Common Genetic Contributions to Alcohol and Cannabis Use and Dependence Symptomatology

Background: Despite mounting evidence that use of and dependence on alcohol and cannabis are influenced by heritable factors, the extent to which heritable influences on these phenotypes overlap across the 2 substances has only rarely been explored. In the current study, we quantified cross‐substance overlap in sources of variance and estimated the degree to which within‐substance associations between use and dependence measures are attributable to common genetic and environmental factors for alcohol and cannabis. Methods: The sample was comprised of 6,257 individuals (2,761 complete twin pairs and 735 singletons) from the Australian Twin Registry, aged 24 to 36 years. Alcohol and cannabis use histories were collected via telephone diagnostic interviews and used to derive an alcohol consumption factor, a frequency measure for cannabis use, and DSM‐IV alcohol and cannabis dependence symptom counts. Standard genetic analyses were conducted to produce a quadrivariate model that provided estimates of overlap in genetic and environmental influences across the 4 phenotypes. Results: Over 60% of variance in alcohol consumption, cannabis use, and cannabis dependence symptoms, and just under 50% of variance in alcohol dependence (AD) symptoms were attributable to genetic sources. Shared environmental factors did not contribute significantly to the 4 phenotypes. Nearly complete overlap in heritable influences was observed for within‐substance measures of use and dependence symptoms. Genetic correlations across substances were 0.68 and 0.62 for use and dependence symptoms, respectively. Conclusions: Common heritable influences were evident for alcohol and cannabis use and for AD and cannabis dependence symptomatology, but findings indicate that substance‐specific influences account for the majority of the genetic variance in the cannabis use and dependence phenotypes. By contrast, the substantial correlations between alcohol use and AD symptoms and between cannabis use and cannabis dependence symptoms suggest that measures of heaviness of use capture much of the same genetic liability to alcohol‐ and cannabis‐related problems as dependence symptomatology.     

Explaining associations between cannabis use disorders in adolescence and later major depression: a test of the psychosocial failure model

Aims

Cannabis use disorders (CUDs) in adolescence are associated with increased risk for later major depressive disorder (MDD). The goal of this study was to examine the “psychosocial failure” explanation for this association: the possibility that psychosocial consequences of CUDs in adolescence account for the increased risk for later MDD.

Methods

Participants (n = 1252) were drawn from the community-based sample of the Minnesota Twin Family Study and were assessed at ages 17, 20, and 24. CUDs and MDD were assessed via structured interview. “Psychosocial failure” was defined as educational failure (high school dropout), occupational failure (persistent unemployment), or engagement in crime.

Results

Psychosocial failure partially mediated the association between CUDs in adolescence and later MDD.

Conclusions

The adverse psychosocial consequences of CUDs in adolescence partially – but not fully – account for the observed association between early CUDs and later MDD.     

Validation of the Cannabis Expectancy Questionnaire (CEQ) in adult cannabis users in treatment

Background

Outcome expectancies are a key cognitive construct in the etiology, assessment and treatment of Substance Use Disorders. There is a research and clinical need for a cannabis expectancy measure validated in a clinical sample of cannabis users.

Method

The Cannabis Expectancy Questionnaire (CEQ) was subjected to exploratory (n = 501, mean age 27.45, 78% male) and confirmatory (n = 505, mean age 27.69, 78% male) factor analysis in two separate samples of cannabis users attending an outpatient cannabis treatment program. Weekly cannabis consumption was clinically assessed and patients completed the Severity of Dependence Scale-Cannabis (SDS-C) and the General Health Questionnaire (GHQ-28).

Results

Two factors representing Negative Cannabis Expectancies and Positive Cannabis Expectancies were identified. These provided a robust statistical and conceptual fit for the data. Internal reliabilities were high. Negative expectancies were associated with greater dependence severity (as measured by the SDS) and positive expectancies with higher consumption. The interaction of positive and negative expectancies was consistently significantly associated with self-reported functioning across all four GHQ-28 scales (Somatic Concerns, Anxiety, Social Dysfunction and Depression). Specifically, within the context of high positive cannabis expectancy, higher negative expectancy was predictive of more impaired functioning. By contrast, within the context of low positive cannabis expectancy, higher negative expectancy was predictive of better functioning.

Conclusions

The CEQ is the first cannabis expectancy measure to be validated in a sample of cannabis users in treatment. Negative and positive cannabis expectancy domains were uniquely associated with consumption, dependence severity and self-reported mental health functioning.     

A comparison of the symptoms and short-term clinical course in inpatients with substance-induced psychosis and primary psychosis

Relatively little is known about the clinical course of symptoms in patients with a substance-induced psychosis (SIP) compared with those with a primary psychotic disorder (PPD). In this study, symptoms associated with psychosis were monitored across admission in two groups of patients: those with SIP (amphetamines or cannabis; n = 47) and those with PPD (n = 51). Sixty-two percent of patients were first admissions, 23% had one previous admission, and a further 14% had had two previous admissions. Symptoms were monitored using the Brief Psychiatric Rating Scale. Scores on the positive symptoms scale, negative symptoms scale, manic excitement, and negative mood were reported as was the extent of observed disturbed behavior at admission and then at Days 4/5, 8/9, 15/16, 22/23, 29/30, 36/37, 43/44, and 50/51. Patients with a SIP experienced more severe mania and disturbed behavior at admission than those with a PPD. However, these symptoms abated more rapidly for the SIP group during admission. Although positive symptom scores were equally high at admission for both groups, there was a more rapid abatement of these symptoms in the SIP group. Finally, negative symptoms were lower in the SIP group at admission and at Days 50/51, although the decline in symptoms was comparable in both groups.     

The impact of comorbid cannabis and methamphetamine use on mental health among regular ecstasy users

Objective

Residual effects of ecstasy use induce neurotransmitter changes that make it biologically plausible that extended use of the drug may induce psychological distress. However, there has been only mixed support for this in the literature. The presence of polysubstance use is a confounding factor. The aim of this study was to investigate whether regular cannabis and/or regular methamphetamine use confers additional risk of poor mental health and high levels of psychological distress, beyond regular ecstasy use alone.

Method

Three years of data from a yearly, cross-sectional, quantitative survey of Australian regular ecstasy users was examined. Participants were divided into four groups according to whether they regularly (at least monthly) used ecstasy only (n = 936), ecstasy and weekly cannabis (n = 697), ecstasy and weekly methamphetamine (n = 108) or ecstasy, weekly cannabis and weekly methamphetamine (n = 180). Self-reported mental health problems and Kessler Psychological Distress Scale (K10) were examined.

Results

Approximately one-fifth of participants self-reported at least one mental health problem, most commonly depression and anxiety. The addition of regular cannabis and/or methamphetamine use substantially increases the likelihood of self-reported mental health problems, particularly with regard to paranoia, over regular ecstasy use alone. Regular cannabis use remained significantly associated with self reported mental health problems even when other differences between groups were accounted for. Regular cannabis and methamphetamine use was also associated with earlier initiation to ecstasy use.

Conclusions

These findings suggest that patterns of drug use can help identify at risk groups that could benefit from targeted approaches in education and interventions. Given that early initiation to substance use was more common in those with regular cannabis and methamphetamine use and given that this group had a higher likelihood of mental health problems, work around delaying onset of initiation should continue to be a priority.     

Psychometric properties of the CAST and SDS scales in young adult cannabis users

Aim

To assess the validity of two cannabis use severity scales among young cannabis users and to evaluate their ability to detect Substance Use Disorders (SUD).

Participants

241 volunteers (18–25 years), with a wide spectrum of cannabis use in the last 12 months.

Measurements

The Cannabis Abuse Screening Test (CAST) and Severity of Dependence Scale (SDS) were self-administered. The Psychiatric Interview for Substance and Mental Disorders (PRISM) was used as gold standard for cannabis use disorders according to DSM-IV. Reliability and validity were assessed for two different CAST coding algorithms (b—binary and f—full) and for the SDS. In addition, the cannabis use diagnostic criteria contained in the PRISM were grouped to approximate forthcoming proposed DSM-V criteria to further evaluate these scales.

Findings

26.6% (95% CI: 21.0–32.2) of the subjects met criteria for cannabis dependence, and 49.0% (95% CI: 42.7–55.3) for cannabis use disorders. For both scales internal consistency (Cronbach's alpha > 0.71) and test–retest intraclass correlation coefficients (> 0.80) were good. The score 12 in the CAST-full discriminated better than others between presence and absence of dependence (27.0%; 95% CI: 21.4–32.6) while the score for discrimination of SUD was 9 (51.5%; 95% CI: 45.1–57.8). For the SDS the values were 7 (22.0%; 95% CI: 16.8–27.2) and 3 (64.7%; 95% CI: 58.7–70.8), respectively. According to proposed DSM-V criteria, for moderate and severe addiction the values for the CAST-f were 7 (68.5%; 95% CI: 62.5–74.3) and 12 (27%; 95% CI: 21.3–32.6) and for the SDS, 3 (65.0%; 95% CI: 58.7–70.8) and 7 (22%; 95% CI: 17.0–34.3), respectively.

Conclusions

The CAST and SDS applied to young cannabis users are reliable and valid measures to detect cannabis use disorders when compared to both DSM-IV and proposed DSM-V criteria.     

Cannabis-related impairment and social anxiety: the roles of gender and cannabis use motives

Social anxiety appears to be especially related to cannabis-related problems, yet the nature of this association remains unclear. Some data suggest that socially anxious men may be especially vulnerable to problematic cannabis use. The current study examined the relations between social anxiety, cannabis use and use-related problems, and motives for cannabis use by gender among 174 (42.5% female) current (past-month) cannabis users. Among men, social anxiety was significantly, positively related to the number of cannabis-related problems and coping and conformity motives. Coping and conformity motives mediated the relation between social anxiety and cannabis-related problems. Among women, social anxiety was significantly related only to social motives, and was unrelated to cannabis-related problems. These findings suggest that socially anxious men may be especially vulnerable to using cannabis as a means of avoidance coping (avoiding scrutiny and negative affect), which may contribute to the high rates of cannabis-related problems among socially anxious individuals.     

Tobacco, alcohol, cannabis and other illegal drug use among young adults: the socioeconomic context

Background

Low socioeconomic position predicts risk of substance abuse, yet few studies tested the role of preexisting familial and individual characteristics.

Methods

Data come from the TEMPO (Trajectoires Epidémiologiques en Population) study (community sample in France, 1991–2009, n = 1103, 22–35 years in 2009) set up among offspring of participants of an epidemiological study (GAZEL). Past 12-month substance use was assessed in 2009 by self-completed mail survey: regular tobacco smoking, alcohol abuse (AUDIT), cannabis use, problematic cannabis use (CAST), other illegal drug use. Socioeconomic position was defined by educational attainment, occupational grade, employment stability and unemployment. Covariates included demographics (age, sex, relationship status, parenthood), family background (parental income, parental tobacco smoking, parental alcohol use), and juvenile characteristics (psychological problems, academic difficulties) measured longitudinally.

Results

35.8% of study participants were regular smokers, 14.3% abused alcohol, 22.6% used cannabis (6.3% had problematic cannabis use) and 4.1% used other illegal drugs. Except for alcohol abuse, substance use rates were systematically higher in individuals with low, rather than intermediate/high, socioeconomic position (age and sex-adjusted ORs from 1.75 for cannabis use to 2.11 for tobacco smoking and 2.44 for problematic cannabis use). In multivariate analyses these socioeconomic disparities were decreased, but remained statistically significant (except for illegal drugs other than cannabis).

Conclusions

Tobacco smoking, alcohol, cannabis and polysubstance use are common behaviors among young adults, particularly those experiencing socioeconomic disadvantage. Interventions aiming to decrease substance abuse and reduce socioeconomic inequalities in this area should be implemented early in life.     

Quantifying cannabis use with the Timeline Followback approach: A psychometric evaluation

Background

In the absence of a standardized cannabis unit, self-report instruments are inadequate for accurate quantification of cannabis use. The study extends the feasibility of using a cannabis substitute to reliably and validly measure quantity of cannabis use.

Method

Ninety-eight adult Australian cannabis users (M age = 27.98, SD = 11.10; 65.31% male) completed a 90-day Timeline Followback interview regarding their cannabis use, utilizing the cannabis substitute Marijuanilla to report on quantity of use. Ninety-two of these individuals completed the interview at two time-points, and 56 of these participants had collaterals corroborate their cannabis use reports.

Results

Inter-rater reliability was excellent, while test–retest reliability was good to excellent. Intra-class correlation coefficients between participant and collateral reports, while similar to previous research, were unacceptable. Quantity of cannabis use statistically significantly added to frequency of use in predicting cannabis problems and dependence severity. Concurrent and discriminant validity were established with single-item and positive impression management measures, respectively. In addition, Marijuanilla appeared similar to one specimen of street seized cannabis, but not to two others. Importantly, participants’ cravings to use cannabis did not increase as a result of using the cannabis substitute to report on their cannabis use.

Conclusions

These data suggest that utilizing Marijuanilla to facilitate the reporting of grams of cannabis use may be reliable and valid; however, such comprehensive assessment may only be necessary for clinical trials and epidemiological studies, which rely on precise estimates of cannabis use.