Association between anxiety disorders and substance use disorders among young persons: results of a 21-year longitudinal study.

Objective: To examine the linkages between anxiety disorders and the development of substance use disorders in a birth cohort of young people studied to young adulthood.

Methods: Data were gathered over the course of a longitudinal study of a birth cohort of over 1000 New Zealand born young people. Over the course of the study, data were gathered on: (a) anxiety disorders and substance use disorders at ages 16-18 and 18-21; (b) a range of potential confounding factors including measures of childhood, social, and family factors.

Results: Young people with anxiety disorders had odds of substance dependence that were between 1.3 and 3.9 times higher than young people without anxiety disorders. These associations were largely explained by a series of covariate factors relating to: (a) childhood and family factors; (b) prior substance dependence; (c) comorbid depression; (d) peer affiliations. After adjustment for these factors, anxiety disorder was unrelated to all measures of substance use.

Conclusions: Young people with anxiety disorders are at increased risk of substance dependence. However, this association appears to be largely or wholly non causal and reflects the associations between childhood factors, prior substance dependence, comorbid depression, peer affiliations and the development of anxiety disorders.