Preliminary evidence of an association between increased cortical inhibition and reduced suicidal ideation in adolescents treated for major depression

Background: Suicide is a leading cause of death among youth. Prior research using transcranial magnetic stimulation (TMS) has implicated deficits in GABAergic cortical inhibition in adolescent suicidal behavior, yet no studies have assessed whether cortical inhibition varies over time in conjunction with changes in suicidal ideation (SI). This study examined dynamic changes in long-interval intracortical inhibition (LICI), a TMS measure of GABA(B)-mediated inhibition, and their relationship with changes in SI in a small sample of adolescents undergoing pharmacologic treatment for depression. Methods: Ten depressed adolescents (aged 13-17) underwent clinical assessment and TMS testing at baseline and again at follow-up. All were treated with antidepressant medication in the interim. SI was measured with the Columbia Suicide Severity Rating Scale (C-SSRS) Intensity of Ideation subscale. LICI was measured at inter stimulus intervals of 100 and 150 ms. Results: There was a significant partial correlation, controlling for change in depression severity, between Delta LICI-100 and change in SI as measured by Delta C-SSRS (rho =.746, df = 7, p =.021), which remained after also controlling for time to follow-up assessment (rho =.752, df = 6, p =.032). No significant correlation was observed between Delta LICI-150 and change in SI. Limitations: Sample size; variable follow-up interval; inability to control for age, sex, and potential treatment effects. Conclusions: These data offer preliminary signal of an association between increases in GABA(B)-mediated cortical inhibition and reduction in SI over time in adolescents treated for depression. Further studies are warranted to explore the role of cortical inhibition in adolescent suicidal ideation and behavior.