Others seem to become depressed for no clear reason. It appears to be caused by a combination of genetic, biological, and psychosocial factors. Sometimes, people develop depression as a result of taking certain medications or with certain illnesses. Some drugs used to treat arthritis, heart problems, high blood pressure, and cancer can produce depression. The effects of these drugs may not always be clear right away.
Scientists also think that some illnesses themselves can bring about depression.
These include Parkinson's disease, stroke, and hormonal disorders such as thyroid disease. Genetics, too, can play a role. Studies show that some forms of depression run in families. Children of depressed parents may be at a higher risk of getting the disease themselves. Depression is the most treatable of all mental illnesses.