Transcranial Magnetic Stimulation Markers of Antidepressant Treatment in Adolescents with Major Depressive Disorder

Background: The goal of this study was to examine baseline transcranial magnetic stimulation measures of cortical inhibition and excitability in depressed patients and characterize their longitudinal posttreatment changes. Methods: Fifteen adolescents (age 13-17 years) with moderate to severe major depressive disorder and 22 healthy controls (age 9-17) underwent single- and paired-pulse transcranial magnetic stimulation and clinical assessments. Transcranial magnetic stimulation measures included short-interval intracortical inhibition (2 and 4 milliseconds), long-interval intracortical inhibition (100, 150, and 200 milliseconds), cortical silent period, and intracortical facilitation (10, 15, and 20 milliseconds). Ten participants with major depressive disorder initiated antidepressant treatment or had dose adjustments. These participants were reassessed after treatment. Depression symptom severity was measured with the Children's Depression Rating Scale, Revised. Robust regression modeling compared healthy and depressed adolescents at baseline. Relationships between changes in cortical inhibition and changes in depressive symptom severity were assessed in the depressed adolescents receiving antidepressant treatment. Results: Our results revealed that at baseline, short-interval intracortical inhibition-2 was significantly reduced (P_adj =. 01) in depressed participants, suggesting impaired cortical inhibition compared with healthy controls. At follow-up, improvement in Children's Depression Rating Scale, Revised scores correlated with improvement in short-interval intracortical inhibition-4 amplitude (greater inhibition) after antidepressant treatment (R² = 0.63; P =. 01). Conclusions: These results suggest that cortical inhibition measures may have promise as biomarkers in adolescents treated for depression.