The terms "nervous breakdown" and "mental breakdown" have not been formally defined through a diagnostic system such as the DSM-IV or ICD-10, and are nearly absent from current scientific literature regarding mental illness. Although "nervous breakdown" does not necessarily have a rigorous or static definition, surveys of laypersons suggest that the term refers to a specific acute time-limited reactive disorder, involving symptoms such as anxiety or depression, usually precipitated by external stressors.
Specific cases are sometimes described as a "breakdown" only after a person becomes unable to function in day-to-day life.
Causes of such breakdowns are varied. A 1996 study found that problems with intimate relationships, such as divorce or marital separation, contributed to 24% of nervous breakdowns. Problems at work and school accounted for 17% of cases, and financial problems for 11%. Though in themselves, nervous breakdowns are considered a "health problem" by most professionals, surveys suggest that in the United States, health problems have decreased in importance as a contributor to nervous breakdowns. Health problems accounted for 28% of nervous breakdowns in 1957, 12% in 1976, and only 5.6% in 1996.
Similar disorders 
Rapport, Todd, Lumley, and Fisicaro suggest that the closest DSM-IV diagnostic category to nervous breakdown is Adjustment Disorder with Mixed Anxiety and Depressed Mood (Acute). Adjustment disorders and nervous breakdowns are both acute reactions to stress that resolve after removal of the stressor. However, DSM-IV excludes from adjustment disorders cases secondary to bereavement, which contributes to approximately 6-8% of nervous breakdowns.
Nervous breakdowns may share some features of acute stress disorder and post-traumatic stress disorder, in that these each occur in response to an external stressor, and may be marked with sleep disturbance, diminished concentration, and mood lability. However, the symptoms of nervous breakdown do not include the constellation of re-experienced trauma, dissociation, avoidance, and numbing of general responsiveness that are associated with the other two disorders, and the types of stressors linked to a nervous breakdown are generally less extreme.
Nervous breakdowns may share many features of mixed anxiety-depressive disorder (MADD). However, the definition of MADD suggests a chronic condition, in contrast to the acute, short-term nature of a nervous breakdown.
See also 
- Panic attack
- Adjustment disorder
- Causes of mental disorders
- Mental health
- Psychotic break
- Rapport, L. J.; Todd, R. M.; Lumley, M. A.; Fisicaro, S. A. (1998). "The diagnostic meaning of "nervous breakdown" among lay populations". J Pers Assess 71 (2): 242–252. doi:10.1207/s15327752jpa7102_11.
- Mayo Clinic Mental Breakdown
- Hallowell, Edward M & John Ratey. 2005. Delivered from Distraction: Getting the Most out of Life with Attention Deficit Disorder. Ballentine Books. ISBN 0-345-44231-8
- Swindle, R., Jr.; Heller, K.; Pescosolido, B.; Kikuzawa, S. (2000). "Responses to nervous breakdowns in America over a 40-year period. Mental health policy implications". Am Psychol. 55 (7): 740–749. doi:10.1037/0003-066X.55.7.740. PMID 10916863.