Mental disorders are characterized by problems that people experience with their mind (thoughts) and their mood (feelings). They are not well understood in terms of their causes, but the symptoms of mental illness are scientifically valid and well known. Treatment — usually involving both psychotherapy and medication — for most types of mental illness and mental health concerns is readily available and, eventually, effective for most people.

The diagnostic criteria for mental disorders (also known as “mental illness”) are composed of symptom checklists that primarily are focused on a person’s behaviors and thoughts. These lists of symptoms have been summarized from current diagnostic criteria commonly used in the United States by mental health professionals (the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition). We’ve divided the disorders into three broad categories below: adult, childhood, and personality disorders; some disorders may fall under more than one category.