Abstract
Background: This study examined the associations between the transition to parenthood and substance use disorders from ages 18 to 30 in a New Zealand birth cohort. Methods: Outcomes included: DSM-IV criteria for: (a) alcohol abuse/dependence (AAD) and (b) illicit substance abuse/dependence. The study also used measures transition to parenthood during the period 18-30 years; and observed covariate factors including: family socio-economic status; family functioning; childhood abuse exposure; childhood personal and behavioural characteristics; and psychosocial adjustment in adolescence. Data were analysed using repeated measures Generalised Estimating Equation models, and conditional fixed effects regression modelling to control for confounding. Gender interactions were examined using moderated regression analyses. Results: Those who became parents had unadjusted odds of substance use disorder outcomes that were approximately 50% lower than those who had not become parents. Adjustment of the associations for both: (a) observed confounding factors and (b) non-observed fixed effects; strengthened the associations between parenthood status and substance use disorders. Custodial parents had odds of substance use disorders that were 57-78% lower than those who did not become parents after adjusting for non-observed fixed effects. Additional analyses suggested these effects were confined to custodial parents only. There was also evidence for gender × parenthood status interactions for AAD, with the effects of parenthood on AAD being stronger for females. Conclusions: The results suggest that the transition to custodial parenthood may result in reduced risks of substance use disorder, particularly amongst female cohort members.