Objective: While recent studies have suggested an association between obesity and common mental disorders, findings across different studies have varied and the nature of any relationship remains uncertain. The aim of this study was to examine the relationship between depression, anxiety, and two different measures of obesity in a large community-based sample.
Methods: The HUNT-2 study was used to conduct a cross-sectional study of 65,648 adults between 20 and 89 years of age. During a clinical examination, trained nurses took various anthropometric measurements allowing participants' body mass index (BMI) and waist-hip ratio (WHR) to be calculated. Anxiety and depressive symptoms were ascertained using the Hospital Anxiety and Depression Scale. Information regarding physical activity, level of social support, and medical comorbidity was also obtained.
Results: Elevated WHR was associated with increased prevalence of both anxiety and depression. After adjustment for BMI, physical activity, social isolation, and somatic diseases, WHR remained independently associated with depression in both males and females and with anxiety among males. Obesity, as defined by BMI, was associated with depression; however, this association was strongly attenuated by WHR. There was a negative association between BMI and anxiety in both genders.
Conclusion: Abdominal fat distribution (as measured by WHR) appears to be the key mediator in the relationship between obesity and depression. Increased BMI was not independently associated with depression and may provide some protection against anxiety. These findings are consistent with a hypothesis that links obesity and depression via metabolic disturbances involving the hypothalamic-pituitary-adrenocortical axis.