Psychometric evaluation of the DSM-IV criterion B mania symptoms in an Australian national sample

BACKGROUND: Although numerous studies have examined the latent structure of major depression, less attention has focused on mania. This paper presents the first investigation outside the USA to evaluate the psychometric properties of the DSM-IV criterion B mania symptoms using item response theory (IRT). METHOD: Data were drawn from the Australian 2007 National Survey of Mental Health and Well-Being (NSMHWB, n = 8841). The psychometric performance of the mania symptoms was evaluated using a two-parameter logistic model. Because substance use disorders (SUDs) frequently co-occur with mania and can influence manic symptom expression, differential item functioning (DIF) between mania respondents with/without a SUD diagnosis was also assessed. RESULTS: Factor analysis supported a unidimensional trait underlying mania. The grandiosity symptom displayed the highest discrimination whereas discrimination was lowest for decreased need for sleep. Relatively speaking, grandiosity tapped the severe end and increased goal-oriented activities tapped the mild end of the mania severity continuum. The symptoms generally performed equivalently between those with/without a SUD diagnosis, with one exception; the activities with painful consequences symptom was endorsed at lower levels of severity, and hence more frequently, by those with a SUD diagnosis versus those without a SUD diagnosis. CONCLUSIONS: Accurate conceptualization of latent structure has crucial theoretical, statistical and clinical implications. The symptoms generally performed well in distinguishing between respondents with differing levels of liability, but others did not, suggesting modification is warranted to ensure optimal use in epidemiological samples. Given the dearth of psychometric evaluation studies of mania, further research replicating these results is necessary.