Undiagnosed bipolar disorder in patients treated for major depression in China

Abstract Background Bipolar disorder (BD) is a recurrent, complex illness and often misdiagnosed and treated as a major depressive disorder (MDD). This study set out (1) to investigate the proportion of BD in patients treated for MDD using DSM-IV diagnostic criteria; (2) to test the usefulness of the screening tool — the 32-item Hypomania Checklist (HCL-32) in Chinese patients; and (3) to assess whether MDD patients with subthreshold manic features (patients who screened positive for BD on the HCL-32, but did not meet the diagnostic criteria for DSM-IV BD as measured by Mini International Neuropsychiatric Interview (MINI)) differ from those with BD, and from those suffering from MDD without manic features in terms of basic demographic and clinical variables. Methods A total of 1487 patients treated for MDD were consecutively examined in 13 mental health centers in China. The patients' socio-demographic and clinical characteristics were recorded using a standardized protocol and data collection procedure. The HCL-32 was self-completed by patients to identify hypomanic symptoms, and the MINI was used by clinicians to establish DSM-IV diagnoses. Results The proportions of undiagnosed BD (all types), BD-I and BD-II were 20.8%, 7.9% and 12.8%, respectively. The HCL-32 had low positive predictive value (0.43). Compared to MDD patients without subthreshold manic features, MDD patients with subthreshold manic features were younger at onset, less likely to be married and had more depressive episodes on a seasonal basis, and more frequent depressive episodes overall. Compared to BD patients, MDD patients with subthreshold manic features had an older age at onset and less frequent depressive episodes and less family history of psychiatric disorders, appetite, weight gain and time spent sleeping, suicide ideation and attempts and psychotic symptoms. Conclusions At least one fifth of Chinese patients treated for MDD may have an undiagnosed BD. The HCL-32 is useful to identify broader subthreshold bipolar features. The findings need to be confirmed by longitudinal studies using more comprehensive, standardized instruments.