Obesity and Depression in Adolescence and Beyond: Reciprocal Risks

Introduction: Obesity and Major Depressive Disorder (MDD) are associated, but evidence about how they relate over time is conflicting. The goal of this study was to examine prospective associations between MDD and obesity from early adolescence through early adulthood.  Methods: Participants were drawn from a statewide, community-based, Minnesota sample (the Minnesota Twin Family Study; n=752 males, 760 females). MDD and obesity with onsets by early adolescence (by age 14), late adolescence (between 14 and 20), and early adulthood (ages 20 to 24) were assessed via structured interview (for MDD) and study-measured height and weight (for obesity; i.e., body mass index greater than 30). Retention rates were strong (averaging over 90% at each wave). Longitudinal analyses were conducted using generalized estimating equations to account for the nested nature of the data (twins within families).  All analyses included a term representing the interaction of the independent variable and the sex of the participant in order to assess potential gender differences in these associations.  Results: Cross-sectional results indicated that MDD and obesity with onsets by early adolescence were concurrently associated, but the same was not true later in development.  Longitudinal results indicated that MDD by early adolescence predicted the onset of obesity (odds ratio=3.76, confidence interval= 1.33-10.59) during late adolescence among females (but not males; the interaction effect by sex was significant).  Obesity that developed during late adolescence predicted the onset of MDD (odds ratio=5.89, confidence interval= 2.31-15.01) during early adulthood among females (but not males; the interaction effect by sex was significant).  Conclusions: For girls, adolescence is a high risk period for the development of this comorbidity, with the nature of the risk varying over the course of adolescence. Early adolescent-onset depression is associated with elevated risk of later onset obesity, and obesity, particularly in late adolescence, is associated with increased odds of later depression.  Further investigation into the mechanisms of these effects and the reasons for the observed gender and developmental differences is needed.  Prevention programs focused on early-onset cases of depression and adolescent-onset cases of obesity, particularly among females, may help in reducing risk for this form of comorbidity.