Cytokines and Depressive Symptoms Among Adolescents.

The study was cross-sectional, so it cannot show that cytokines cause depression or that depression causes cytokine changes. Only 83 adolescents were analysed, and only 8 screened positive for clinical depression, giving little power for the cutoff analyses. Depression was measured by self-report with the PHQ-9, not by clinician diagnosis. Cytokines were measured once from saliva, so they may not reflect ongoing inflammation. The models did not adjust for sex hormones, pubertal status, or physical activity, all of which can affect inflammation and mood. Race was excluded from final models because too few participants were in each racial group. The sample was recruited in one U.S. region, and the largest income group was $101,000 to $150,000 (42.0%), so it may not apply broadly. The authors note effect sizes were small.

The authors declared no conflicts of interest. The study was funded by the National Institutes of Health National Institute of Nursing Research.

Do not conclude that salivary cytokines can diagnose or guide treatment for adolescent depression. The study is cross-sectional, only 8 of 83 participants screened positive, and the reported associations do not show cause or clinical usefulness.