Measured environmental contributions to cannabis abuse/dependence in an offspring of twins design

Prevalence and correlates of cannabis use disorder among Australians using cannabis products to treat a medical condition

INTRODUCTION

Prior research has examined the prevalence and correlates of cannabis use disorder (CUD) in people who use cannabis; however, these are poorly described for people using cannabis for medical reasons.

METHODS

Data came from a 2018 to 2019 online, anonymous, cross-sectional survey of Australians reporting using either illicit or licit cannabis for medical reasons within the past year. Included were questions on demographics, current and lifetime patterns of cannabis use, clinical conditions for which medical cannabis was used, and individual criteria for CUD and cannabis withdrawal syndrome. Bayesian Horseshoe logistic regression models were used to identify covariates associated with meeting CUD DSM-5 conditions for any-CUD (≥2/11 criteria) and moderate-severe-CUD (≥4/11).

RESULTS

A total of 905 participants were included in the analysis. The majority (98%) used illicit cannabis products. Criteria for any-CUD criteria were met by 290 (32.0%), and 117 (12.9%) met criteria for moderate-severe-CUD. Tolerance (21%) and withdrawal (35%) were the most commonly met criteria. Correlates with the strongest association with CUD were inhaled route of administration [odds ratio (OR) = 2.96, 95% credible interval 1.11, 7.06], frequency of cannabis use (OR = 1.24, 1.11-1.35), proportion of cannabis for medical reasons (OR = 0.83, 0.74, 0.94), frequency of tobacco use (OR = 1.10, 1.03, 1.17), age (OR = 0.75, 0.64, 0.90) and pain as main clinical indication (OR = 0.58, 0.36, 1.00).

DISCUSSION AND CONCLUSIONS

Prevalence of CUD in medical cannabis users appears comparable to 'recreational' users, with many similar correlates. CUD was associated with using cannabis to treat mental health rather than pain conditions and inhaled over other routes of administration.

Transitions in alcohol use over time: a survival analysis

Background

The current study examined the predictors of the onset of alcohol use as well as predictors of remission and relapse, both from heavy drinking and from alcohol dependence. Similarities and differences in both clinical and psychosocial predictors across the transitions were examined.

Methods

A sample of men from the Vietnam Era Twin Registry (N = 1769) completed an assessment of lifetime drinking history, which allowed age markers for starting and stopping different drinking patterns. The men also completed various assessments regarding personality, alcohol motives, and psychiatric diagnoses. Survival analyses were used to examine the predictors of the three transitions of onset, remission, and relapse for the phenotypes of heavy drinking and of alcohol dependence, censoring the individuals who had not yet experienced an event.

Results

As expected, predictors of onset for drinking, heavy drinking, and alcohol dependence were largely consistent and included externalizing symptomology, nicotine dependence, and cotwin history of drinking as risk factors. Predictors of remission from heavy drinking, somewhat similarly to remission from alcohol dependence, included the risk factor of externalizing disorders but also, as predicted, included more risk and protective factors in the psychosocial realm that were not predictors of onset. Contrary to our prediction, relapse to heavy drinking and alcohol dependence were predicted largely by unique psychosocial risk and protective factors including social and coping motives.

Conclusion

Current findings extend the findings of past research to remission and relapse in the later decades of life and have implications for treatment of alcohol use problems.

Attitudes, beliefs, and knowledge of substance use amongst youth in the Eastern Mediterranean region: A systematic review

BACKGROUND

Substance use has a tremendous impact on the burden of disease. This is particularly true in the Eastern Mediterranean region (EMR), where many countries serve as suppliers of drugs. As risk perception and frequency of use are inversely correlated, targeting perception during adolescence becomes essential for prevention. In this study, we systematically reviewed the literature on attitudes, beliefs, and knowledge of substance use amongst youth in the EMR.

METHODS

We reviewed quantitative articles addressing attitudes, beliefs, and knowledge of youth aged between 13 and 25 years towards substance use in the EMR. We searched MEDLINE, PubMed, Cochrane, PsycInfo, and PsycArticles then applied a duplicate independent method for study selection and screening. Two reviewers completed data abstraction and a narrative summary of findings.

RESULTS

Our search generated 12,810 articles. Five cross-sectional studies were eligible (two analytic and three descriptive). The analytic studies described a significant correlation between intention to use and both attitudes and subjective norms. The descriptive studies portrayed a negative attitude towards use with a low threshold for considering it as serious. Beliefs pertaining to reasons for use included stress and sleeping, whereas thoughts on treatment were restricted to traditional methods based on personal resilience and religious support. Knowledge about substance use symptoms, withdrawal, and treatment was low.

CONCLUSION

Our review ascertains the role of sociocultural moral prohibition and awareness of mental health as major influencers in shaping the perception of substance use. Further research is needed to elaborate culturally-tailored survey tools.

Characterizing users of new psychoactive substances using psychometric scales for risk-related behavior

INTRODUCTION

Studies investigating risk-related behavior in relation to new psychoactive substance (NPS) use are sparse. The current study investigated characteristics of NPS users by comparing risk-related behavior of NPS users to that of illicit drugs (ID) users and licit substances users and non-users (NLC) users.

METHODS

In this cross-sectional study we included 528 individuals across an age range of 18-72years. Using a web-based questionnaire we collected self-report data on substance use, sensation seeking, impulsivity, peer substance use and risk perception of substance use.

RESULTS

NPS and ID users had a higher level of sensation seeking compared to NLC users (NPS users: p<0.001; ID users: p<0.001). NPS users (p<0.001), but not ID users (p=0.16), had increased levels of impulsivity compared to NLC users. NPS users had significantly higher scores for sensation seeking (F_1,423=51.52, p<0.001) and impulsivity (F_1,423=6.15, p=0.01) compared to ID users. Additionally, NPS users had significantly more peers who use substances compared to ID and NLC users. Also, NPS and ID users had lower risk perception for most substances than NLC users. NPS users had lower risk perception for most substances than ID users.

CONCLUSIONS

The findings highlight that NPS users show substantial more risk-related behavior than both ID and NLC users. Therefore, NPS users might be considered as a distinctive group of substance users that need another approach in terms of prevention.

The Effects of Excitatory and Inhibitory Social Cues on Cocaine-Seeking Behavior

Social partners influence the likelihood of using drugs, developing a substance use disorder and relapse to drug use after a period of abstinence. Preclinical studies report that social cues influence the acquisition of cocaine use, the escalation of cocaine use over time, and the compulsive patterns of cocaine use that emerge during an extended binge. The purpose of this study was to examine the effects of social cues on the reinstatement of cocaine-seeking behavior after a period of abstinence. Male rats were obtained at weaning, assigned to triads (three rats/cage), reared to adulthood and implanted with intravenous catheters. Rats from each triad were then assigned to one of three conditions: (1) test rats were trained to self-administer cocaine and were tested for reinstatement; (2) cocaine partners were trained to self-administer cocaine and were predictive of response-contingent cocaine delivery; and (3) abstinent partners were not given access to cocaine and were predictive of extinction. The test rats alternated social partners every 5 days for 20 days such that responding was reinforced with cocaine in the presence of the cocaine partner (S⁺) for 10 days and not reinforced with cocaine in the presence of the abstinent partner (S⁻) for 10 days. Responding of the test rats was then extinguished over 7 days under isolated conditions. Tests of reinstatement were then conducted in the presence of the cocaine partner and abstinent partner under extinction conditions. Neither social partner reinstated responding relative to that observed on the final day of extinction; however, responding was greater in the presence of the cocaine partner (S⁺) than the abstinent partner (S⁻) during the reinstatement test. These data fail to demonstrate that a social partner reinstates cocaine-seeking behavior after a period of abstinence, but they do indicate that social partners can serve as either excitatory or inhibitory discriminative stimuli to influence drug-seeking responses.

Alcohol problem recognition and help seeking in adolescents and young adults at varying genetic and environmental risk

INTRODUCTION

Alcohol use disorder symptoms frequently occur in adolescents and younger adults who seldom acknowledge a need for help. We identified sociodemographic, clinical, and familial predictors of alcohol problem recognition and help seeking in an offspring of twin sample.

METHOD

We analyzed longitudinal data from the Children of Alcoholics and Twins as Parents studies, which are combinable longitudinal data sources due to their equivalent design. We analyzed respondents (n=1073, 56.0% of the total sample) with alcohol use disorder symptoms at the baseline interview. Familial characteristics included perceptions of alcohol problems and help seeking for alcohol problems within the immediate family and a categorical variable indicating genetic and environmental risk. We used logistic regression to examine predictors of alcohol problem recognition and help seeking.

RESULTS

Approximately 25.9% recognized their alcohol problems and 26.7% sought help for drinking. In covariate-adjusted analyses, help seeking among family members predicted problem recognition, several clinical characteristics predicted both problem recognition and help seeking, and familial risk predicted help seeking. Alcohol problem recognition mediated the association between alcohol use disorder symptoms and incident help seeking.

CONCLUSIONS

Facilitating the self-recognition of alcohol use disorder symptoms, and perhaps the awareness of family members' help seeking for alcohol problems, may be potentially promising methods to facilitate help seeking.

Parental Separation and Offspring Alcohol Involvement: Findings from Offspring of Alcoholic and Drug Dependent Twin Fathers

BACKGROUND

We examined associations between parental separation during childhood and offspring alcohol involvement, adjusting for genetic and environmental risks specific to parental alcohol (AD) and cannabis/other illicit drug dependence (DD).

METHODS

The sample consisted of 1,828 offspring of male twins from the Vietnam Era Twin (VET) Registry, who completed a telephone diagnostic interview. Cox proportional hazards regression analyses were conducted predicting onset of first use, transition from first use to first AD symptom, and transition from first use to AD diagnosis from paternal and avuncular AD and DD history, parental separation, and offspring and family background characteristics. Paternal/avuncular DD/AD was based on the DSM-III-R; offspring and maternal AD were based on DSM-IV criteria.

RESULTS

Paternal DD/AD predicted increased offspring risk for all transitions, with genetic effects suggested on rate of transitioning to AD diagnosis. Parental separation was predictive of increased risk for early alcohol use, but a reduced rate of transition to both AD symptom onset and onset of AD. No interactions between separation and familial risk (indexed by paternal or avuncular DD/AD) were found.

CONCLUSIONS

Findings highlight the contribution of both parental separation and paternal substance dependence in predicting timing of offspring alcohol initiation and problems across adolescence into early adulthood.

Substance abuse In Middle Eastern adolescents living in two different countries: spiritual, cultural, family and personal factors

It is estimated that the percentage of students using illicit substances by sixth grade has tripled over the last decade not only in developed countries but in developing countries as well probably due to the transition to a more Western society. Although much has been done to understand the mechanisms underlying substance abuse, few studies have been conducted with minority ethnic and religious groups such as Middle Eastern Youth. The primary goal of this study was to determine whether there are differences in factors contributing to substance abuse in adolescents from Lebanon versus the U.S.A. and to decipher the role of spirituality, religion, and culture among other factors that may influence substance abuse. A correlational cross-sectional design was used with adolescents living in two different countries: Los Angeles, California and Beirut, Lebanon. Muslim adolescents had significantly less rates of alcohol and substance use than Christians in both Lebanon and Los Angeles. More years lived in the U.S.A. increases the likelihood of abuse for both Muslims and Christians. Attachment to God and family was negatively associated with substance abuse. These results among others facilitate a better understanding of the influence of culture, religion, family and personal factors on substance abuse. Culturally sensitive interventions could benefit from the findings of this pilot study.

Trends in detection rates of risky marijuana use in Colorado health care settings

BACKGROUND

Over the past several years, many states, including Colorado, have approved medical marijuana legislation. There is concern that increased access to and visibility of medical marijuana may lead to harmful use.

METHODS

This study examined changes in patients' marijuana use in 12 health care settings through a statewide screening, brief intervention, and referral to treatment (SBIRT) initiative.

RESULTS

Beginning in 2009, the odds of screening positive for risk-prone marijuana use significantly increased, coinciding with dramatic increases in use of Colorado's medical marijuana program. Young males were most likely to screen positive. Among users, there was a small, statistically significant increase in severity of use over time.

CONCLUSIONS

Findings suggest that health care providers may be serving increasing numbers of patients using marijuana for medical or recreational purposes.

Individuality and contextual influences on drug dependence: a 15-year Prospective longitudinal study of adolescents from Harlem

In this 15-year longitudinal study the authors investigated individual and contextual factors that predispose adolescents from a disadvantaged urban area to drug dependence in adulthood. Adolescents were recruited from schools serving East Harlem in New York City. Of the 838 participants followed to adulthood, 59% were women, 55% were African American, and 45% were Puerto Rican. Self-report data were obtained on externalizing and internalizing problems, substance use, and contextual influences across adolescence and young adulthood. Drug dependence was assessed in adulthood. Multivariate logistic regressions of drug dependence were performed on the whole sample and separately by gender. Each of the domains was associated with adult drug dependence. Although mean gender differences were found, most associations of risk factors with drug dependence did not vary significantly by gender. Treating externalizing and internalizing problems, reducing substance use, and providing coping skills for adverse contextual influences in adolescence and young adulthood may reduce the likelihood of becoming drug dependent in adulthood.

Parent, sibling and peer associations with subtypes of psychiatric and substance use disorder comorbidity in offspring

BACKGROUND

Parental substance use disorder (SUD) is associated with a range of negative offspring outcomes and psychopathology, but the clustering of these outcomes into subtypes has seldom been examined, nor have the familial and environmental contexts of these subtypes been reported. The present study examines the clustering of offspring lifetime substance use and psychiatric disorders into subtypes and characterizes them in terms of familial and non-familial influences using an offspring-of-twins design.

METHOD

Telephone-administered diagnostic interviews were used to collect data on psychiatric disorders and SUD from 488 twin fathers, 420 biological mothers and 831 offspring. Latent class analysis (LCA) was used to derive subtypes of lifetime comorbidity in offspring. Familial risk and environmental variables associated with each subtype (i.e., parenting, childhood physical or sexual abuse, perceived sibling and peer substance use) were identified using multinomial logistic regression.

RESULTS

Four classes identified by LCA were characterized as (1) unaffected, (2) alcohol abuse/dependence, (3) alcohol abuse/dependence comorbid with anxiety and depression, and (4) alcohol, cannabis abuse/dependence and nicotine dependence comorbid with conduct disorder. Inconsistent parenting, childhood physical/sexual abuse, and perceived sibling and peer substance use were significantly associated with profiles of offspring comorbidity after adjusting for familial vulnerability. Some associations were specific (i.e., perceived peer alcohol use to the AUD class), while others were general (peer smoking to all 3 comorbidity classes).

CONCLUSIONS

We observed distinct subtypes of psychiatric and SUD comorbidity in adolescents and young adults. Subtypes of offspring psychopathology have varied associations with parental psychopathology, family environment, and sibling and peer behaviors.

The third rail of family systems: sibling relationships, mental and behavioral health, and preventive intervention in childhood and adolescence

Sibling relationships are an important context for development, but are often ignored in research and preventive interventions with youth and families. In childhood and adolescence, siblings spend considerable time together, and siblings' characteristics and sibling dynamics substantially influence developmental trajectories and outcomes. This paper reviews research on sibling relationships in childhood and adolescence, focusing on sibling dynamics as part of the family system and sibling influences on adjustment problems, including internalizing and externalizing behaviors and substance use. We present a theoretical model that describes three key pathways of sibling influence: one that extends through siblings' experiences with peers and school, and two that operate largely through family relationships. We then describe the few existing preventive interventions that target sibling relationships and discuss the potential utility of integrating siblings into child and family programs.

Parent, sibling and peer influences on smoking initiation, regular smoking and nicotine dependence. Results from a genetically informative design

We sought to determine whether parenting, sibling and peer influences are associated with offspring ever smoking, regular smoking and nicotine dependence (ND) after controlling for familial factors. We used a twin-family design and data from structured diagnostic surveys of 1919 biological offspring (ages 12-32 years), 1107 twin fathers, and 1023 mothers. Offspring were classified into one of four familial risk groups based on twin fathers' and their co-twins' history of DSM-III-R nicotine dependence. Multivariate multinomial logistic regression was used to model familial risk, paternal and maternal parenting behavior and substance use, sibling substance use, and friend and school peer smoking, alcohol and drug use. Ever smoking was associated with increasing offspring age, white race, high maternal pressure to succeed in school, sibling drug use, and friend smoking, alcohol and drug use. Offspring regular smoking was associated with these same factors with additional contribution from maternal ND. Offspring ND was associated with increasing offspring age, male gender, biological parents divorce, high genetic risk from father and mother ND, maternal problem drinking, maternal rule inconsistency and sibling drug use, and friend smoking, alcohol and drug use. Friend smoking had the largest magnitude of association with offspring smoking. This effect remains after accounting for familial liability and numerous parent and sibling level effects. Smoking interventions may have greatest impact by targeting smoking prevention among peer groups in adolescent and young adult populations.

Suicidal behavior, smoking, and familial vulnerability

INTRODUCTION

Smoking is a well-established correlate of suicidal behavior. It is not known if familial risk factors contribute to this association.

METHODS

Data were obtained via semistructured interviews with 1,107 twin fathers, 1,919 offspring between ages 12-32 years, and 1,023 mothers. Familial vulnerability to nicotine dependence and suicidal behavior was modeled via father and maternal self-report of these behaviors. Multinomial logistic regression models were computed with and without familial risk factors to estimate the association between offspring ever smoking, regular smoking, nicotine dependence, and a 4-level offspring suicide variable: (a) none, (b) ideation, (c) ideation + plan, and (d) ideation + plan + attempt or ideation + attempt. All models were stratified by gender and adjusted for sociodemographics, familial risk factors including parental suicidal behavior, nicotine dependence, and conduct disorder, and offspring conduct disorder, depression, alcohol abuse/dependence, and illicit drug abuse/dependence.

RESULTS

After adjusting for covariates and familial risk factors, ever smoking was not significantly associated with suicidal behavior in males and females. In males, regular smoking was associated with ideation + plan (odds ratio [OR] = 5.47; 95% CI: 1.05-28.60), and in females, regular smoking was associated with ideation + plan + attempt or ideation + attempt. In both genders, nicotine-dependent smoking was associated with ideation + plan + attempt or ideation + attempt (males: OR = 6.59; 95% CI: 1.91-22.70, females: OR = 3.37; 95% CI: 1.25-9.04). Comparison of models with and without familial risk factors indicated that there is no mediation of smoking status and suicidal behavior by familial risk.

CONCLUSIONS

Smoking and nicotine dependence are correlated with suicidal behaviour. Contributions from familial risk factors did not significantly alter this association.

Effect of paternal alcohol and drug dependence on offspring conduct disorder: gene-environment interplay

OBJECTIVE

Not only are substance-use disorders and externalizing disorders frequently comorbid, they often co-occur in families across generations. The current study examined the role of genetic and environmental influences in the relationship between paternal histories of drug dependence or alcohol dependence and offspring conduct disorder using an offspring-of-twins design.

METHOD

Participants were male twins (n = 1,774) from the Vietnam Era Twin Registry, their offspring (n = 1,917), and mothers of the offspring (n = 1,202). Twins had a history of drug dependence, alcohol dependence, or neither. Based on the father's and his co-twin's drug-dependence or alcohol-dependence history and zygosity, risk groups were constructed to reflect different levels of genetic and environmental risk that were then used to predict offspring conduct disorder.

RESULTS

After controlling for potentially confounding variables, the offspring of men with a history of drug dependence or alcohol dependence had significantly higher rates of conduct disorder, compared with offspring of men without this history. Offspring at higher genetic risk had higher rates of conduct disorder. High-risk offspring at lower environmental risk had lower rates of conduct disorder but only in the case of paternal drug-dependence risk. Lower environmental risk did not influence rates of offspring conduct disorder when the father had an alcohol-dependence history.

CONCLUSIONS

Genetic risk associated with both paternal drug-dependence and paternal alcohol-dependence histories predicted offspring conduct-disorder risk, but only risk associated with paternal drug-dependence history was mitigated by having a low-risk environment. These results demonstrated a significant gene-environment interaction effect.

Contribution of parental psychopathology to offspring smoking and nicotine dependence in a genetically informative design

OBJECTIVE

It is not known if parental psychiatric disorders have an independent effect on offspring smoking after controlling for genetic and environmental vulnerability to nicotine dependence. We tested if parental alcohol, drug, or conduct disorders; antisocial personality disorder; depression; and anxiety disorders remained significant predictors of offspring smoking initiation, regular smoking, and nicotine dependence before and after adjusting for genetic and environmental risk for nicotine dependence.

METHOD

Data were obtained via semi-structured interviews with 1,107 twin fathers, 1,919 offspring between the ages of 12 and 32, and 1,023 mothers. Genetic and environmental liability for smoking outcomes was defined by paternal and maternal nicotine dependence. Multinomial logistic regression models were computed to estimate the risk for offspring trying cigarettes, regular smoking, and the Fagerström Test for Nicotine Dependence (FTND) as a function of parental psychopathology and sociodemographics before and after adjusting for genetic and environmental vulnerability to nicotine dependence.

RESULTS

Before adjusting for genetic and environmental risk for nicotine dependence, ever trying cigarettes was associated with maternal depression, regular smoking was associated with maternal alcohol dependence and maternal conduct disorder, and FTND was associated with paternal and maternal conduct disorder and antisocial personality disorder. No parental psychopathology remained significantly associated with regular smoking and FTND after adjusting for genetic and environmental vulnerability to nicotine dependence in a multivariate model.

CONCLUSIONS

The association between parental psychopathology and offspring smoking outcomes is partly explained by genetic and environmental risk for nicotine dependence. Point estimates suggest a trend for an association between parental antisocial personality disorder and offspring regular smoking and nicotine dependence after adjusting for genetic and environmental vulnerability. Studies in larger samples are warranted.

Initial response to cigarettes predicts rate of progression to regular smoking: findings from an offspring-of-twins design

The aim of this study was to examine the association between initial subjective effects from cigarettes and the rate of progression from first cigarette to regular smoking. Latent class analysis (LCA) was applied to subjective effects data from 573 offspring of twins ranging in age from 14 to 32 years. LCA revealed four classes: 1) High on both pleasurable and physiological responses, 2) Cough only response, 3) High on physiological, low on pleasurable responses, and 4) High on pleasurable, low on physiological responses. Classes of responses were then used to predict time from first cigarette to the onset of regular smoking in a Cox proportional hazards model. Time-varying covariates representing relevant psychiatric and psychosocial factors as well as dummy variables representing the offspring-of-twins design were included in the model. Members of classes 1 and 4 transitioned more rapidly to regular smoking than the classes characterized as low on the pleasurable response dimension. Our findings provide evidence that previously reported associations between pleasurable initial experiences and progression to regular smoking hold true as well for the rate at which that transition occurs. Furthermore, the fact that profiles of responses did not fall into global categories of exclusively pleasurable vs. exclusively negative (physiological) responses suggests the importance of considering both dimensions in combination to characterize risk for smoking-related outcomes.

Genetic and environmental influences on cannabis use initiation and problematic use: a meta-analysis of twin studies

BACKGROUND

Because cannabis use is associated with social, physical and psychological problems, it is important to know what causes some individuals to initiate cannabis use and a subset of those to become problematic users. Previous twin studies found evidence for both genetic and environmental influences on vulnerability, but due to considerable variation in the results it is difficult to draw clear conclusions regarding the relative magnitude of these influences.

METHODS

A systematic literature search identified 28 twin studies on cannabis use initiation and 24 studies on problematic cannabis use. The proportion of total variance accounted for by genes (A), shared environment (C) and unshared environment (E) in (i) initiation of cannabis use and (ii) problematic cannabis use was calculated by averaging corresponding A, C and E estimates across studies from independent cohorts and weighting by sample size.

RESULTS

For cannabis use initiation, A, C and E estimates were 48%, 25% and 27% in males and 40%, 39% and 21% in females. For problematic cannabis use A, C and E estimates were 51%, 20% and 29% for males and 59%, 15% and 26% for females. Confidence intervals of these estimates are considerably narrower than those in the source studies.

CONCLUSIONS

Our results indicate that vulnerability to both cannabis use initiation and problematic use was influenced significantly by A, C and E. There was a trend for a greater C and lesser A component for cannabis use initiation compared to problematic use for females.

Testing the equal environments assumption in the Children of Twins design

In a Children of Twins (COT) design, the environmental and genetic risk of a child is, in part, dependent upon the status of the father and the father's cotwin. The logic of the COT method breaks down if the zygosity of the twin pair is confounded with the environment provided to the child (a version of the Equal Environment Assumption, EEA). If MZ twin fathers see each other more often than DZ twin fathers, and a child's uncle is the affected twin in discordant pairs, this could increase the environmental risk of children of MZ over that of DZ discordant twins. The current study was designed to test the EEA in the COT design, specifically in children of alcohol and drug dependent fathers. Results indicated that MZ twins did have more contact than DZ twins. Regression analyses were conducted to predict child externalizing symptom counts from father's zygosity group status, level of contact with father's cotwin, and their interaction. Results found no significant interaction between father's zygosity and the higher level of cotwin contact (seen in MZ twins) in predicting several measures of offspring externalizing risk. The results of this study suggested that the COT design does not confound zygosity with differences in environmental risk exposure, findings that support the validity of the EEA within this research context.

Externalizing behavior problems and cigarette smoking as predictors of cannabis use: the TRAILS Study

OBJECTIVE

To examine externalizing behavior problems and cigarette smoking as predictors of subsequent cannabis use.

METHOD

Dutch adolescents (N = 1,606; 854 girls and 752 boys) from the TRacking Adolescents' Individual Lives Survey (TRAILS) ongoing longitudinal study were examined at baseline (ages 10-12 [T1]) and at two follow-up assessments (ages 12-15 [T2] and 15-18 [T3]). The analysis focused on DSM-IV externalizing behavior (conduct, attention deficit hyperactivity, and oppositional) problems at T1, assessed by the Youth Self Report and the Child Behavior Check List, on self-reported ever smoking at T2, and on cannabis use at T3.

RESULTS

All associations of parent-rated externalizing behavior problems with cannabis were mediated by earlier smoking. Considering self-reported problems, none of these associations with cannabis were mediated by smoking, except the influence of self-reported conduct problems in girls. Interestingly, even after adjusting for externalizing problems, earlier smoking independently and consistently predicted cannabis use. The adjusted odds ratios for smoking varied in boys from 4.8 to 5.2 (ever) from 10 to 12 (daily) and from 22 to 23 (early-onset) whereas in girls from 4.9 to 5.0, 5.6 to 6.1, and 27 to 28, respectively (p <.001 for all).

CONCLUSIONS

Our findings challenge the view that externalizing behavior problems directly predict cannabis initiation. Such associations were inconsistent across informants and sexes and were often mediated by earlier smoking. Early smoking onset is a powerful predictor of later cannabis initiation independent of preceding externalizing behavior problems. Although externalizing behavior problems are important as a starting point for substance use trajectories, early-onset smoking should be identified as an important marker of cannabis use risk.

Subjective effects to cannabis are associated with use, abuse and dependence after adjusting for genetic and environmental influences

BACKGROUND

Previous reports in adults have suggested that the effects experienced after cannabis use can be described in terms of positive and negative subtypes that are heritable and are associated with abuse and dependence. This study extends existing research by inclusion of adolescents and young adults in an offspring of twins design which makes it possible to take into account genetic and environmental risks for substance use disorder.

METHODS

Data were collected from 725 twin members of the Vietnam Era Twin Registry, 839 of their 12-32 year old biological offspring and 427 mothers. Offspring who had ever used cannabis (n=464) were asked the degree to which they typically experienced 13 subjective effects shortly after using cannabis. Latent class analysis (LCA) was used to derive subjective effect classes and logistic regression models were computed to test associations between subjective effect class and heavy cannabis use, abuse and dependence after adjusting for familial risk and psychopathology and sociodemographics.

RESULTS

The best fitting LCA model included 4 classes of responders which were characterized as 'high responders' (39%), 'positive responders' (28%), 'mixed/relaxed' (22%), and 'low responders' (11%). Compared to low responders, members of other classes were heavier users (OR range 3.0-11.8). Compared to mixed/relaxed responders and positive responders, high responders were more likely to have cannabis abuse and dependence.

CONCLUSIONS

Subjective reactions to cannabis use are associated with use to heavy use, abuse and dependence in adolescents and young adults. This association exists above and beyond the genetic vulnerability for problem cannabis use.