Prevalence and clinical correlates of irritability in major depressive disorder: a preliminary report from the Sequenced Treatment Alternatives to Relieve Depression study.

BACKGROUND: Irritability is a common feature of major depressive disorder (MDD), though it is not included in the DSM-IV diagnostic criteria for adult MDD and is not assessed in most standard depression rating scales. Irritability with or without depression has been associated with risk for suicide, violence, and cardiovascular disease.
METHOD: The prevalence of significant levels of irritability was examined among the first 1456 outpatients with nonpsychotic MDD entering the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study. Sociodemographic and clinical features were compared for participants who did and did not report irritability at least 50% of the time during the week preceding study entry.
RESULTS: Of 1456 evaluable subjects, 582 (40%) reported irritability more than half the time. These individuals were more likely than nonirritable subjects to be female, to be younger, to be unemployed, and to report a history of at least 1 suicide attempt. Functional status and quality of life were also poorer in this group. Irritability was correlated with overall depressive severity, which accounted for nearly all of the clinical differences noted, with the exception of vascular disease, for which the association persisted after controlling for age, sex, and depressive severity.
CONCLUSION: Irritability is prevalent among depressed outpatients and associated with a greater likelihood of suicide attempts, poorer functional status, and greater prevalence of vascular disease. It is correlated with overall depression severity and thus may not represent a distinct depressive subtype per se. The impact of irritability on course and treatment outcome merits further study.