Non-invasive brain stimulation for suicidal ideation: a systematic review and metanalysis of the current literature

Data suggests that the available therapeutic tools are still insufficient to deal with suicidality. Non-Invasive Brain Stimulation techniques (NIBS) have entered the recognized guidelines for therapies in psychiatry due to the advantages related to safety and tolerability. The purpose of this review and meta-analysis is to assess if and how NIBS techniques are used and could be effective in the treatment of suicidal ideation. The search included the Scopus, Pubmed, and Web of Science databases. The word "suicide" was combined with "NIBS", "transcranial magnetic stimulation" (TMS), "deep TMS" and "transcranial direct current stimulation". Nine studies met the inclusion criteria and were included in the review. High frequency repetitive TMS (rTMS) protocols were associated with a significant reduction in suicidal ideation, with individual studies reporting improvements ranging from 20% to over 35% on scales such as the scale for suicide ideation (SSI) and the Beck scale of suicide ideation (BSI) (p < 0.01; p < 0.01; p < 0.001). The meta-analysis showed that active rTMS significantly reduced suicidal ideation compared to sham control conditions (Z = 16.79, p < 0.0001). Heterogeneity was high (I-2 = 99%, chi-square = 473.22, df = 3, p < 0.0001). High frequency rTMS protocols appeared most effective; deep TMS (dTMS) showed mixed results, and only one study utilized transcranial direct current stimulation (tDCS). Due to limited data, no meta-analysis was conducted on dTMS or tDCS studies. Although preliminary findings suggest a potential for NIBS techniques to reduce suicidal ideation, the current evidence is limited by the small number of high-quality studies and heterogeneity in the protocols and outcomes. Therefore, conclusions regarding clinical efficacy should be considered tentative.