Interaction Effect of Serum Serotonin Level and Age on the 12-Week Pharmacotherapeutic Response in Patients With Depressive Disorders
Abstract Despite the recognized antidepressant role of serotonin (5-hydroxytryptamine [5-HT]) signaling pathways in the central nervous system, the association between baseline peripheral 5-HT level and the antidepressant treatment response in clinical studies remains debatable. We investigated the individual and interaction effects of baseline serum 5-HT level and age on 12-week remission in outpatients with depressive disorders who received stepwise antidepressant treatment. Baseline serum serotonin levels were measured and the age of 1,094 patients recorded. The patients received initial antidepressant monotherapy; then, patients with an insufficient response or who experienced uncomfortable side effects received alternative treatments every 3 weeks (3, 6, and 9 weeks). Subsequently, 12-week remission, defined as a Hamilton Depression Rating Scale (HAMD) score of ≤ 7, was evaluated. Individual and interaction effects of serum 5-HT level (lower vs. higher based on the median value of 72.6 ng/mL) and age (< 60 vs. ≥ 60 years) on 12-week remission were analyzed using logistic regression models after adjusting for relevant covariates. Significant individual effects of serum 5-HT level and age on 12-week remission were not observed. However, a higher 5-HT level and age ≥ 60 years were significantly associated with higher 12-week remission rates. Our study suggests that the combination of baseline serum 5-HT level and age can be a useful predictor of 12-week antidepressant treatment outcomes.