Relationships between body mass index, mental health, and suicidal ideation: population perspective using two methods

Objective: The aim of the present study was to examine the relationship between body mass index (BMI), mental health, and suicidal ideation in a general population. Method: Two random and representative samples were drawn from the South Australian population. The interview techniques differed, as did the measures of depression and suicidality. One involved 3034 people in face-to-face interviews, and the other involved 30 214 persons providing information via a computer-assisted telephone interviewing (CATI) system. BMI was classified according to World Health Organization criteria. In face-to-face interviews, major depression was defined by the Primary Care Evaluation of Mental Disorders (PRIME-MD) and suicidal ideation by direct enquiry. In the CATI data, psychological distress was assessed on the Kessler 10 instrument and suicidal ideation by four items on the General Health Questionnaire (GHQ). Data analysis controlled for demographic and physical health variables. Results: In the face-to-face interviews, the combined obese and morbidly obese men were significantly less likely to have major depression or suicidal ideation than those of a healthy weight. For the telephone interview-derived data, the only significant finding was for overweight women to report less psychological distress than those of a healthy weight. Conclusions: It is no longer tenable to assume that increased BMI is necessarily associated with major depression, psychological distress, or suicidal ideation. Indeed, it appears protective for some people.