Depression and anxiety among US adults: associations with body mass index

Background: Obesity is associated with an increased risk of developing a variety of chronic diseases, most of which are associated with psychiatric disorders. We examined the associations of depression and anxiety with body mass index (BMI) after taking into consideration the obesity-related comorbidities (ORCs) and other psychosocial or lifestyle factors. Methods: We analyzed the data collected from 177 047 participants (aged >= 18 years) in the 2006 Behavioral Risk Factor Surveillance System. Current depression was assessed by the Patient Health Questionnaire-8 diagnostic algorithm. Lifetime diagnoses of depression, anxiety and ORCs were self-reported. The prevalence of the three psychiatric disorders was age standardized to the 2000 US population. Multivariate-adjusted prevalence ratios were computed to test associations of depression and anxiety with BMI using SUDAAN software. Results: The age-adjusted prevalence of current depression, lifetime diagnosed depression and anxiety varied significantly by gender. Within each gender, the prevalence of the three psychiatric disorders was significantly higher in both men and women who were underweight (BMI<18.5 kg/m(2)), in women who were overweight (BMI: 25-<30 kg/m(2)) or obese (BMI >= 30 kg/m(2)), and in men who had class III obesity (BMI >= 40 kg/m(2)) than in those with a normal BMI (18.5 - <25 kg/m(2)). After adjusting for demographics, ORCs, lifestyle or psychosocial factors, compared with men with a normal BMI, men with a BMI >= 40 kg/m(2) were significantly more likely to have current depression or lifetime diagnosed depression and anxiety; men with a BMI<18.5 kg/m(2) were also significantly more likely to have lifetime diagnosed depression. Women who were either overweight or obese were significantly more likely than women with a normal BMI to have all the three psychiatric disorders. Conclusions: Our results demonstrate that disparities in the prevalence of depression and anxiety exist among people with different BMI levels independent of their disease status or other psychosocial or lifestyle factors.