current report, we examined self-reported data on BMI in same [n = 2,744] and opposite-sex [n = 1,178] siblings participating in the National Longitudinal Study on Adolescent Health [Add Health]. To investigate whether the same or different genes contributed to BMI for both sexes, we fit quantitative sex-limited genetic models to three waves of data collection. At each of the three Waves of assessment, models that included additive genetic, individual-specific environment, and no sex-limited genetic influences fit the data most parsimoniously. Heritable effects on BMI at each of the three Waves were large for both sexes and ranged between .75 and .86. While genetic contributions across the ages were highly correlated, longitudinal analyses indicated that the relevant individual-specific environmental influences on BMI in adolescence and young adulthood change sizably. These results underscore the importance of understanding early genetic influences on BMI and highlight the role environmental experiences have at later ages when new genetic influences appear to make a small contribution to individual variation in BMI.