Depression and Anxiety Following Deep Brain Stimulation in Parkinson's Disease: Systematic Review and Meta-Analysis

Introduction: Deep brain stimulation (DBS) is effective in advanced Parkinson's disease (PD), improving motor symptoms, fluctuations and quality of life. However, adverse psychiatric outcomes have been reported, albeit variably and in an unstandardized fashion. We aimed to summarize the published evidence on the outcomes of anxiety and depressive symptoms in Parkinson's disease patients following DBS, through systematic review and meta-analysis. Material and Methods: PubMed was searched until May 2012 to identify studies assessing anxiety and depressive symptoms in PD patients who underwent bilateral DBS of the subthalamic nucleus (STN) or globus pallidus internus (GPi). Random effects meta-analyses were conducted for groups of at least three studies that were homogeneous regarding the design and the instruments used. Results: 63 references were selected; 98.4% provided data on depression, and 38.1% on anxiety assessment scales. Two studies did not discriminate the target; from the remaining 61 references, short-term evaluation was performed in 37 (60.7%), mid-term in 36 (59.0%) and long-term in 5 (8.2%). Data on pre to postop variation was available in 57 (93.4%) reports and 16 (26.2%) presented STN-DBS versus different comparison groups: GPi-DBS (n = 4 studies, 25.0%), eligible for surgery (n = 6, 37.5%), and medical treatment (n = 7, 43.8%). Discussion: Improvement of depression and anxiety is apparent after DBS, more pronounced in the short-term, an effect that seems to wane in later assessments. Concerning depression, STN-DBS shows superiority against medical treatment, but not when compared to eligible for surgery control groups. The opposite is apparent for anxiety, as results favor medical treatment over STN-DBS, and STN-DBS over eligible for surgery control group. Superiority of one target over the other is not evident from the results, but data slightly favors GPi for both outcomes. Conclusion: The pattern and course of depressive symptoms and anxiety following DBS in PD is not clear, although both seem to improve in the short-term, especially depression following STN-DBS. Results are highly heterogeneous. Efforts should be carried out to standardize assessment procedures across centers.