title: Developmental trajectories of adolescent cannabis use and their relationship to young adult social and behavioural adjustment: A longitudinal study of Australian youth.
abstract: This study aimed to identify distinct developmental trajectories (sub-groups of individuals who showed similar longitudinal patterns) of cannabis use among Australian adolescents, and to examine associations between trajectory group membership and measures of social and behavioural adjustment in young adulthood. Participants (n=852, 53% female) were part of the International Youth Development Study. Latent class growth analysis was used to identify distinct trajectories of cannabis use frequency from average ages 12 to 19, across 6 waves of data. Logistic regression analyses and analyses of covariance were used to examine relationships between trajectory group membership and young adult (average age: 21) adjustment, controlling for a range of covariates. Three trajectories were identified: abstainers (62%), early onset users (11%), and late onset occasional users (27%). The early onset users showed a higher frequency of antisocial behaviour, violence, cannabis use, cannabis-related harms, cigarette use, and alcohol harms, compared to the abstinent group in young adulthood. The late onset occasional users reported a higher frequency of cannabis use, cannabis-related harms, illicit drug use, and alcohol harms, compared to the abstinent group in young adulthood. There were no differences between the trajectory groups on measures of employment, school completion, post-secondary education, income, depression/anxiety, or alcohol use problems. In conclusion, early onset of cannabis use, even at relatively low frequency during adolescence, is associated with poorer adjustment in young adulthood. Prevention and intervention efforts to delay or prevent uptake of cannabis use should be particularly focussed on early adolescence prior to age 12.
authors.affiliation: Learning Sciences Institute Australia, Faculty of Education and Arts, Australian Catholic University, 115 Victoria Pde, Fitzroy, Victoria, Australia; School of Psychology, Faculty of Health Sciences, Australian Catholic University, 115 Victoria Pde, Fitzroy, Victoria, Australia. Electronic address: kirsty.balog@acu.edu.au.
authors.forename: Kirsty E
authors.initials: KE
authors.lastname: Scholes-Balog
authors.affiliation: Learning Sciences Institute Australia, Faculty of Education and Arts, Australian Catholic University, 115 Victoria Pde, Fitzroy, Victoria, Australia; School of Psychology, Faculty of Health Sciences, Australian Catholic University, 115 Victoria Pde, Fitzroy, Victoria, Australia; Department of Paediatrics, The University of Melbourne, Parkville, Victoria, Australia; Centre for Adolescent Health, Murdoch Childrens Research Institute, Parkville, Victoria, Australia; School of Psychology, Deakin University, Burwood, Victoria, Australia. Electronic address: sheryl.hemphill@acu.edu.au.
authors.forename: Sheryl A
authors.initials: SA
authors.lastname: Hemphill
authors.affiliation: Department of Paediatrics, The University of Melbourne, Parkville, Victoria, Australia; Centre for Adolescent Health, Murdoch Childrens Research Institute, Parkville, Victoria, Australia. Electronic address: tracy.evanswhipp@mcri.edu.au.
authors.forename: Tracy J
authors.initials: TJ
authors.lastname: Evans-Whipp
authors.affiliation: Centre for Adolescent Health, Murdoch Childrens Research Institute, Parkville, Victoria, Australia; School of Psychology, Deakin University, Burwood, Victoria, Australia; Prevention Sciences, Centre for Social and Early Emotional Development, Deakin University, Geelong, Victoria, Australia. Electronic address: john.toumbourou@deakin.edu.au.
authors.forename: John W
authors.initials: JW
authors.lastname: Toumbourou
authors.affiliation: Department of Paediatrics, The University of Melbourne, Parkville, Victoria, Australia; Centre for Adolescent Health, Murdoch Childrens Research Institute, Parkville, Victoria, Australia. Electronic address: george.patton@rch.org.au.
authors.forename: George C
authors.initials: GC
authors.lastname: Patton
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology*; D000328:Adult; D000367:Age Factors; D002648:Child; D015331:Cohort Studies; D004522:Educational Status; D004651:Employment / Q000523:psychology / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008385:Marijuana Smoking / Q000523:psychology*; D000066553:Problem Behavior / Q000523:psychology*; D012917:Social Adjustment; D014739:Victoria; D055815:Young Adult
keywords: Adjustment; Adolescence; Cannabis use; Longitudinal study; Trajectories; Young adulthood