Factorial structure and familial aggregation of the Hypomania Checklist-32 (HCL-32): Results of the NIMH Family Study of Affective Spectrum Disorders.

Background There is substantial evidence that bipolar disorder (BD) manifests on a spectrum rather than as a categorical condition. Detection of people with subthreshold manifestations of BD is therefore important. The Hypomania Checklist-32 (HCL-32) was developed as a tool to identify such people. Purpose The aims of this paper were to: (1) investigate the factor structure of HCL-32; (2) determine whether the HCL-32 can discriminate between mood disorder subtypes; and (3) assess the familial aggregation and cross-aggregation of hypomanic symptoms assessed on the HCL with BD. Procedures Ninety-six probands recruited from the community and 154 of their adult first-degree relatives completed the HCL-32. Diagnosis was based on semi-structured interviews and family history reports. Explanatory factor analysis and mixed effects linear regression models were used. Findings A four-factor (“Activity/Increased energy,” “Distractibility/Irritability”, “Novelty seeking/Disinhibition, "Substance use") solution fit the HCL-32, explaining 11.1% of the total variance. The Distractibility/Irritability score was elevated among those with BP-I and BP-II, compared to those with depression and no mood disorders. Higher HCL-32 scores were associated with increased risk of BD-I (OR = 1.22, 95%CI 1.14–1.30). The “Distractibility/Irritability” score was transmitted within families (β = 0.15, p = 0.040). However, there was no familial cross-aggregation between mood disorders and the 4 HCL factors. Conclusions Our findings suggest that the HCL-32 discriminates the mood disorder subtypes, is familial and may provide a dimensional index of propensity to BD. Future studies should explore the heritability of symptoms, rather than focusing on diagnoses. [ABSTRACT FROM AUTHOR]