"Both depression and obesity are widely spread problems with major public health implications," the authors write as background information in the article. "Because of the high prevalence of both depression and obesity, and the fact that they both carry an increased risk for cardiovascular disease, a potential association between depression and obesity has been presumed and repeatedly been examined." Understanding the relationship between the two conditions over time could help improve prevention and intervention strategies.
Floriana S. Luppino, M.D., of Leiden University Medical Center and GGZ Rivierduinen, Leiden, the Netherlands, and colleagues analyzed the results of 15 previously published studies involving 58,745 participants that examined the longitudinal (over time) relationship between depression and overweight or obesity.
"We found bidirectional associations between depression and obesity: obese persons had a 55 percent increased risk of developing depression over time, whereas depressed persons had a 58 percent increased risk of becoming obese," the authors write. "The association between depression and obesity was stronger than the association between depression and overweight, which reflects a dose-response gradient."
Sub-analyses demonstrated that the association between obesity and later depression was more pronounced among Americans than among Europeans, and stronger for diagnosed depressive disorder compared with depressive symptoms.
Evidence of a biological link between overweight, obesity and depression remains uncertain and complex, but several theories have been proposed, the authors note. Obesity may be considered an inflammatory state, and inflammation is associated with the risk of depression. Because thinness is considered a beauty ideal in both the United States and Europe, being overweight or obese may contribute to body dissatisfaction and low self-esteem that places individuals at risk for depression. Conversely, depression may increase weight over time through interference with the endocrine system or the adverse effects of antidepressant medication.
The findings are important for clinical practice, the authors note. "Because weight gain appears to be a late consequence of depression, care providers should be aware that within depressive patients weight should be monitored. In overweight or obese patients, mood should be monitored. This awareness could lead to prevention, early detection and co-treatment for the ones at risk, which could ultimately reduce the burden of both conditions," they conclude.
Archives of General Psychiatry