The exact causes of depression are unknown. At the same time, certain events may trigger the disease. Stressful life events and trauma Many life changes can trigger episodes of depression. Unresolved childhood trauma and sexual and physical abuse are catalysts for depressive episodes. Genetics A family history of depression or other mood disorders, such as bipolar disorder or seasonal affective disorders, increases depressive disorder. Stressful life events and trauma Many life changes can trigger episodes of depression. Unresolved childhood trauma and sexual and physical abuse are catalysts for depressive episodes. Aging As you age, changes in your brain chemistry may make you more susceptible to depression. Changes in your hormone levels around menopause or after a hysterectomy also increase your risk of developing depression. Health conditions Depression is also associated with several medical conditions such as cancer, heart disease, Parkinson's disease and stroke. Chemical imbalances in the brain Depression is a mental state that can be caused by an imbalance of chemicals in your brain. The exact cause is unknown, although it involves several neurotransmitters (chemicals that relay signals from one nerve cell to another). A decreased amount of the chemical serotonin in the brain causes increased activity in specific brain parts, leading to anxiety and sadness. Other causes of depression include: Side effects of medications Certain prescription drugs, such as steroids and some pain medications, can cause depression. Gender