Impact of Major Depressive Disorder on Comorbidities: A Systematic Literature Review.

Objective: To summarize the breadth of data exploring the relationship between major depressive disorder (MDD) and both the incidence and the disease course of a range of comorbidities. Data Sources: The authors searched MEDLINE, Embase, PsycINFO, Cochrane Database of Systematic Reviews, and several prespecified congresses. Searches included terms related to MDD and several comorbidity categories, restricted to those published in the English language from 2005 onward. Study Selection: Eligibility criteria included observational studies within North America and Europe that examined the covariate-adjusted impact of MDD on the risk and/or severity of comorbidities. A total of 6,811 articles were initially identified for screening. Data Extraction : Two investigators extracted data and assessed study quality. Results: In total, 199 articles were included. Depression was significantly ( P  < .05) associated with an increased incidence of dementia and Alzheimer's disease as well as cognitive decline in individuals with existing disease; increased incidence and worsening of cardiovascular disease/events (although mixed results were found for stroke); worsening of metabolic syndrome; increased incidence of diabetes, particularly among men, and worsening of existing diabetes; increased incidence of obesity, particularly among women; increased incidence and worsening of certain autoimmune diseases; increased incidence and severity of HIV/AIDS; and increased incidence of drug abuse and severity of both alcohol and drug abuse. Conclusions: The presence of MDD was identified as a risk factor for both the development and the worsening of a range of comorbidities. These results highlight the importance of addressing depression early in its course and the need for integrating mental and general health care.