"Nervous breakdown" is a slang term that does not have a precise medical or scientific meaning. Even as slang, it is presently used infrequently. It was perhaps in more common usage during the middle part of the last century. Even then, it had a diffuse meaning that referred to a broad range of mental disorders. In general, though, "nervous breakdown" was taken to mean an acute mental disorder severe enough to result in problems with everyday functioning (such as work, school, homemaking, or other social obligations).

Also, the term implied that the acute mental disorder was occurring in relation to environmental stress (such as may occur at work, at school, within interpersonal relationships, or as a result of a catastrophic event). This concept encompassed a broad range of specific psychiatric conditions - including depressive episodes, manic episodes, psychotic episodes, panic attacks, adjustment disorders, acute stress disorder, and post-traumatic stress disorder.

Although, colloquially, people may still refer to a "nervous breakdown," it is more helpful to define specifically the type of acute psychiatric disturbance. That being said, those who consider themselves suffering from a "nervous breakdown" are likely to be in significant distress, and are also likely to have some form of acute mental disorder. Therefore, these individuals should see a physician as soon as possible.