Anxiety disorders and drug dependence: evidence on sequence and specificity among adults

The goal of this study was to investigate the relation between specific anxiety disorders and substance dependence, adjusting for potentially confounding demographic factors (e.g. sex) and comorbidity (e.g. alcohol dependence, major depression), among adults in the USA.

Data were drawn from the National Comorbidity Survey (NCS), a nationally representative population sample of the US adult population aged 15-54. The temporal sequence of onset of anxiety and substance dependence disorders was examined.

Substance dependence temporally precedes several anxiety disorders, particularly panic disorder. Specifically, a history of past substance dependence predicts current panic disorder (odds ratio [OR] =2.62, 95% confidence interval [CI] =1.29, 5.32), social phobia (OR=1.7, 95%CI=1.12, 2.41), and agoraphobia (OR=1.78, 95%CI=1.08, 2.94). Conversely, in more than 50% of substance abuse disorder cases, in nearly 40% of post-traumatic stress disorder (PTSD) cases, and in nearly 30% of generalized anxiety disorder (GAD) cases, the anxiety disorder has first onset. Similarly, a lifetime history of social phobia, PTSD, or GAD significantly predicts lifetime substance dependence (OR=1.51 for social phobia, 2.06 for PTSD, 1.45 for GAD).

For any particular anxiety disorder, a diagnosis of substance abuse can occur prior to or subsequent to an anxiety disorder. Nevertheless, there is also evidence for the specificity of some associations between anxiety and substance dependence disorders; these are independent of the effects of sex and other comorbid disorders, may be causal in nature, and deserve particular attention in clinical settings. The possibility that within a particular anxiety disorder there are a variety of mechanisms of association with various substances should be addressed in future work.