AbstractThe diagnosis of depression has been viewed as an important factor in the treatment response for those who have alcohol and other drug dependence. The objective of the study was to examine the prevalence of a lifetime history of major depression in inpatients with a substance use disorder in addictions treatment. An evaluation study of 6,355 patients was conducted in inpatient and outpatient addictions treatment programs from 41 sites. Subjects were required to have a substance use disorder and to be evaluated for a lifetime diagnosis of major depression according to DSM-III-R criteria. The rate of a lifetime diagnosis of major depression was 43.7%. The most common diagnosis was alcohol dependence, followed by cocaine dependence, and cannabis dependence). Depression was associated in significantly greater numbers with diagnoses involving drugs other than alcohol, in females greater than in males, with number and frequency of use, and in inpatient programs more than outpatient programs. The rates for continuous abstinence at one year did not differ between those with and without a lifetime history of depression.