Patients with subthreshold bipolar disorder (sub-BP) experience severe clinical courses and functional impairments, which are comparable to those with bipolar I and II disorders (BP-I and -II). Nevertheless, lifetime prevalence, socioeconomic correlates and diagnostic overlaps of bipolar spectrum disorder (BPS) have not yet been estimated in the general population of South Korean adults.

This study aimed to estimate the lifetime prevalence, correlates and diagnostic comorbidities of BPS using a validated screening instrument in the nationwide general population of South Korea.

A total of 3013 adults among the 2011 Korean Epidemiologic Catchment Area survey (KECA-2011) completed face-to-face interviews using the Korean versions of the composite international diagnostic interview 2.1 and mood disorder questionnaire (K-CIDI and K-MDQ).

The lifetime prevalence of BPS in the South Korean adults was measured to be 4.3% (95% CI 2.6–6.9). Nearly 80% of the subjects with BPS were codiagnosed with other DSM-IV nonpsychotic mental disorders: 35.4% (95% CI 24.2–48.5) for major depression and dysthymic disorder, 35.1% (95% CI 27.7–43.3) for anxiety disorders and 51.9% (95% CI 40.5–63.1) for alcohol and nicotine use disorders. Younger age (18–34 years) was the only sociodemographic predictor of BPS positivity (P = 0.014) and the diagnostic overlap patterns were different between men and women.

Positivity for BPS was estimated to be much greater than the prevalence of DSM-IV BP in South Korea. Most of the respondents with BPS were diagnosed with other major mental disorders and this might be related with mis and/or underdiagnosis of clinically relevant Sub-BP.

The authors have not supplied their declaration of competing interest.