Efficacy and placebo response of repetitive transcranial magnetic stimulation for primary insomnia

Repetitive transcranial magnetic stimulation (rTMS) has been considered a promising technique for the treatment of primary insomnia. However, its efficacy and placebo response remains unclear due to limited clinical data. Therefore, we conducted a systematic review to examine the efficacy and placebo response of rTMS. We performed a comprehensive literature search for clinical trials evaluating the efficacy of rTMS addressing primary insomnia. To pool effect size estimates (Hedges' g) of active rTMS and sham rTMS across studies for outcome measures, a meta-analysis was done according to the Cochrane guideline. In sum, rTMS significantly improved insomnia symptoms in the active rTMS group, and the pooled effect size of Pittsburgh Sleep Quality Index (PSQI) was −0.98 (95% CI: −1.28, −0.68) for treatment duration of 10 days, −1.16 (95% CI: −1.51, −0.82) for 20 days, and −2.14 (95% CI: −2.45, −1.83) for 30 days, respectively. However, the placebo response was also significant, reducing insomnia symptoms in the sham rTMS group. Furthermore, 73.5% (95% CI: 50.8%, 96.2%) of the effect size of active rTMS was actually produced by sham rTMS. The rTMS was effective in the treatment of primary insomnia, yet, the placebo effect of sham stimulation was highly significant. This new evidence may alter rTMS regimen for insomnia from a clinical and methodological point of view. Finally, in future research more objective data and multicenter double-blinded controlled studies should be encouraged. •rTMS was effective in the treatment of primary insomnia.•The effect size of rTMS increased with the increase of treatment duration within 30 days.•Majority of the effect size in active rTMS was produced by sham rTMS.