Association between Body Mass Index and Mental Health among Scottish Adult Population: a Cross-Sectional Study of 37,272 Participants
The evidence is conflicting as to whether body mass index (BMI) is associated with mental health and, if so, to what extent it varies by sex and age. We studied mental health across the full spectrum of BMI among the general population, and conducted subgroup analyses by sex and age.
METHODS:
We undertook a cross-sectional study of a representative sample of the Scottish adult (≥16 years) population. The Scottish Health Survey provided data on mental health, measured by the General Health Questionnaire (GHQ), BMI, demographic and lifestyle information. Good mental health was defined as a GHQ score <4, and poor mental health as a GHQ score ≥4. Logistic regression models were applied.
RESULTS:
Of the 37,272 participants, 5,739 (15.4%) had poor mental health. Overall, overweight participants had better mental health than the normal-weight group (adjusted OR 0.93, 95% CI 0.87, 0.99, p=0.049), and individuals who were underweight, class II or class III obese had poorer mental health (class III obese group: adjusted OR 1.26, 95% CI 1.05, 1.51, p=0.013). There was a significant interaction with sex (p=0.013), and age (p=<0.001). Being overweight was associated with significantly better mental health in middle-aged men only. In contrast being underweight in all ages and obese at young age was associated with significantly poorer mental health in women only.
CONCLUSIONS:
The adverse associations between adiposity and mental health are specific to women. Underweight women and young women who are obese have poorer mental health. In contrast, middle-aged overweight men have better mental health.