Aims: To examine the literature on the associations between alcohol use disorders (AUD) and major depression (MD), and to evaluate the evidence for the existence of a causal relationship between the disorders.

Methods: PsycInfo; PubMed; Embase; Scopus; ISI Web of Science database searches for studies pertaining to AUD and MD from the 1980 to the present. Random-effects models were used to derive estimates of the pooled adjusted odds ratios (AOR) for the links between AUD and MD among studies reporting an AOR.

Results: The analysis revealed that the presence of either disorder doubled the risks of the second disorder, with pooled AORs ranging from 2.00 to 2.09. Epidemiological data suggest that the linkages between the disorders cannot be accounted for fully by common factors that influence both AUD and MD, and that the disorders appear to be linked in a causal manner. Further evidence suggests that the most plausible causal association between AUD and MD is one in which AUD increases the risk of MD, rather than vice versa. Potential mechanisms underlying these causal linkages include neurophysiological and metabolic changes resulting from exposure to alcohol. The need for further research examining mechanisms of linkage, gender differences in associations between AUD and MD and classification issues was identified.

Conclusions: The current state of the literature suggests a causal linkage between alcohol use disorders and major depression, such that increasing involvement with alcohol increases risk of depression. Further research is needed in order to clarify the nature of this causal link, in order to develop effective intervention and treatment approaches.