The relationship between body mass index and mental health

Background The association between atypical body weight and mental health remains poorly understood. We examined the relationship between body mass index and mental health in a population-based study of adults that included the full range of body weights, three disorder types, and three levels of mental illness severity. Methods Data came from the 2003 Alberta Mental Health Survey (n = 5383), which included a validated, standard instrument for measurement of DSM-IV mental disorders as well as several indicators of psychiatric symptoms. Associations were examined using crosstabulation and chi squared statistics, and logistic regression adjusting for sociodemographic variables. Results Findings differed by type and severity of mental illness and by sex and age. For instance, anxiety disorders were elevated among underweight men compared to normal weight men and to women. Substance use disorders were elevated among obese men at younger compared to older ages. Mood disorders were elevated among obese women compared to normal weight women, and subclinical anxiety/ depression was reduced among obese men compared to normal weight men and to women. Conclusions These analyses highlight the importance of considering type of mental illness, level of severity, sex and age when examining the relationship between BMI and mental health. The diversity of patterns observed, detectable at the population level, warrant further examination and monitoring.