Background There is considerable debate surrounding the effective measurement of DSM-IV symptoms used to assess manic disorders in epidemiological samples.Method Using two nationally representative datasets, the National Epidemiological Survey of Alcohol and Related Conditions (NESARC, n=43 093 at wave 1, n=34 653 at 3-year follow-up) and the National Comorbidity Survey - Replication (NCS-R, n=9282), we examined the psychometric properties of symptoms used to assess DSM-IV mania. The predictive utility of the mania factor score was tested using the 3-year follow-up data in NESARC.Results Criterion B symptoms were unidimensional (single factor) in both samples. The symptoms assessing flight of ideas, distractibility and increased goal-directed activities had high factor loadings (0.70-0.93) with moderate rates of endorsement, thus providing good discrimination between individuals with and without mania. The symptom assessing grandiosity performed less well in both samples. The quantitative mania factor score was a good predictor of more severe disorders at the 3-year follow-up in the NESARC sample, even after controlling for a past history of DSM-IV diagnosis of manic disorder.Conclusions These analyses suggest that questions based on some DSM symptoms effectively discriminate between individuals at high and low liability to mania, but others do not. A quantitative mania factor score may aid in predicting recurrence for patients with a history of mania. Methods for assessing mania using structured interviews in the absence of clinical assessment require further refinement.
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