Exploring a causal model in observational cohort data: The role of parents and peers in shaping substance use trajectories

C J Greenwood; G J Youssef; P Letcher; E A Spry; K C Thomson; L J Hagg; D M Hutchinson; J A Macdonald; J McIntosh; A Sanson; J W Toumbourou; C A Olsson

doi:10.1016/j.addbeh.2020.106597

Exploring a causal model in observational cohort data: The role of parents and peers in shaping substance use trajectories

Addict Behav. 2021 Jan:112:106597. doi: 10.1016/j.addbeh.2020.106597. Epub 2020 Aug 5.

Authors

C J Greenwood¹, G J Youssef², P Letcher³, E A Spry², K C Thomson⁴, L J Hagg⁵, D M Hutchinson⁶, J A Macdonald⁷, J McIntosh⁸, A Sanson³, J W Toumbourou⁵, C A Olsson⁷

Affiliations

¹ Deakin University, Centre for Social and Early Emotional Development, School of Psychology, Faculty of Health, Geelong, Australia; Murdoch Children's Research Institute, Centre for Adolescent Health, Melbourne, Australia. Electronic address: christopher.greenwood@deakin.edu.au.
² Deakin University, Centre for Social and Early Emotional Development, School of Psychology, Faculty of Health, Geelong, Australia; Murdoch Children's Research Institute, Centre for Adolescent Health, Melbourne, Australia.
³ University of Melbourne, Department of Paediatrics, Royal Children's Hospital, Australia.
⁴ Deakin University, Centre for Social and Early Emotional Development, School of Psychology, Faculty of Health, Geelong, Australia; University of Melbourne, Department of Paediatrics, Royal Children's Hospital, Australia.
⁵ Deakin University, Centre for Social and Early Emotional Development, School of Psychology, Faculty of Health, Geelong, Australia.
⁶ Deakin University, Centre for Social and Early Emotional Development, School of Psychology, Faculty of Health, Geelong, Australia; Murdoch Children's Research Institute, Centre for Adolescent Health, Melbourne, Australia; University of Melbourne, Department of Paediatrics, Royal Children's Hospital, Australia; University of New South Wales, National Drug and Alcohol Research Centre, Faculty of Medicine, Australia.
⁷ Deakin University, Centre for Social and Early Emotional Development, School of Psychology, Faculty of Health, Geelong, Australia; Murdoch Children's Research Institute, Centre for Adolescent Health, Melbourne, Australia; University of Melbourne, Department of Paediatrics, Royal Children's Hospital, Australia.
⁸ Deakin University, Centre for Social and Early Emotional Development, School of Psychology, Faculty of Health, Geelong, Australia; Murdoch Children's Research Institute, Centre for Adolescent Health, Melbourne, Australia; La Trobe University, School of Psychology and Public Health, Victoria, Australia.

PMID: 32823031
DOI: 10.1016/j.addbeh.2020.106597

Abstract

Aims: To explore the process of applying counterfactual thinking in examining causal determinants of substance use trajectories in observational cohort data. Specifically, we examine the extent to which quality of the parent-adolescent relationship and affiliations with deviant peers are causally related to trajectories of alcohol, tobacco, and cannabis use across adolescence and into young adulthood.

Methods: Data were drawn from the Australian Temperament Project, a population-based cohort study that has followed a sample of young Australians from infancy to adulthood since 1983. Parent-adolescent relationship quality and deviant peer affiliations were assessed at age 13-14 years. Latent curve models were fitted for past month alcohol, tobacco, and cannabis use (n = 1590) from age 15-16 to 27-28 years (5 waves). Confounding factors were selected in line with the counterfactual framework.

Results: Following confounder adjustment, higher quality parent-adolescent relationships were associated with lower baseline cannabis use, but not alcohol or tobacco use trajectories. In contrast, affiliations with deviant peers were associated with higher baseline binge drinking, tobacco, and cannabis use, and an earlier peak in the cannabis use trajectory.

Conclusions: Despite careful application of the counterfactual framework, interpretation of associations as causal is not without limitations. Nevertheless, findings suggested causal effects of both parent-adolescent relationships and deviant peer affiliations on the trajectory of substance use. Causal effects were more pervasive (i.e., more substance types) and protracted for deviant peer affiliations. The exploration of causal relationships in observational cohort data is encouraged, when relevant limitations are transparently acknowledged.

Keywords: Adolescence; Causal modeling, substance use; Parents; Peers; Trajectory; Young adulthood.

Publication types

Observational Study
Research Support, Non-U.S. Gov't

MeSH terms

Adolescent
Adult
Australia / epidemiology
Cohort Studies
Humans
Longitudinal Studies
Parents
Peer Group*
Risk Factors
Substance-Related Disorders* / epidemiology
Young Adult