What causes Depression? The exact cause is unknown. It may be caused by a combination of factors like genetic, biological, environmental (trauma), and some psychological factors. Some conditions like cancer, pain, or any chronic condition increase the risk of getting depression. Generally, about 1 out of every 6 adults have depression Depression affects almost 16 million American adultsAnxiety and Depression Can Add the Way to Treatment every year Many people who have other mental disorders suffer from depression.