The depression is a repeating disease and even often recurrent. The risk to remake a depressive episode after a first depression is evaluated at 50 %. Why a depressive relapse? How to prevent it? Which strategies to set up? Answers by the service of adult psychiatry and example of a group therapy based on the cognitive therapy and exercises of meditation, created by the department of psychiatry to prevent the depressive relapses among high-risk patients. Among the old persons, which age brackets are more at the risk and why? Answers to the service of geriatric psychiatry.