Irritability as a symptom of major depression

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Molecular Psychiatry advance online publication 10 March 2009; doi: 10.1038/mp.2009.20

The importance of irritability as a symptom of major depressive disorder: results from the National Comorbidity Survey Replication

M Fava¹, I Hwang², A J Rush^3,4, N Sampson², E E Walters² and R C Kessler²

1. Department of Psychiatry, Massachusetts General Hospital, Boston, MA, USA
2. Department of Health Care Policy, Harvard Medical School, Boston, MA, USA
3. Department of Psychiatry, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA
4. Department of Clinical Sciences, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA

Correspondence: Dr R Kessler, Department of Health Care Policy, Harvard Medical School, 180 Longwood Ave, Boston, MA 2115, USA. E-mail: kessler@hcp.med.harvard.edu

Received 24 June 2008; Revised 27 January 2009; Accepted 28 January 2009; Published online 10 March 2009.

Abstract

Irritability is a diagnostic symptom of major depressive disorder (MDD) in children and adolescents but not in adults in both the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) and International Classification of Diseases (ICD-10) systems. We explore the importance of irritability for subtyping adult DSM-IV MDD in the National Comorbidity Survey Replication (NCS-R), a national US adult household survey. The WHO Composite International Diagnostic Interview (CIDI) was used to assess prevalence of many DSM-IV disorders in the lifetime and in the year before interview (12-month prevalence). MDD was assessed conventionally (that is, requiring either persistent sadness or loss of interest), but with irritability included as one of the Criterion A symptoms. We also considered the possibility that irritability might be a diagnostic symptom of adult MDD (that is, detect cases who had neither sad mood nor loss of interest). Twelve-month MDD symptom severity was assessed with the Quick Inventory of Depressive Symptomatology and role impairment with the Sheehan Disability Scale. After excluding bipolar spectrum disorders, irritability during depressive episodes was reported by roughly half of respondents with lifetime DSM-IV MDD. Irritability in the absence of either sad mood or loss of interest, in comparison, was rare. Irritability in MDD was associated with early age of onset, lifetime persistence, comorbidity with anxiety and impulse-control disorders, fatigue and self-reproach during episodes, and disability. Irritability was especially common in MDD among respondents in the age range 18–44 and students. Further investigation is warranted of distinct family aggregation, risk factors and treatment response. Consideration should also be given to including irritability as a nondiagnostic symptom of adult MDD in DSM-V and ICD-11.