Seventy-five years of comorbidity research.

Objective: As part of the 75th anniversary edition of the Journal of Studies on Alcohol and Drugs, this article reviews research on the relationship between mental disorders and substance use disorders ("comorbidity") from 1940--the journal's inception--to the present.

Method: First, a survey of the titles and abstracts of all articles published in the journal was used to identify those articles pertaining to comorbidity. Seminal and representative works from this set of articles and a limited selection of articles from other journals were included in the review.

Results: The early psychosocial research emphasized psychoanalytic formulations of alcohol use as a defensive symptom, which informed the early experimental research on the tension-reducing properties of alcohol. The "cognitive revolution," occurring in the 1970s, enabled an expansion of the tension-reduction theory to include a central role for mental processes (e.g., alcohol expectancies) in promoting drinking to cope with negative affectivity. The early clinical research characterized mental conditions commonly co-occurring with alcohol disorders and considered their etiological relationship to alcohol disorders. The "neo-Kraepelinian revolution" in psychiatry, which also occurred in the 1970s, infused the clinical comorbidity research with a more rigorous diagnostic technology and a range of biomedical research methodologies to study the mechanistic linkages of co-occurring disorders.

Conclusions: Although a substantial quantity of scientific information on comorbidity has accumulated over the past 75 years, a standard model(s) of comorbidity has yet to congeal. Barriers and opportunities related to achieving this important goal are discussed.