Carl Zimmer in The Switches That Can Turn Mental Illness On and Off:
"Our experiences can rewrite the epigenetic code, however, and these experiences can start even before we’re born. In order to lay down the proper pattern of epigenetic marks, for example, embryos need to get the raw ingredients from their mothers. One crucial ingredient is a nutrient called folate, found in many foods. If mothers don’t get enough folate, their unborn children may lay down an impaired pattern of epigenetic marks that causes their genes to malfunction. These mistaken marks might lead to spina bifida, a disease in which the spinal column fails to form completely."
He further explains some research which indicates "Child abuse may leave a mark on its victims in much the same way that parental neglect affects rat pups. Abuse seems to have altered the epigenetic marks in their hippocampi. As a result, they made fewer stress receptors on their neurons, which left them unable to regulate their stress hormones, leading to a life of anxiety. That extra stress may have played a part in their committing suicide." And "And the influence of environment doesn’t end with childhood. Recent work indicates that adult experiences can also rearrange epigenetic marks in the brain and thereby change our behavior. Depression, for example, may be in many ways an epigenetic disease. Several groups of scientists have mimicked human depression in mice by pitting the animals against each other. If a mouse loses a series of fights against dominant rivals, its personality shifts. It shies away from contact with other mice and moves around less. When the mice are given access to a machine that lets them administer cocaine to themselves, the defeated mice take more of it."
Another excellent article from Carl Zimmer. More links in his post in The Loom:
Epigenetics and the Brain: Woo-free Coolness.