Non-invasive brain stimulation for treating psychiatric symptoms in Parkinson's disease: A systematic review and meta-analysis.

Background: Non-invasive brain stimulation (NIBS), especially repetitive transcranial magnetic stimulation (rTMS), is a promising therapeutic tool for managing the psychiatric symptoms of Parkinson's disease (PD). This meta-analysis aims to assess the effect of NIBS on psychiatric symptoms in patients with PD.

Methods: Several electronic databases were systematically searched for relevant literature from inception to October 18, 2021. The therapeutic effects of NIBS were evaluated using a random-effects meta-analysis based on the standard mean difference (SMD) and multivariable-adjusted effect estimates and subgroup analyses. Publication bias and sensitivity analyses were used to explore the sources of heterogeneity.

Results: Finally, 57 and 15 studies with 4,010 participants were obtained from the meta-analysis and systematic review, respectively. Significant differences were found between NIBS and sham-stimulation/placebo participants for depression (SMD = -0.75, 95 % confidence interval [CI]: -0.99 to -0.50, I = 79 %), and rTMS combined with antidepressant therapy and antidepressant alone for depression (SMD = -0.98, 95 % CI: -1.37 to -0.59, I = 87 %) and anxiety (SMD = -1.46, 95 % CI: -2.44 to -0.48, I = 95 %). Meanwhile, lower risks were observed for post-treatment compared with pre-treatment for depression (relative risk [RR] = 0.66, 95 % CI: 0.57-0.76, I = 96 %) and anxiety (RR = 0.66, 95 % CI: 0.60-0.73, I = 67 %).

Conclusions: NIBS can be considered an effective non-pharmacological option for treating PD depression; moreover, rTMS combined with antidepressants was demonstrated to be a useful tool against depression and anxiety in PD.