Researchers don’t know the exact cause of depression. They think that several factors contribute to its development, including: Brain chemistry: An imbalance of neurotransmitters, including serotonin and dopamine, contributes to the development of depression. Genetics: If you have a first-degree relative (biological parent or sibling) with depression, you’re about three times as likely to develop the condition as the general population. However, you can have depression without a family history of it. Stressful life events: Difficult experiences, such as the death of a loved one, trauma, divorce, isolation and lack of support, can trigger depression. Medical conditions: Chronic pain and chronic conditions like diabetes can lead to depression. Medication: Some medications can cause depression as a side effect. Substance use, including alcohol, can also cause depression or make it worse.