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 substance use and educational attainment: An integrative data analysis comparing cannabis and alcohol from three Australasian cohorts.

BACKGROUND: The relative contributions of cannabis and alcohol use to educational outcomes are unclear. We examined the extent to which adolescent cannabis or alcohol use predicts educational attainment in emerging adulthood. METHODS: Participant-level data were integrated from three longitudinal studies from Australia and New Zealand (Australian Temperament Project, Christchurch Health and Development Study, and Victorian Adolescent Health Cohort Study). The number of participants varied by analysis (N=2179-3678) and were assessed on multiple occasions between ages 13 and 25. We described the association between frequency of cannabis or alcohol use prior to age 17 and high school non-completion, university non-enrolment, and degree non-attainment by age 25. Two other measures of alcohol use in adolescence were also examined. RESULTS: After covariate adjustment using a propensity score approach, adolescent cannabis use (weekly+) was associated with 1½ to two-fold increases in the odds of high school non-completion (OR=1.60, 95% CI=1.09-2.35), university non-enrolment (OR=1.51, 95% CI=1.06-2.13), and degree non-attainment (OR=1.96, 95% CI=1.36-2.81). In contrast, adjusted associations for all measures of adolescent alcohol use were inconsistent and weaker. Attributable risk estimates indicated adolescent cannabis use accounted for a greater proportion of the overall rate of non-progression with formal education than adolescent alcohol use. CONCLUSIONS: Findings are important to the debate about the relative harms of cannabis and alcohol use. Adolescent cannabis use is a better marker of lower educational attainment than adolescent alcohol use and identifies an important target population for preventive intervention.

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.

Cannabis use and educational achievement: findings from three Australasian cohort studies.

BACKGROUND: The associations between age of onset of cannabis use and educational achievement were examined using data from three Australasian cohort studies involving over 6000 participants. The research aims were to compare findings across studies and obtain pooled estimates of association using meta-analytic methods. METHODS: Data on age of onset of cannabis use (<15, 15-17, never before age 18) and three educational outcomes (high school completion, university enrolment, degree attainment) were common to all studies. Each study also assessed a broad range of confounding factors. RESULTS: There were significant (p<.001) associations between age of onset of cannabis use and all outcomes such that rates of attainment were highest for those who had not used cannabis by age 18 and lowest for those who first used cannabis before age 15. These findings were evident for each study and for the pooled data, and persisted after control for confounding. There was no consistent trend for cannabis use to have greater effect on the academic achievement of males but there was a significant gender by age of onset interaction for university enrolment. This interaction suggested that cannabis use by males had a greater detrimental effect on university participation than for females. Pooled estimates suggested that early use of cannabis may contribute up to 17% of the rate of failure to obtain the educational milestones of high school completion, university enrolment and degree attainment. CONCLUSIONS: Findings suggest the presence of a robust association between age of onset of cannabis use and subsequent educational achievement.

Assessing evidence for a causal link between cannabis and psychosis: a review of cohort studies.

Over the past five years, the release of cohort studies assessing the link between cannabis and psychosis has increased attention on this relationship. Existing reviews generally conclude that these cohort studies show cannabis has a causal relationship to psychosis, or at least that one cannot be excluded. Few studies have evaluated the relative strengths and limitations of these methodologically heterogeneous cohort studies, and how their relative merits and weaknesses might influence the way the link between cannabis use and psychosis is interpreted. This paper reviews the methodological strengths and limitations of major cohort studies which have looked at the link between cannabis and psychosis, and considers research findings against criteria for causal inference. Cohort studies that assessed the link between cannabis and psychosis were identified through literature searches using relevant search terms and MEDline, PsycINFO and EMBASE. Reference lists of reviews and key studies were hand searched. Only prospective studies of general population cohorts were included. Findings were synthesised narratively. A total of 10 key studies from seven general population cohorts were identified by the search. Limitations were evident in the measurement of psychosis, consideration of the short-term effects of cannabis intoxication, control of potential confounders and the measurement of drug use during the follow-up period. Pre-existing vulnerability to psychosis emerged as an important factor that influences the link between cannabis use and psychosis. Whilst the criteria for causal association between cannabis and psychosis are supported by the studies reviewed, the contentious issue of whether cannabis use can cause serious psychotic disorders that would not otherwise have occurred cannot be answered from the existing data. Further methodologically robust cohort research is proposed and the implications of how evidence informs policy in the case of uncertainty is discussed.

Residential detoxification: essential for marginalised, severely alcohol- and drug-dependent individuals.

INTRODUCTION AND AIMS: In an era of health care rationalisation, residential detoxification services catering for drug- and alcohol-dependent homeless people are being closed. The principal findings of a recent evaluation of a non-medicated residential detoxification service are presented. The aims were to describe the characteristics of residents, their experience of admission, rates of withdrawal completion, referral patterns, staff and key informant perceptions of the service and its role within the wider treatment system. DESIGN AND METHODS: A process evaluation was utilised incorporating interviews with residents (n = 80) and key informants (n = 13); a survey of all service staff (n = 10); and demographic and clinical data for all residents (n = 392) admitted over one calendar year. Results. Residents were heavily substance-dependent and marginalised, with many exhibiting substantial mental and physical health impairments. Polydrug use and frequent prior engagement with drug and alcohol services were common. The majority completed withdrawal and were referred to further treatment. Residents who presented for heroin and other opiate withdrawal were more likely than other residents to leave before completing treatment (odds ratio 2.47, 95% confidence interval 1.48 - 4.15). Information from key informants, service staff and residents converged in underscoring the important role performed by the service. DISCUSSION AND CONCLUSION: Out-patient detoxification for homeless and severely drug- and alcohol-dependent populations is unrealistic. For this group, access to residential detoxification is vital as it provides an environment where potentially serious medical and psychological complications can be managed. There continues to be a clear role for supervised withdrawal in such a setting.