Serotonin-dependent depression in Parkinson's disease: A role for the subthalamic nucleus?

► Depression is the most common neuropsychiatric co-morbidity in Parkinson's disease. ► Low 5-HT and altered basal ganglia activity may be critical to develop depression. ► STN DBS has shown to inhibit 5-HT neurotransmission in animal models. ► Inhibited 5-HT transmission may underlie STN DBS depressive-like side effects.