The discovery, about a protein called fibroblast growth factor 9 or FGF9, goes against previous findings that depressed brains often have less of key components than non-depressed brains.
In this case, people with major depression had 32 percent more of FGF9 in hippocampus than people without the condition. The levels of several other fibroblast growth factors were down when FGF9 was up, suggesting that the entire system for regulating cell growth and development in the brains of depressed people was altered.
In rats, raising FGF9 levels artificially led to depression-like behavior changes, and repeated social stress caused brain FGF9 levels to rise.
Lowering FGF9 in the dentate gyrus using RNA interference caused levels of FGF9 to drop about 30 percent, while other FGF molecule levels stayed the same.and the rats showed less anxiety.
The researchers performing more experiments to determine why FGF9 production rises, as well as to study it in other brain regions and to see how it affects communication among brain cells.
The results were published in the journal Proceedings of the National Academy of Sciences.