Depression (major depressive disorder or clinical depression) is a serious mood disorder. It is one of the most common mental disorders in the U.S. It produces persistent and intense feelings of sadness and loss of interest for extended periods of time.[1] It causes severe symptoms that affect how you feel, think, and handle daily activities, such as sleeping, eating, or working. To be diagnosed with depression, the symptoms must be present for at least two weeks. Current research suggests that depression is caused by a combination of genetic, biological, environmental, and psychological factors.[2]
Untreated or undertreated MDD can result in serious problems and can render an individual disabled in his or her work life, family life, and social life.[3] Finding the right treatment for the individual patient is vital, and once an individual with MDD achieves stability with an antidepressant, he or she must be able to remain on his or her medication.
[1] https://www.mayoclinic.org/diseases-conditions/depression/symptoms-causes/syc-20356007; https://www.healthline.com/health/clinical-depression#whats-mdd.
[2] https://www.nimh.nih.gov/health/topics/depression/index.shtml
[3] https://www.webmd.com/depression/guide/untreated-depression-effects#2