Depression trajectories, inflammation, and lifestyle factors in adolescence: The TRacking Adolescents' Individual Lives Survey

Objective: In adults, depression and inflammation are bidirectionally related. This association is less clear in adolescents. Moreover, somatic and cognitive depressive symptoms might be differentially related to inflammation. Lifestyle factors, as in adults, may play an important mediating role in adolescents. For the current study we evaluated trajectories of depressive symptoms in adolescence over a 5-year course and their relation with subsequent high-sensitivity C-reactive protein (hsCRP) levels, and examined lifestyle factors as mediators. Method: Participants of the TRacking Adolescents’ Individual Lives’ Survey (TRAILS; N = 1166) were followed from 2001 until 2008. Three biennial youth self-report (YSR) assessments of depressive symptoms were taken. Demographics, health, and lifestyle factors and levels of hsCRP were assessed at Wave 3. Latent-class analysis was used to determine trajectories of depression and general linear models to determine the association between depression trajectories and hsCRP. Finally, mediation analysis was performed to test mediation of lifestyle factors. Results: Persistently moderate to high depressive symptoms were associated with higher hsCRP levels. Results were unaltered when we adjusted for demographics and health variables. Smoking mediated the association between depressive symptoms total score and hsCRP, in large part. Persistently higher scores on somatic and cognitive symptom subscales were associated with higher levels of hsCRP than persistently low scores. These results were rendered nonsignificant after covariate adjustment. Conclusion: Persistent depressive symptoms were associated with subsequent higher levels of hsCRP, with somatic and cognitive symptoms contributing equally. The association was mediated by smoking behavior. These findings suggest that reducing adolescent depression and smoking are important starting points in the prevention of inflammatory diseases