Definitions of mental disturbance are based on symptoms. For example, depression is the summarizing name for a scope of symptoms. Depression per se is not the cause of depressive symptoms. There are many potential etiology of depression. Nutrition, lifestyle, sun exposure, family dynamics are all potential causes.
Anti-depressive medications are among one of the most common durgs that are over prescribed, along with anti-psychotics.
Anti-depressive and anti-psychotic drugs are not the cause of depressions. Unfortunately, family medicine and psychiatry practice overly rely on these medication.