Amental breakdown is an acute, time-limited mental disorder that manifests primarily as severe stress-induced depression, anxiety, or dissociation in a previously functional individual, to the extent that they are no longer able to function on a day-to-day basis until the disorder is resolved.

A nervous breakdown is defined by its temporary nature, and often closely tied to psychological burnout, severe overwork, sleep deprivation, and similar stressors, which may combine to temporarily overwhelm an individual with otherwise sound mental functions.