Depression is a medical illness that negatively affects how you feel, the way you think, and how you act. There are more than 3 million US cases per year. Possible causes of depression include a combination of biological, psychological, and social sources of distress. Research suggests these factors may cause changes in brain function, including the altered activity of certain neural circuits in the brain. Symptoms include sadness, sleep & appetite changes, and lack of motivation and energy.
Depression is a treatable condition by a medical professional, which requires a medical diagnosis. Lab tests or imaging are rarely required. The mainstay of treatment is usually medication, talk therapy, or a combination of the two.