This study was the first of its kind to use integrative data analyses – a highly innovative approach – to pool data from four large and long-running Australasian cohort studies to better understand the link between cannabis use and later-life outcomes. Dramatically improved knowledge of these relationships has created a clearer picture of the interventions required to reduce the harms associated with cannabis use.

Project Collaborators External

• Professor Steve Allsop National Drug Research Institute, Curtin University
• Carolyn CoffeyMurdoch Childrens Research Institute, University of Melbourne
• Dr David Ferguson Christchurch Health and Development Study, University of Otago
• Professor Wayne Hall School of Population Health, University of Queensland
• Dr Mohammad Hayatbakhsh School of Population Health, University of Queensland
• A/Prof John Horwood Christchurch Health and Development Study, University of Otago
• Doctor Primrose Letcher Royal Children’s Hospital, Deakin University
• Professor Jake Najman School of Population Health, University of Queensland
• Dr Craig Olsson Murdoch Childrens Research Institute , University of Melbourne
• Professor George Patton Murdoch Childrens Research Institute , University of Melbourne
• Doctor Rachel Skinner Children’s Hospital Westmead, University of Sydney
• Elizabeth Spry Murdoch Childrens Research Institute , University of Melbourne
• Dr Robert Tait Centre for Mental Health Research, Australian National University
• Professor John Toumbourou School of Psychology, Deakin University

Project Supporters

National Health & Medical Research Council - Project Grant|APP1009381

This study had the broad aim of producing more comparable and robust findings about the linkages between cannabis use, mental health, other substance use and social development in young people. Specifically, the study aimed to:

• develop integrative analyses across four large and long-running Australasian cohorts of the linkages between the use of cannabis and secondary school completion, university degree attainment, depression, self harm, other illicit drug use, welfare and dependence
• obtain pooled estimates of the effect of cannabis use on other drug use, mental health and social development in young people to provide better estimates of the relationships between cannabis use and particular life-course outcomes
• more fully utilise existing cohort data.

Design and Method

The study used an integrative data analyses framework. Data was harmonised from four long-running Australasian cohort studies which span early childhood, adolescence and young adulthood: The Australian Temperament Project (ATP), The Christchurch Health and Development Study (CHDS), The Mater Hospital and University of Queensland Study of Pregnancy (MUSP), and Victorian Adolescent Health Cohort Study(VAHCS). Combined, the studies involve over 12,000 young people.

Progress/Update

In 2013:

A consistent metric for the exposure variables and outcomes of interest were established across the cohort studies involved and data harmonised into a single dataset. Two papers completed and prepared for publication (see below). An additional paper commenced which investigated the genetic prediction of early onset cannabis use and young adult outcomes. Two additional papers outlined for possible future work: (1) Child behaviour problems in the prediction of age of cannabis onset; and, (2) Examining the course of cannabis dependence in young adulthood.

Benefits

This study produced comparable analyses and better estimates of the relationships between early cannabis use and adverse life-course outcomes. The study extends previous research on the link between adolescent cannabis use and problems later in life by integrating data from multiple sources and providing control for a broader range of covariates than possible in traditional meta-analyses. The findings provide stronger evidence of the potential harms of adolescent cannabis use across a number of domains. The prevention or delay of cannabis use in adolescence may have broad health and social benefits. The findings suggest that efforts to reform cannabis legislation should be carefully evaluated to ensure they reduce adolescent cannabis use and prevent potentially adverse developmental effects.

In 2013:

Hutchinson, M., Silins, E., Mattick. R., Patton, G., Fergusson, D., Hayatbakhsh, M., Toumbourou, J., Olsson, C., Spry, E., Tait, R., Degenhardt, L., Swift, W., Butterworth, P., Horwood, LJ., andthe Cannabis Cohorts Research Consortium (CCRC). Cohort profile: The Cannabis Cohorts Research Consortium (CCRC) Combined and Harmonised Cohort.

Silins, E., Horwood, LJ., Patton, G., Fergusson, D., Olsson, C., Hutchinson, D., Spry, E., Toumbourou, J., Degenhardt, L., Swift, W., Coffey, C., Tait, R., Letcher, P., Copeland, J., Mattick, R., andthe Cannabis Cohorts Research Consortium (CCRC). Young adult sequelae of adolescent cannabis use: An integrative analysis across three Australasian Cohorts.

Study findings presented at the Australian Professional Society on Alcohol and other Drugs Conference (Brisbane, QLD), and at the NIDA International Forum and the College of Problems of Drug Dependence Annual Meeting (San Diego, CA): Silins, E., Olsson, C., Horwood, J., Hutchinson, D., Spry, E., Patton, G., Fergusson, D., Toumbourou, J.W., Mattick, R., & the Cannabis Cohort Research Consortium. Early onset cannabis use and young adult outcomes: An integrative data analysis of three Australasian cohorts.

Further NHMRC funding received to extend the study to investigate adolescent binge-drinking using data from multiple sources.

In 2012:

Published paper: Horwood, LJ., Fergusson, D., Coffey, C., Patton, G., Tait, R., Smart, D., Letcher, P., Silins, E., Hutchinson, D. (2012). Cannabis and depression: An integrative data analysis of four Australasian cohorts. Drug and Alcohol Dependence, 126 (3): 369-378.

Two papers were presented at the National Cannabis Conference, 20^th September 2012, Brisbane:

(1) Silins, E., Patton, G., Horwood, L. J., Fergusson, D., Letcher, P., Coffey, C., Toumbourou, J., Hutchinson, D., Degenhardt, L., Swift, W., Hayatbakhsh, M., Mattick, R., Olsson, C., Allsop, S., Copeland, J., Hall, W., Najman, J., Rodgers, B., Skinner, R., Slade, T., Tait, R. Early onset cannabis use and young adult outcomes: A prognostic study across three Australasian cohorts; and,

(2) Olsson, C., Horwood, L. J., Silins, E., Hutchinson, D., Patton, G., Toumbourou, J., Fergusson, D., Mattick, R., Degenhardt, L., Hayatbakhsh, M., Swift, W., Allsop, S., Coffey, C., Copeland, J., Hall, W., Najman, J., O’Connor, M., Rodgers, B., Skinner, R., Slade, T., Tait, R. Genetic prediction of early onset cannabis use and young adult outcomes: A consortium based approach to well powered studies of genetic risk.