Do You Drink Because You’re Depressed, or Are You Depressed Because You Drink?

Debate continues about whether the comorbidity of depressive and substance use disorders results from a common diathesis, or whether one disorder causes or lowers the threshold for the other. This 25-year longitudinal study of 1265 New Zealanders followed from childhood to age 25 helps to clarify the question.

At ages 18, 21, and 25, subjects underwent structured interviews for DSM-IV disorders. At these points, 14% to 22% of participants met criteria for alcohol abuse or dependence (AAD), and 14% to 18% met criteria for major depressive disorder (MDD). At the three observation periods, individuals with one disorder were significantly more likely to have the other disorder. Controlling for multiple possible intervening variables including ot…