"If you could prevent an episode of depression, would you? Preventing depression has traditionally been hard to do, because it's hard to predict who will get depressed and when. But recent studies have shown that carefully timed treatments targeted at specific high-risk groups can prevent depressive episodes. These groups include patients with diabetes and who have had major depression in the past, people with a pattern of seasonal depression and women at risk for postpartum depression. The preventive treatments were antidepressant medications in the first two studies and psychotherapy in the third."
"For those with one previous episode, the likelihood of major depression recurring is more than 50 percent, and more than 75 percent for those with two or more previous episodes. Anyone with two past episodes of depression should consider preventive treatment of some kind."