Obesity and depression in US women: results from the 2005-2006 National Health and Nutritional Examination Survey.

Research is needed to better elucidate the relationship between obesity and depression, which has been most consistently demonstrated for women, but not for men. We examined exclusively a population-based sample of US women who participated in the 2005 or 2006 National Health and Nutritional Examination Survey. Current depression was defined as having a score of > or =10 (a conventional threshold for moderate symptoms of depression) or meeting the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) diagnostic criteria for major depression on the nine-item Patient Health Questionnaire. Weight and height were measured and BMI was calculated. Waist circumference, a clinical measure of abdominal obesity, was also measured. BMI was positively associated with the probability of moderate/severe depressive symptoms (r = 0.49, P = 0.03) and major depression (r = 0.72, P < 0.0001). The probability curves increased progressively, beginning at BMI of 30. Degree of obesity was an independent risk factor for depression even within the obese population, and women in obesity class 3 (BMI > or =40) were at particular risk (odds ratio (OR) = 4.91, 95% confidence interval (CI): 1.17-20.57), compared to those in obesity class 1 (BMI 30 to <35). Abdominal obesity was positively associated with depressive symptoms, but not major depression, independent of general obesity (BMI). In addition to severe obesity, compromised physical health status, young or middle-aged adulthood, low income, and relatively high education were also independently associated with greater odds of depressive symptoms among obese women. These characteristics may identify specific at-risk subgroups of obese women in which hypothesized causal pathways and effective preventive and therapeutic interventions can be profitably investigated.