Treating refractory depression in Parkinson’s disease: a meta-analysis of transcranial magnetic stimulation

BACKGROUND: Parkinson’s disease (PD) is often accompanied by clinically identified depression. Providing effective pharmacotherapies that concomitantly treat both motor and psychological symptoms can pose a challenge to physicians. For this reason, alternatives to standard anti-depressant treatments, such as repetitive transcranial magnetic stimulation (rTMS), have been evaluated within the Parkinson’s population. METHODS: A literature search was conducted on the PubMed database for all studies that evaluated rTMS as a treatment in patients with both depression and PD. A meta-analysis was performed on all studies that reported mean pre- and post-rTMS depression inventory scores. Widely used depression inventories included both self-report and clinician-administered measures. Effect size for individual study groups and across all studies was calculated. RESULTS: Six of 7 studies meeting inclusion criteria reported significantly improved depression scores, large effect sizes, and significant p-values. Total weighted average effect size was calculated at 1.32 across all study groups that applied rTMS. CONCLUSIONS: Across all but one study, rTMS appears to effectively reduce depression scores among self-reported and clinician administered inventories. The total weight average effect size showed that, when considering study sample sizes and degree of findings, this form of neurostimulation can relieve PD patients of their depressive symptoms. Further, rTMS is a promising alternative to traditional anti-depressant therapies when treating refractory depression in patients with PD.