The Causal Role of Alcohol Use in Adolescent Externalizing and Internalizing Problems: A Mendelian Randomization Study

Genetics of child aggression, a systematic review

Excessive and persistent aggressiveness is the most common behavioral problem that leads to psychiatric referrals among children. While half of the variance in childhood aggression is attributed to genetic factors, the biological mechanism and the interplay between genes and environment that results in aggression remains elusive. The purpose of this systematic review is to provide an overview of studies examining the genetics of childhood aggression irrespective of psychiatric diagnosis. PubMed, PsycINFO, and MEDLINE databases were searched using predefined search terms for aggression, genes and the specific age group. From the 652 initially yielded studies, eighty-seven studies were systematically extracted for full-text review and for further quality assessment analyses. Findings show that (i) investigation of candidate genes, especially of MAOA (17 studies), DRD4 (13 studies), and COMT (12 studies) continue to dominate the field, although studies using other research designs and methods including genome-wide association and epigenetic studies are increasing, (ii) the published articles tend to be moderate in sizes, with variable methods of assessing aggressive behavior and inconsistent categorizations of tandem repeat variants, resulting in inconclusive findings of genetic main effects, gene-gene, and gene-environment interactions, (iii) the majority of studies are conducted on European, male-only or male-female mixed, participants. To our knowledge, this is the first study to systematically review the effects of genes on youth aggression. To understand the genetic underpinnings of childhood aggression, more research is required with larger, more diverse sample sets, consistent and reliable assessments and standardized definition of the aggression phenotypes. The search for the biological mechanisms underlying child aggression will also benefit from more varied research methods, including epigenetic studies, transcriptomic studies, gene system and genome-wide studies, longitudinal studies that track changes in risk/ameliorating factors and aggression-related outcomes, and studies examining causal mechanisms.

Mendelian randomization studies of depression: evidence, opportunities, and challenges

BACKGROUND

Major depressive disorder (MDD) poses a significant social and economic burden worldwide. Identifying exposures, risk factors, and biological mechanisms that are causally connected to MDD can help build a scientific basis for disease prevention and development of novel therapeutic approaches.

METHODS

In this systematic review, we assessed the evidence for causal relationships between putative causal risk factors and MDD from Mendelian randomization (MR) studies, following PRISMA. We assessed methodological quality based on key elements of the MR design: use of a full instrumental variable analysis and validation of the three key MR assumptions.

RESULTS

We included methodological details and results from 52 articles. A causal link between lifestyle, metabolic, inflammatory biomarkers, particular pathological states and MDD is supported by MR investigations, although results for each category varied substantially.

CONCLUSIONS

While this review shows how MR can offer useful information for examining prospective treatment targets and better understanding the pathophysiology of MDD, some methodological flaws in the existing literature limit reliability of results and probably underlie their heterogeneity. We highlight perspectives and recommendations for future works on MR in psychiatry.

Alcohol Misuse among English Youth, Are Harms Attributable to Alcohol or to Underlying Disinhibitory Characteristics?

INTRODUCTION

Alcohol use by young people is associated with a range of psychological and physical harms. However, similar harms are also reported with disinhibitory conditions such as conduct problems that are said to precede and predispose to alcohol misuse. We explored whether alcohol use or indicators of underlying disinhibition predict psychological and physical harms in a cohort of young people.

METHODS

We used data from a randomised controlled intervention trial that identified young people who consumed alcohol (n = 756), mean age = 15.6 years, attending emergency departments (EDs) in England. Disinhibition was measured by the self-report Strengths and Difficulties Questionnaire hyperactivity and conduct problem items, and alcohol-related harms by questions from the ESPAD, a major European school survey. We conducted a mediation analysis with a primary outcome of frequency of engaging in alcohol-related harms 12 months after screening in ED, exploring for the mediating influence of alcohol consumed at six months. We included age, gender, allocated group and baseline consumption as covariates and adjusted for the multi-level nature of the study, where young people were nested within EDs.

RESULTS

Conduct problems and to a lesser extent hyperactivity predicted harms at twelve months. This effect was not mediated by alcohol consumed at 6 months.

CONCLUSIONS

Among young drinkers underlying behavioural attributes predict harm independently of alcohol use. This suggests that the harms associated with alcohol use are attributable more to underlying disinhibitory characteristics than the quantity of alcohol consumed.

Family, personal, parental correlates and behavior disturbances in school-aged boys with attention-deficit/hyperactivity disorder (ADHD): a cross-sectional study

BACKGROUND

To evaluate the relationship among family, personal, parental correlates, and behavioral disturbances in boys with attention-deficit/hyperactivity disorder (ADHD).

METHODS

We performed a hospital-based cross-sectional study. School-aged boys who first visited the hospital between 2000 and 2011 with ADHD were identified. Through medical records review, demographic information, family characteristics, personal characteristics, parental characteristics, and the Child Behavior Checklist (CBCL) collected during the first outpatient visit were retrieved. A T-score higher than 63 in the internalizing or externalizing subscale of the CBCL indicated severe behavioral disturbances in each domain. Multivariable logistic regression was used to evaluate the relationship between the correlates and behavioral disturbances. Eligible patients were further classified into groups without behavioral disturbance, with either only severe internalizing or only severe externalizing behaviors, or with both behaviors. Multivariable ordinal logistic regression was used to investigate the association between the correlates and the number of types of behavioral disturbances.

RESULTS

A total of 1855 boys with ADHD were included. In the multivariable logistic regression, family factors, including being first-born, living in a family not with both parents, and family history of mental disorder, were associated with severe internalizing and externalizing behaviors. Personal factors, including prenatal complications, perinatal complications, and medical and psychiatric comorbidities, were associated with severe internalizing behaviors, but only prenatal complications and medical comorbidities were associated with severe externalizing behaviors. Parental factors were only associated with severe externalizing behaviors. A higher paternal education level had a protective effect, but younger motherhood increased the risk. In ordinal logistic regression, these factors were also associated with more types of behavioral disturbances.

CONCLUSIONS

Multiple factors are related to behavioral disturbances in ADHD. Our study reported the association among family, personal, parental factors, severe internalizing behavior, severe externalizing behavior, and number of behavioral disturbances in boys with ADHD. However, the impacts differed as the behavior phenotypes varied. Further research is needed to better understand the heterogeneity of ADHD behavior.

'No, you should not beat our child because he will become aggressive:' Applying a multi-method approach to explore intergenerational transmission of parenting practices

BACKGROUND

Exploring the cultural context of intergenerational continuity of warm and harsh parenting informs parents motivations to adopt specific parenting behaviours.

OBJECTIVE

Parents' perceptions of being parented in the past and their current parenting as well as adolescents' perceptions of current parenting were explored applying a multi-method approach.

METHODS

Following written informed consent, a total of 24 interviews with 10 families (dyads of 14 parents and ten adolescents) from Udupi taluk in southern India was conducted. In the first stage, in-depth interviews were conducted with parent participants (Generation 1 (G1)) and in the second stage, adolescents (Generation 2 (G2)) participated in the photovoice component. Multiple forms of data including photographs, journals and interviews facilitated using the SHOWeD model were collected and were analysed thematically using ATLAS.ti(v.8).

RESULTS

Subtle changes in reinforcing culture-specific gender norms between generations were elicited. Differences in communication, granting autonomy to female adolescents, and in disciplining methods between G1 and G2 were observed. Warm parenting was transmitted between generations while harsh parenting in G1 in the presence of external social support was discarded in favor of warm parenting in G2.

CONCLUSION

We provide evidence for perceptions of parenting and adolescent behaviors across two generations. Transmission of warm parenting and interruption in the cycle of harsh parenting in the presence of external social support were significant findings. Related theoretical and methodological applications are discussed.

Using Mendelian randomization analysis to better understand the relationship between mental health and substance use: a systematic review

BACKGROUND

Poor mental health has consistently been associated with substance use (smoking, alcohol drinking, cannabis use, and consumption of caffeinated drinks). To properly inform public health policy it is crucial to understand the mechanisms underlying these associations, and most importantly, whether or not they are causal.

METHODS

In this pre-registered systematic review, we assessed the evidence for causal relationships between mental health and substance use from Mendelian randomization (MR) studies, following PRISMA. We rated the quality of included studies using a scoring system that incorporates important indices of quality, such as the quality of phenotype measurement, instrument strength, and use of sensitivity methods.

RESULTS

Sixty-three studies were included for qualitative synthesis. The final quality rating was '-' for 16 studies, '- +' for 37 studies, and '+'for 10 studies. There was robust evidence that higher educational attainment decreases smoking and that there is a bi-directional, increasing relationship between smoking and (symptoms of) mental disorders. Another robust finding was that higher educational attainment increases alcohol use frequency, but decreases binge-drinking and alcohol use problems, and that mental disorders causally lead to more alcohol drinking without evidence for the reverse.

CONCLUSIONS

The current MR literature increases our understanding of the relationship between mental health and substance use. Bi-directional causal relationships are indicated, especially for smoking, providing further incentive to strengthen public health efforts to decrease substance use. Future MR studies should make use of large(r) samples in combination with detailed phenotypes, a wide range of sensitivity methods, and triangulate with other research methods.

Investigating causality between liability to ADHD and substance use, and liability to substance use and ADHD risk, using Mendelian randomization

Attention-deficit hyperactivity disorder (ADHD) has consistently been associated with substance use, but the nature of this association is not fully understood. To inform intervention development and public health messages, a vital question is whether there are causal pathways from ADHD to substance use and/or vice versa. We applied bidirectional Mendelian randomization, using summary-level data from the largest available genome-wide association studies (GWAS) on ADHD, smoking (initiation, cigarettes per day, cessation, and a compound measure of lifetime smoking), alcohol use (drinks per week, alcohol problems, and alcohol dependence), cannabis use (initiation), and coffee consumption (cups per day). Genetic variants robustly associated with the "exposure" were selected as instruments and identified in the "outcome" GWAS. Effect estimates from individual genetic variants were combined with inverse-variance weighted regression and five sensitivity analyses (weighted median, weighted mode, MR-Egger, generalized summary data-based MR, and Steiger filtering). We found evidence that liability to ADHD increases likelihood of smoking initiation and heaviness of smoking among smokers, decreases likelihood of smoking cessation, and increases likelihood of cannabis initiation. There was weak evidence that liability to ADHD increases alcohol dependence risk but not drinks per week or alcohol problems. In the other direction, there was weak evidence that smoking initiation increases ADHD risk, but follow-up analyses suggested a high probability of horizontal pleiotropy. There was no clear evidence of causal pathways between ADHD and coffee consumption. Our findings corroborate epidemiological evidence, suggesting causal pathways from liability to ADHD to smoking, cannabis use, and, tentatively, alcohol dependence. Further work is needed to explore the exact mechanisms mediating these causal effects.

Punch-Drunk or Drunken Boxing? The Etiology of Alcohol-Related Physical Violence through Adolescence and Young Adulthood

BACKGROUND

Alcohol-related physical violence (ARPV) can be a causal consequence of alcohol consumption, but only for specific individuals (e.g., those predisposed to violence). Studies have not accounted for the shared etiology explaining comorbidity between alcohol use and violent behavior as a potential third-variable explanation of ARPV. The current study examined genetically-informed associations between ARPV, heavy alcohol use (HAU) and overall physical violence (OPV) in adolescence and young adulthood, by testing two proposed theories of ARPV processes (HAU causes ARPV, causal relationships depend upon OPV) and how overarching shared covariance may account for these associations.

METHODS

Using the twin and sibling subsample from the National Longitudinal Study of Adolescent to Adult Health (Add Health), a series of biometric models tested hypotheses individually in adolescence and young adulthood. This included estimating bivariate Cholesky and direction-of-causality models, and trivariate Cholesky, independent pathway, and common pathway models.

RESULTS

HAU had a causal effect on ARPV in adolescence and young adulthood. This effect was not moderated by OPV at either developmental stage. A shared etiology or common latent factor did not explain associations between ARPV, OPV, and HAU, even though ARPV strongly covaried independently with HAU and with OPV. Finally, OPV also had a causal effect on ARPV in adolescence, and in young adulthood for adolescent-onset drinkers.

CONCLUSIONS

Causal theories of ARPV still hold when accounting for shared genetic and environmental variance. Further research on the exact role of violence (predispositions, environmental contexts) is required, as both phenotypes substantially (and separately) explain influences driving ARPV.

Supplemental data for this article is available online at https://doi.org/10.1080/10826084.2021.1887244.

Effect of alcohol use disorders and alcohol intake on the risk of subsequent depressive symptoms: a systematic review and meta-analysis of cohort studies

BACKGROUND AND AIMS

Alcohol use disorders (AUD) are often comorbid with depressive symptoms. Cohort studies on the association between AUD and subsequent depressive symptoms have produced inconsistent results. Moreover, regarding alcohol intake, the risk of developing depressive symptoms might vary with alcohol intake level. We aimed to investigate the association between AUD, alcohol intake and subsequent depressive symptoms.

DESIGN AND SETTING

We conducted a systematic search in PubMed, Embase and PsycINFO for cohort studies on the association between AUD or alcohol intake and subsequent depressive symptoms.

PARTICIPANTS

We included 338 426 participants from 42 studies. Six and four studies analyzed only females and males, respectively.

MEASUREMENTS

We combined risk estimates for developing depressive symptoms using a random-effects model. We divided alcohol intake into abstinence, light (0-84 g/week), moderate (85-168 g/week) and heavy drinking (> 168 g/week or > 48 g/day at least weekly). We conducted a categorical analysis to compare the risk of depressive symptoms between abstinence and different intake categories. Further, we conducted a dose-response analysis to investigate the alcohol-depression association.

FINDINGS

We analyzed 42 studies (follow-up time: 1-40 years). AUD was associated with significantly increased risk of subsequent depressive symptoms [relative risk (RR) = 1.57, 95% confidence interval (CI) = 1.41-1.76]. Regarding alcohol intake, heavy drinking had an increased risk of depressive symptoms; however, the association was only significant when controls were limited to non-heavy drinkers (RR = 1.13, 95% CI = 1.05-1.22). Taking into consideration the possibility of publication bias and confounding factors made the association non-significant. We observed J-shaped associations in both categorical and dose-response analyses where light-moderate drinking had a significantly decreased risk of depression, while heavy drinking did not show a significant association with depressive symptoms compared with non-drinkers.

CONCLUSION

Alcohol use disorders are associated with increased the risk of subsequent depressive symptoms. Heavy drinking does not significantly predict occurrence of depressive symptoms after adjusting for potential confounders.

Alcohol use in late adolescence and early adulthood: The role of generalized anxiety disorder and drinking to cope motives

BACKGROUND

The relationship between anxiety and alcohol use is unclear, and moderating factors, such as drinking to cope (DTC) motives, may explain mixed findings.

METHODS

Using the Avon Longitudinal Study of Parents and Children (ALSPAC), we examined associations between generalized anxiety disorder (GAD) at age 18 and frequent drinking, frequent bingeing, hazardous drinking, and harmful drinking at ages 18 (unadjusted n = 3462) and 21 (unadjusted n = 2076), in a sample of late adolescent drinkers. Analyses were adjusted for sociodemographic, parental, and adolescent confounders. We also examined whether DTC motives influenced the strength and direction of associations between GAD and alcohol use.

RESULTS

GAD was positively associated with all alcohol outcomes at baseline (unadjusted OR (95% CI): frequent drinking 1.40 (1.02-1.91); frequent bingeing 1.40 (0.96-2.04); hazardous drinking 1.44 (1.08-1.92); harmful drinking 1.98 (1.22-3.23)). GAD increased the odds of harmful drinking at age 21 (unadjusted OR 1.72, 95% CI 1.09-2.73), but there was no clear evidence of a longitudinal relationship between GAD and the other alcohol use outcomes. There was no clear evidence of a GAD x DTC interaction on alcohol use at ages 18 or 21. Findings were consistent across various multiply imputed datasets.

CONCLUSIONS

In adolescence, GAD symptoms are associated with frequent drinking, frequent bingeing, hazardous drinking, and harmful drinking. In early adulthood, associations remain for harmful drinking only. DTC motives do not appear to moderate the relationship at either age.

Predictors of Increases in Alcohol Problems and Alcohol Use Disorders in Offspring in the San Diego Prospective Study

BACKGROUND

The 35-year-long San Diego Prospective Study documented 2-fold increases in alcohol problems and alcohol use disorders (AUDs) in young-adult drinking offspring compared to rates in their fathers, the original probands. The current analyses use the same interviews and questionnaires at about the same age in members of the 2 generations to explore multiple potential contributors to the generational differences in adverse alcohol outcomes.

METHODS

Using data from recent offspring interviews, multiple cross-generation differences in characteristics potentially related to alcohol problems were evaluated in 3 steps: first through direct comparisons across probands and offspring at about age 30; second by backward linear regression analyses of predictors of alcohol problems within each generation; and finally third through R-based bootstrapped linear regressions of differences in alcohol problems in randomly matched probands and offspring.

RESULTS

The analyses across the analytical approaches revealed 3 consistent predictors of higher alcohol problems in the second generation. These included the following: (i) a more robust relationship to alcohol problems for offspring with a low level of response to alcohol; (ii) higher offspring values for alcohol expectancies; and (iii) higher offspring impulsivity.

CONCLUSIONS

The availability of data across generations offered a unique perspective for studying characteristics that may have contributed to a general finding in the literature of substantial increases in alcohol problems and AUDs in recent generations. If replicated, these results could suggest approaches to be used by parents, healthcare workers, insurance companies, and industry in their efforts to mitigate the increasing rates of alcohol problems in younger generations.

Explaining the association between anxiety disorders and alcohol use disorder: A twin study

BACKGROUND

It is unknown whether social anxiety disorder (SAD) has a unique association with alcohol use disorder (AUD) over and beyond that of other anxiety disorders, how the associations develop over time, and whether the associations are likely to be causal.

METHODS

Diagnoses of AUD, SAD, generalized anxiety disorder, panic disorder, agoraphobia, and specific phobias were assessed twice using the Composite International Diagnostic Interview among 2,801 adult Norwegian twins. The data were analyzed using logistic regression analyses and multivariate biometric structural equation modeling.

RESULTS

SAD had the strongest association with AUD, and SAD predicted AUD over and above the effect of other anxiety disorders. In addition, SAD was prospectively associated with AUD, whereas other anxiety disorders were not. AUD was associated with a slightly elevated risk of later anxiety disorders other than SAD. Biometric modeling favored a model where SAD influenced AUD compared to models where the relationship was reversed or due to correlated risk factors. Positive associations between AUD and other anxiety disorders were fully explained by shared genetic risk factors.

CONCLUSIONS

Unlike other anxiety disorders, SAD plausibly has a direct effect on AUD. Interventions aimed at prevention or treatment of SAD may have an additional beneficial effect of preventing AUD, whereas interventions aimed at other anxiety disorders are unlikely to have a similar sequential effect on AUD.

Genetics of biologically based psychological differences

In recent years, substantial effort has gone into disentangling the genetic contribution to individual differences in behaviour (such as personality and temperament traits). Heritability estimates from twin and family studies, and more recently using whole genome approaches, suggest a substantial genetic component to these traits. However, efforts to identify the genes that influence these traits have had relatively little success. Here, we review current work investigating the heritability of individual differences in behavioural traits and provide an overview of the results from genome-wide association analyses of these traits to date. In addition, we discuss the implications of these findings for the potential applications of Mendelian randomization.This article is part of the theme issue 'Diverse perspectives on diversity: multi-disciplinary approaches to taxonomies of individual differences'.

Distraction towards contextual alcohol cues and craving are associated with levels of alcohol use among youth

BACKGROUND

Controlling drinking behaviour requires the ability to block out distracting alcohol cues in situations in which drinking is inappropriate or harmful. However, at present few studies have investigated whether distraction and response inhibition to contextual alcohol cues are related to alcohol use in adolescents and young adults. We aimed to investigate whether tendencies towards distraction and failures of response inhibition in the presence of contextual alcohol cues, and alcohol craving were associated with higher levels of alcohol consumption, beyond what could be explained by demographic variables.

METHODS

To test this, 108 participants (Mean age = 21.7, range = 16-27), whom were both drinkers and non-drinkers performed a modified Go/NoGo task tailored to measure distraction and response inhibition in the presence of alcohol cues relative to neutral stimuli. Alcohol craving was assessed using a visual analogue scale of craving for different types of alcohol cues. Levels of alcohol use and problematic alcohol use were assessed using a self-report measure of number of drinking days in the previous month and the Alcohol Use Disorders Identification Test. Data were analysed using sequential multiple regression using a zero-inflated negative binomial distribution model.

RESULTS

Drinking days correlated with distraction but not response inhibition to contextual alcohol cues. Sequential regression analyses revealed that the inclusion of distraction bias accounted for 11% additional variance (significant) in alcohol use, in addition to that explained by demographics alone (17%). Craving for alcohol explained an additional 30% variance (significant) in alcohol use.

CONCLUSIONS

The results reported here support the idea that both biased distraction towards alcohol cues and alcohol craving are associated with preceding drinking days, but not necessarily drinking status. Further studies are warranted that address whether cognitive distraction to alcohol-related cues cause or is an effect of alcohol use among youth.