Researchers have shown that changes in a type of brain cells called microglia underlie the depressive symptoms brought on by exposure to chronic stress. In animal experiments, the researchers were able to demonstrate that microglia-stimulating drugs served as effective and fast-acting antidepressants, producing complete recovery of the depressive-like behavioral symptoms and increasing neurogenesis to normal levels within days. This suggests new avenues for drug research, using microglia stimulators as antidepressants.