Objective: To determine the prevalence of unrecognized bipolar disorder and explore the clinical features of outpatients with depressive disorder associated with bipolar disorder.

Materials and Methods: The present study was a cross-sectional study. One hundred six volunteer participants, diagnosed with depressive disorder at Naresuan University Hospital, Buddhachinaraj Phitsanulok Hospital, and Phichit Hospital participated in this study. Psychiatrists interviewed the participants to collect basic data and clinical characteristics to determine unrecognized bipolar disorder using the Thai version of the Mini International Neuropsychiatric Interview (MINI).

Results: The results showed that the prevalence of unrecognized bipolar disorder was 18.9%. When multivariable logistic regression was used, it was found that there were two statistically significant factors associated with unrecognized bipolar disorder. These factors were a history of self-harm or suicide attempts (AOR 4.40, 95% CI 1.24 to 15.60), and atypical depression seen with overeating and hypersomnia (AOR 11.73, 95% CI 2.32 to 59.35).

Conclusion: There are several misdiagnoses of patients with bipolar disorder because the patients are usually in a depressive state when they decide to consult a doctor. Therefore, doctors should further probe especially in patients with atypical depression, history of self-harm or attempted suicide.

Keywords: Bipolar depression; Bipolar disorder; Diagnosis; Epidemiology; Prevalence

DOI: doi.org/10.35755/jmedassocthai.2021.11.13102

Received 29 June 2021 | Revised 6 October 2021 | Accepted 6 October 2021