Measurement matters in the association between early adolescent depressive symptoms and body mass index.

OBJECTIVE: The objectives of this study were to examine associations between depressive symptoms and body mass over 1 year during early adolescence and to assess how the associations might differ depending upon whether self-reported or directly measured height and weight were used. METHOD: Participants were 446 sixth-grade Seattle students. Depressive symptoms were assessed using the Mood and Feelings Questionnaire. Regression models were used to examine whether baseline depression status was associated with 12-month body mass index (BMI; using self-reported height and weight) and whether baseline overweight status was associated with 12-month depressive symptom score. Analyses were rerun among a subsample (n=165) who had height and weight directly measured. RESULTS: Using BMI derived from self-reported values, depressed males had a significantly lower BMI than nondepressed males, while depressed females had a significantly higher BMI than nondepressed females, after adjusting for covariates. Among a subsample using measured height and weight values, however, depression was no longer associated with BMI in either gender. Baseline overweight status did not predict 12-month depression score. CONCLUSIONS: Observed associations between depression and subsequent BMI were explained by differential misclassification of self-reported height and weight by depression status and gender. Direct measurement of height and weight may be necessary to ensure validity in studies of adolescent depression and weight-related outcomes.