Many patients and families are particularly concerned about whether depression is hereditary. The prevalence of depression in relatives is much higher than in the general population, and the closer the blood relationship the higher the prevalence, with about 1/4 of patients having a family history of depression. Stressful events can induce pathogenic gene expression, and in the presence of stress, a person’s genetic background will determine whether he or she will have a depressive episode. In layman’s terms, if a person has a family history of depression, he or she may not necessarily get depressed, but the risk of getting depressed is higher than others, and if he or she encounters a very stressful life event, the “time bomb” may be set off.