they interact a huge amount, but can be quite complexly intertwined. and... would depend on the particular individual. a bipolar individual will have poor impulse control... leading to drug use. a depressed person may have triggers, context in which alcohol figures prominently. In the Other Direction. Alcohol just kills off some brain functions. (takes a while and heavy use) and... then the brain is permanently altered and predisposed to depression (and espcially pre-disposed to sleep problems). so.... you d need a coordinated approach by a primary care physician who sees a lot of people with substance abuse. (inner city clinic).