The Brain: The Switches That Can Turn Mental Illness On and Off | Genes & Health | DISCOVER Magazine
These studies hint at how experiences in youth can rewrite the epigenetic marks in our brains, altering our behavior as adults. Meaney and his colleagues cannot test this hypothesis by running similar experiments on humans, of course, but last year they published a study that came pretty close.
Meaney’s team examined 36 human brains taken from cadavers. Twelve of the brains came from people who had committed suicide and had a history of abuse as children. Another 12 had committed suicide without any such history. The final 12 had died of natural causes. The scientists zeroed in on the cells from the hippocampi of the cadavers, examining the switch for the stress hormone gene they had studied in rats. Meaney and his colleagues found that the brains of people who had experienced child abuse had relatively more methyl groups capping the switch, just as the researchers had seen in rats that had not been licked much as pups. And just as those rats produced fewer receptors for stress hormones, the neurons of the people who had suffered child abuse had fewer receptors as well.