Examining the overlap between bipolar disorder, nonaffective psychosis, and common mental disorders using latent class analysis

Background: While dimensional models of psychopathology have delineated two broad factors underlying common mental disorders-internalizing and externalizing-it is unclear where bipolar disorder and nonaffective psychoses fit in relation to this structure and to each other. Given their low prevalence rates in the general population, these disorders generally tend to be excluded from such models. The current study used the person-centered approach of latent class analysis (LCA) to evaluate this question. Sampling and Methods: LCA of diagnostic data from an epidemiological sample, the National Comorbidity Survey (n = 5,877), was undertaken. Diagnoses utilized in analyses included mania, nonaffective psychoses, specific phobia, social phobia, agoraphobia, panic disorder, major depression, dysthymia, generalized anxiety disorder, post-traumatic stress disorder, alcohol dependence, drug dependence, and conduct disorder. Results: Results indicated that a 5-class LCA model optimally fit the data. Four of the classes mirrored those found in dimensional models-a class with few disorders, and 3 others with primarily fear, distress, and externalizing disorders. However, the fifth class-which is not evident in dimensional models-was unique in that it was the only one in which individuals demonstrated significant probabilities of both manic episodes and nonaffective psychoses in addition to markedly high levels of internalizing and externalizing disorders. Conclusion: This finding has important implications for nosological classification of psychopathology.