This article highlights current findings on the functional roles of somatostatin in local neuronal circuits, and reviews somatostatin deficits across neurological disorders, including neuropsychiatric disorders [e.g., major depressive disorder (MDD), bipolar disorder, schizophrenia], and neurodegenerative disorders (e.g., Parkinson’s, Alzheimer’s, and Huntington’s diseases; Table 1). This evidence concerns the gene SST and major depressive disorder.