Evidence for Sex Convergence in Prevalence of Cannabis Use: A Systematic Review and Meta-Regression.

OBJECTIVE: Generally, cannabis use has been more prevalent in men than in women. However, emerging evidence suggests that the prevalence of cannabis use is converging among males and females from recent cohorts. This study aimed to systematically summarize published literature on birth cohort changes in male-to-female ratios in prevalence of cannabis use. METHOD: Twenty-two studies with a median sample size of 85,052 were identified for inclusion. Data were collected between 1979 and 2010, representing birth cohorts from 1936 to 1999. For quantitative synthesis, male-to-female ratios in prevalence of any cannabis use were calculated for all 5-year birth cohorts available, generating 348 separate ratios among birth cohorts from 1941 to 1995 in 30 countries. Random-effects meta-analyses generated pooled sex ratios, stratified by 5-year birth cohorts. RESULTS: Of the 22 included studies, 10 reported some evidence of sex convergence in cannabis use among more recent cohorts. Quantitative synthesis found that the ratio of cannabis use prevalence in males and females decreased significantly from 2.0 among cohorts born in 1941 to 1.3 among those born in 1995. CONCLUSIONS: Findings support the narrowing sex gap in the prevalence of cannabis use. Results are concordant with a broader literature demonstrating sex convergence in prevalence of other substance use, particularly alcohol use and related harms. Both young women and men should be the target of prevention and early intervention efforts. Future research in more diverse global settings, especially in low- and middle-income countries, would enhance the international scope of the findings.

A prospective study of the substance use and mental health outcomes of young adult former and current cannabis users.

INTRODUCTION AND AIMS: The extent to which young adult former cannabis users fare better than infrequent users is unclear. We investigated the association between cannabis use status at age 23 and substance use and mental health outcomes at age 27. DESIGN AND METHODS: Data were from the 20+ year cohort of the PATH Through Life Study. Lifetime cannabis users (n = 1410) at age 23 were classified as former/occasional/regular users. Multivariable logistic regression was used to estimate the association between cannabis use status at age 23 and six outcomes assessed at age 27. RESULTS: Compared with occasional cannabis users: (i) former users had odds of subsequent tobacco use [odds ratio (OR) = 0.67, 95% confidence interval (CI) 0.52-0.85], illicit drug use (cannabis, OR = 0.22, 95% CI 0.17-0.28; other illicit drugs, OR = 0.29, 95% CI 0.22-0.39) and mental health impairment (OR = 0.71, 95% CI 0.55-0.92) that were 29-78% lower; and (ii) regular users had odds of subsequent frequent alcohol use (OR = 2.34, 95% CI 0.67-1.34), tobacco use (OR = 3.67, 95% CI 2.54-5.30), cannabis use (OR = 11.73, 95% CI 6.81-20.21) and dependence symptoms (OR = 12.60, 95% CI 8.38-18.94), and other illicit drug use (OR = 2.95, 95% CI 2.07-4.21) that were 2-13 times greater. Associations attenuated after covariate adjustment, and most remained significant. DISCUSSION AND CONCLUSIONS: Clear associations exist between cannabis use status in young adulthood and subsequent mental health and substance use. While early intervention remains important to prevent regular cannabis use and the associated harms, experimentation with cannabis use in the years leading into young adulthood may not necessarily determine an immutable pathway to mental health problems and illicit substance use. [Silins E, Swift W, Slade T, Toson B, Rodgers B, Hutchinson DM. A prospective study of the substance use and mental health outcomes of young adult former and current cannabis users. Drug Alcohol Rev 2017;00:000-000].

Adolescent Predictors of a Typology of DSM-5 Alcohol Use Disorder Symptoms in Young Adults Derived by Latent Class Analysis Using Data From an Australian Cohort Study.

OBJECTIVE: There is little research examining alcohol use disorder (AUD) symptoms (based on criteria from the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition [DSM-5]) in young adulthood. We assessed symptom structure at 24 years using latent class analysis (LCA), examining relationships between class membership and (a) concurrent alcohol use and DSM-5 AUD severity and (b) adolescent risk factors. METHOD: A stratified, random sample of 1,943 adolescents ages 14-15 years was recruited from 44 secondary schools in Victoria, Australia, and interviewed during adolescence and young adulthood. We report findings on drinkers who completed the AUD module (N = 1,268; 51% male). RESULTS: Data clearly fit a three-class, dimensional model, comprising "mild symptoms" (63.2%), "moderate symptoms" (32.2%), and "severe symptoms" (4.6%) classes. Class membership was validated by concurrent drinking patterns and in reasonable agreement with DSM-5 AUD severity categories. Relative to mild symptoms class membership, moderate symptoms class membership increased odds of adolescent alcohol problems (odds ratio [OR] = 2.0, 95% CI [1.2, 3.5]) and persisting anxiety/depression symptoms (OR = 1.9, 95% CI [1.2, 3.1]). Daily smoking (OR = 2.6, 95% CI [1.1, 5.9]), persisting anxiety/ depression symptoms (OR = 2.5, 95% CI [1.3, 5.0]), and antisocial behavior (OR = 3.2, 95% CI [1.5, 6.8]) increased odds of severe symptoms class membership. Adolescent daily smoking (OR = 0.3, 95% CI [0.11, 0.81]) and antisocial behavior (OR = 0.3, 95% CI [0.14, 0.64]) were less likely among members of the moderate symptoms class, relative to the severe symptoms class. CONCLUSIONS: We found support for a dimensional AUD typology like that in DSM-5. Young adults with more severe AUD symptoms had a different adolescent risk profile than those in the low and moderate classes. These findings provide a focus for preventive intervention in adolescence to limit the severity of AUDs in young adulthood.

Factors associated with variability and stability of cannabis use in young adulthood.

BACKGROUND: This study investigated the factors associated with initiating cannabis use, reverting to cannabis use and remaining a cannabis user in young adulthood. This is an important area of research as the risk for cannabis initiation is extending beyond adolescence and opportunities to influence cannabis use pathways can emerge throughout the life-course. METHODS: A large, community-based sample was followed prospectively. Data from two successive waves (mean age 23 years and 27 years respectively) of the Path Through Life Study (PATH) were analysed (n=2045). The longitudinal design enabled change in cannabis use in young adulthood to be predicted based on factors assessed approximately four years prior. RESULTS: An environment of licit drug use was strongly associated with initiating cannabis use (tobacco: OR=4.98, 95%CI: 2.31-10.76) and reverting to cannabis use in young adulthood (alcohol: OR=2.13, 95%CI: 1.42-3.19). Greater fun seeking was found to orientate people towards initiating cannabis use in young adulthood (OR=1.17, 95%CI: 1.04-1.30). Higher psychoticism increased the odds of remaining a cannabis user (OR=1.19, 95%CI: 1.07-1.33). Religious involvement was protective of cannabis initiation (OR=0.89, 95%CI: 0.83-0.95). Early childhood factors did not influence the pattern of cannabis use in young adulthood. CONCLUSIONS: The findings make an important contribution to the development of prevention and intervention strategies for young adults by drawing attention to specific areas of risk and protection.

Changes in cannabis use among young people: impact on mental health.

PURPOSE OF REVIEW: The aim of this review was to examine current trends in cannabis use and cannabis use disorder (CUD) among youth, and to investigate recent findings concerning the relationship between cannabis use and mental health concerns, with a focus on how use during adolescence may interact with related mental health disorders. RECENT FINDINGS: Current data indicate that cannabis use among adolescents has shown both marginal increases and decreases, depending on global location; however, the profile of cannabinoids in cannabis may now be biased toward those that promote psychotogenic and memory-impairing effects. CUD has been found most prevalent among youth. After controlling for multiple confounders, longitudinal research suggests that cannabis use predicts the development of anxiety disorders, depression, suicidal ideation, certain personality disorders, and interpersonal violence. Further, associations have been found stronger in adolescents relative to adults, and younger age of initiation increases the risk of developing mental health disorders. SUMMARY: Cannabis use among youth remains prevalent, and recent studies are consolidating previous findings that adolescents are especially vulnerable to mental health disorders associated with cannabis. This suggests that cannabis involvement requires increased prominence in research, prevention initiatives, routine screening, and interventions to improve adolescent mental health.

Health outcomes associated with long-term regular cannabis and tobacco smoking.

This study aimed to identify patterns of health concerns associated with long-term use of cannabis and tobacco individually, as well as in combination. We recruited 350 adults aged 40 or over who smoked cannabis but not tobacco (cannabis-only group, n=59), smoked both cannabis and tobacco (cannabis/tobacco group, n=88), smoked tobacco but not cannabis (tobacco-only group, n=80), or used neither substance (control group, n=123). Participants completed a survey addressing substance use, diagnosed medical conditions, health concerns relating to smoking cannabis/tobacco, and general health (measured using the Physical Health Questionnaire and the Short Form 36). Several significant differences were found among the four groups. With regard to diagnosed medical conditions, the three smoking groups reported significantly higher rates of emphysema than did the control group (ps<.001). However, all members of the cannabis-only group diagnosed with emphysema were former regular tobacco smokers. Total general health scores, general health subscales, and items addressing smoking-related health concerns also revealed several significant group differences, and these tended to show worse outcomes for the two tobacco smoking groups. Findings suggest that using tobacco on its own and mixing it with cannabis may lead to worse physical health outcomes than using cannabis alone.

The persistence of the association between adolescent cannabis use and common mental disorders into young adulthood.

AIMS: Debate continues about whether the association between cannabis use in adolescence and common mental disorders is causal. Most reports have focused on associations in adolescence, with few studies extending into adulthood. We examine the association from adolescence until the age of 29 years in a representative prospective cohort of young Australians. DESIGN: Nine-wave, 15-year representative longitudinal cohort study, with six waves of data collection in adolescence (mean age 14.9-17.4 years) and three in young adulthood (mean age 20.7, 24.1 and 29.1 years). PARTICIPANTS: Participants were a cohort of 1943 recruited in secondary school and surveyed at each wave when possible from mid-teen age to their late 20s. SETTING: Victoria, Australia. MEASUREMENTS: Psychiatric morbidity was assessed with the Revised Clinical Interview Schedule (CIS-R) at each adolescent wave, and as Composite International Diagnostic Interview (CIDI)-defined ICD-10 major depressive episode and anxiety disorder at 29 years. Frequency of cannabis use was measured in the past 6 months in adolescence. Cannabis use frequency in the last year and DSM-IV cannabis dependence were assessed at 29 years. Cross-sectional and prospective associations of these outcomes with cannabis use and dependence were estimated as odds ratios (OR), using multivariable logistic regression models, with the outcomes of interest, major depressive episode (MDE) and anxiety disorder (AD) at 29 years. FINDINGS: There were no consistent associations between adolescent cannabis use and depression at age 29 years. Daily cannabis use was associated with anxiety disorder at 29 years [adjusted OR 2.5, 95% confidence interval (CI):< 1.2-5.2], as was cannabis dependence (adjusted OR 2.2, 95% CI: 1.1-4.4). Among weekly+ adolescent cannabis users, those who continued to use cannabis use daily at 29 years remained at significantly increased odds of anxiety disorder (adjusted OR 3.2, 95% CI: 1.1-9.2). CONCLUSIONS: Regular (particularly daily) adolescent cannabis use is associated consistently with anxiety, but not depressive disorder, in adolescence and late young adulthood, even among regular users who then cease using the drug. It is possible that early cannabis exposure causes enduring mental health risks in the general cannabis-using adolescent population.

The perceived health risks of cannabis use in an Australian household survey.

INTRODUCTION AND AIMS: Perceived risks of cannabis use have rarely been researched in Australia. This paper reports on the beliefs about the adverse effects of cannabis use on health, social well-being, driving, mental health and changes in cannabis over time. DESIGN AND METHODS: Survey of 918 Australian adults was conducted as part of a quarterly omnibus self-report survey of an established panel. RESULTS: Respondents believed that cannabis use can cause health and social problems, can adversely affect a person's ability to drive a car, can be addictive, and can lead to use of other illicit drugs. They were uncertain as to whether cannabis can cause schizophrenia and depression, and whether cannabis had become more potent over time. IMPLICATIONS: Prevention efforts should focus on educating the Australian people about the nature of cannabis-related harms.

Cannabis and progression to other substance use in young adults: findings from a 13-year prospective population-based study.

BACKGROUND: Adolescent cannabis use predicts the onset of later illicit drug use. In contrast, little is known about whether cannabis in young adulthood also predicts subsequent progression or cessation of licit or illicit drug use. METHODS: 13-year longitudinal cohort study with recruitment in secondary school students in Victoria, Australia. There were six waves of adolescent data collection (mean age 14.9-17.4 years) followed by three in young adulthood (mean age 20.7, 24.1 and 29.0 years). Discrete-time proportional hazards models were used to assess predictive associations between cannabis use frequency (occasional (

Outcomes of occasional cannabis use in adolescence: 10-year follow-up study in Victoria, Australia.

BACKGROUND: Regular adolescent cannabis use predicts a range of later drug use and psychosocial problems. Little is known about whether occasional cannabis use carries similar risks. AIMS: To examine associations between occasional cannabis use during adolescence and psychosocial and drug use outcomes in young adulthood; and modification of these associations according to the trajectory of cannabis use between adolescence and age 20 years, and other potential risk factors. METHOD: A 10-year eight-wave cohort study of a representative sample of 1943 secondary school students followed from 14.9 years to 24 years. RESULTS: Occasional adolescent cannabis users who continued occasional use into early adulthood had higher risks of later alcohol and tobacco dependence and illicit drug use, as well as being less likely to complete a post-secondary qualification than non-users. Those using cannabis at least weekly either during adolescence or at age 20 were at highest risk of drug use problems in young adulthood. Adjustment for smoking in adolescence reduced the association with later educational achievement, but associations with drug use problems remained. CONCLUSIONS: Occasional adolescent cannabis use predicts later drug use and educational problems. Partial mediation by tobacco use raises a possibility that differential peer affiliation may play a role.

Adolescent cannabis users at 24 years: trajectories to regular weekly use and dependence in young adulthood.

AIMS: To examine the association between cannabis use by 18 years and problematic cannabis use at 24 years, considering possible mediating and confounding factors. DESIGN: Ten-year representative prospective study with data from six time-points in adolescence (mean age 14.9-17.4 years) and two in young adulthood (mean age 20.7 and 24.1 years) SETTING: Victoria, Australia. PARTICIPANTS: Inception cohort of 1943 secondary school students (95.6% response rate), with 1520 (78% of adolescent participants) interviewed in the final wave. MEASUREMENTS: Participants reported frequency of cannabis use for the past 6 months at each time-point in adolescence (age 14-17 years). Cannabis exposure was defined as: maximum frequency of use (occasional, weekly, daily), number of waves of use (1 or 2; 3-6) and first wave of use (early use: first waves 1-3). Young adult (24 years) outcomes were: weekly+ cannabis use and DSM-IV cannabis dependence, referred to collectively as problematic use. FINDINGS: Of those interviewed at age 24 (wave 8), 34% had reported cannabis use in adolescence (waves 1-6), 12% at a level of weekly or more frequent use; 37% of these adolescent cannabis users were using at least weekly at wave 8, with 20% exhibiting dependence. Persistent adolescent cannabis and tobacco use as well as persistent mental health problems were associated strongly with problematic cannabis use at 24 years, after adjustment for potential confounding factors. CONCLUSIONS: Heavy, persistent and early-onset cannabis use were all strongly predictive of later cannabis problems. Even so, occasional use was not free of later problems. Where there was co-occurring tobacco use or persistent mental health problems, risks for later problem cannabis use was higher.

Correlates of driving under the influence of cannabis.

BACKGROUND: Identifying cannabis users who are most at risk of driving under the influence of cannabis (DUIC) has important implications for drug treatment and prevention efforts. This paper examined correlates of DUIC among a purposive sample of recent cannabis users. METHODS: Interviews were carried out among a cross-sectional sample of 320 Australian cannabis users. Past-year prevalence of DUIC (without using alcohol or other drugs) was regressed against a range of potential predictor variables. RESULTS: Use of multiple drugs, believing that DUIC does not increase accident risk and cannabis dependence all predicted likelihood of DUIC. There was an interaction between age of first cannabis use and gender, whereby earlier onset cannabis use predicted DUIC but only among women. CONCLUSIONS: The correlates of drug driving reflected cannabis users' beliefs about the dangers of cannabis use as well as their patterns of drug consumption. The emergence of cannabis dependence and age of onset as predictors of DUIC suggests a clearly defined role for treatment and prevention efforts in reducing the potential harms associated with DUIC.

Preventing cannabis users from driving under the influence of cannabis.

Face-to-face, structured interviews were conducted with 320 recent cannabis users in New South Wales, Australia to assess the likely deterrent effects of (a) increasing the certainty of apprehension for driving under the influence of cannabis (DUIC) and (b) doubling the severity of penalties for DUIC. Participants were presented with a drug-driving scenario and asked to indicate their likelihood of driving given that scenario. The perceived risk of apprehension and severity of punishment were manipulated in each scenario to create four different certainty/severity conditions and participants were randomly allocated to one of these four groups. A subsidiary aim was to assess the likely impact of providing factual information about the accident risk associated with DUIC. Recent drug drivers who felt at low risk of accident when DUIC were asked to rate their willingness to drive if convinced that it was dangerous. The results suggested that increasing the certainty but not severity of punishment would produce reductions in cannabis-intoxicated driving among recent cannabis users. Providing factual information about the risks associated with DUIC would appear to have little impact on drug-driving rates among this population.

The Adolescent Cannabis Check-Up: feasibility of a brief intervention for young cannabis users.

In this study, we assessed the feasibility and effectiveness of the Adolescent Cannabis Check-Up (ACCU), a brief intervention for young cannabis users. For this initial feasibility study, we used an uncontrolled pre-test/post-test design. Participants were cannabis users aged between 14 and 19 years (n = 73) and concerned parents (n = 69). The intervention comprised an individual assessment session followed 1 week later by a session of personalized feedback delivered in a motivational interviewing style. An optional third session that focused on skills and strategies for making behavioral change was offered. Of the entire sample of cannabis users, 78% reported voluntarily reducing or stopping their cannabis use during the 90 days to follow-up and 16.7% reported total abstinence during this time. In addition, significant reductions were found on measures of both quantity and frequency of use and dependence. These reductions were maintained at 6-month follow-up. Clearly, these preliminary findings must be interpreted with caution given the study design and absence of a control group. The ACCU was, however, able to attract and retain young cannabis users who were not necessarily interested in change. The approach was acceptable to young people and associated with reductions in cannabis use. It appears to be a model that warrants further research in early and brief interventions for this population.