A Systematic Review of Long-Interval Intracortical Inhibition as a Biomarker in Neuropsychiatric Disorders.

Long-interval intracortical inhibition (LICI) is a paired-pulse transcranial magnetic stimulation (TMS) paradigm mediated in part by gamma-aminobutyric acid receptor B (GABAB) inhibition. Prior work has examined LICI as a putative biomarker in an array of neuropsychiatric disorders. This review conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) sought to examine existing literature focused on LICI as a biomarker in neuropsychiatric disorders. There were 113 articles that met the inclusion criteria. Existing literature suggests that LICI may have utility as a biomarker of GABAB functioning but more research with increased methodologic rigor is needed. The extant LICI literature has heterogenous methodology and inconsistencies in findings. Existing findings to date are also non-specific to disease. Future research should carefully consider existing methodological weaknesses and implement high-quality test-retest reliability studies.

Improvement in hypersomnia with high frequency repetitive transcranial magnetic stimulation in depressed adolescents: Preliminary evidence from an open-label study.

STUDY OBJECTIVES: Sleep disruption is a significant symptom of major depressive disorder (MDD). To our knowledge, no prior work has examined the impact of repetitive transcranial magnetic stimulation (rTMS) on sleep disturbances in adolescents with MDD. METHODS: Seventeen adolescents with treatment-resistant depression received 30 daily sessions of 10-Hz rTMS applied to the left dorsolateral prefrontal cortex (L-DLPFC). Clinical symptoms were assessed at baseline; after 10, 20, and 30 treatments; and at a 6-month follow-up visit. Insomnia was measured with a 3-item subscale of the Quick Inventory of Depressive Symptomatology-Adolescent (17 Item)-Self Report (QIDS-A17-SR). Hypersomnia was measured with a single QIDS-A17-SR item. Depression severity was rated with the Children's Depression Rating Scale, Revised (CDRS-R). The effect of rTMS on sleep was examined via linear mixed model analyses, with fixed effects of time (as a proxy of treatment), depression severity, age, and hypnotic medication use. RESULTS: No significant main effect of time was observed on the insomnia subscale (F4,43.442 = 1.078, p = 0 .379). However, there was a significant main effect of time on the QIDS-A17-SR hypersomnia score (F4,46.124 = 2.733, p = 0 .040), with significant improvement from baseline to treatment 10 (padj = 0.019) and from baseline to 6-month follow-up (padj = 0.044). In exploratory sensitivity analyses, response/nonresponse to rTMS for overall depressive symptoms had no significant effect on sleep outcomes. CONCLUSIONS: rTMS may have intrinsic effects on hypersomnia apart from its antidepressant effects in depressed adolescents. Future work should utilize sham controls and objective, quantitative measurements of sleep architecture to assess effects of rTMS in depressed adolescents. CLINICAL TRIAL REGISTRY: Clinicaltrials.gov identifiers are NCT00587639, NCT01502033, NCT01804270.