Postmortem study finds adult neurogenesis stalls in depression

Soon after each donor's death, researchers examined the hippocampus—the brain region involved in episodic memory and emotional responses—from people with major depressive disorder and from control subjects. Across nearly half a million brain cells, the Columbia University team found that adult neurogenesis, the creation of new neurons, had stalled in the depressed group.

The result matters because the hippocampus is one of the few parts of the adult brain known to keep making neurons. Those cells are thought to support pattern separation: keeping a new experience distinct from older memories. When that process weakens, an ordinary event can take on the emotional weight of past rejection. Studies in mice link pattern separation to adult neurogenesis, and research involving brain-tumor patients has suggested a similar connection in people, but the human mechanism is not yet complete.

The study did not find an isolated defect. Researchers recorded gene activity and protein changes in individual cells and located those cells within the hippocampal circuit. They found altered programs involved in forming connections and communication between neurons, supplying cellular energy and moving cargo inside cells. The trisynaptic circuit, a key route for forming new emotional memories, also showed inflammation and cellular stress.

Some of the affected genes showed altered activity and have genetic variants associated with major depression; others showed epigenetic changes, molecular controls that can reflect influences such as stress, learning, aging or chemicals. Maura Dupont, the Columbia psychiatrist who led the research, said the breadth of the changes may indicate that depression is not one biological disease but several mechanisms grouped under one diagnosis.

Practically, the map gives researchers targets to test: restoring neurogenesis or repairing the surrounding hippocampal circuit could become one strategy for some patients. It does not yet establish that turning neurogenesis back on will relieve depression, and the measurements came from brain tissue collected after death. The advance is therefore a cellular atlas and a research guide, not a treatment available to patients.