Depression is a disease. It is not caused by personal weakness and is not a character flaw. When you have depression, chemicals in your brain called neurotransmitters are out of balance.
Most experts believe a combination of family history (your genes) and stressful life events may cause depression.
Sometimes even happy life events, such as a marriage or promotion, can trigger depression because of the stress that comes with change.
Just because you have a family member with depression or have stressful life events doesn't mean you'll get depression. You also may get depression without going through a stressful event.
Health problems also can cause depression. For example, both anemia and an underactive thyroid gland (hypothyroidism) can lead to depression. Treating the health problem usually cures the depression.
Certain medicines, such as steroids or narcotics, can cause depression. If you stop using the medicine, the depression may go away.