Objective: To investigate the relationship of symptoms of depression to weight changes in healthy individuals of normal weight across a follow-up of over 20 y.
Participants and design: College students (3885 men and 841 women) were administered a self-report depression measure in the mid-1960s. Their baseline body mass index (BMI) was calculated from their college medical records. Participants were contacted by mail in the late 1980s and asked to report their current height and weight as well as their smoking and exercise habits. Another measure of depressive symptoms was obtained from 3560 individuals at follow-up. Multiple regression models were used to relate changes in weight to depression scores while controlling for background (gender, baseline BMI and the gender by BMI interaction) and behavioral (exercise and smoking) predictors.
Results: The relationship between depressive symptoms and body weight change took the form of an interaction with baseline BMI (P < 0.001). Those with high baseline depression scores gained less weight than their nondepressed counterparts if they were initially lean, but more if they were initially heavy. This trend was especially strong in those with high depression scores at both baseline and follow-up.
Conclusions: The findings support the hypothesis that depression exaggerates pre-existing weight change tendencies. This pattern would not have been detected by an examination of main effects alone, illustrating the need to move toward more complicated interactive models in the study of psychological factors and weight.