UNDERDIAGNOSED BIPOLAR II DISORDER IN PATIENTS TREATED FOR RECURRENT DEPRESSION

Abstract

Bipolar II disorder is often recognized only after years of treatment for recurrent depression because patients usually seek care during depressive episodes, whereas hypomania may be experienced as productivity, sociability, or transient improvement. This review aimed to analyze the mechanisms underlying underdiagnosis, clinical indicators of bipolarity, the role of screening instruments, and the therapeutic implications of misclassification. A narrative, critical, descriptive, and structured literature review was conducted through searches in PubMed/MEDLINE, SciELO, and the Virtual Health Library/LILACS, supplemented by clinical guidelines and diagnostic documents, in July 2026. The synthesis indicated that early onset, high recurrence, a family history of bipolar disorder, atypical features, mixed symptoms, an episodic course, and antidepressant-associated activation increase diagnostic suspicion, although no single marker confirms the diagnosis. Questionnaires such as the MDQ and HCL-32 may organize the assessment; however, their performance depends on the clinical setting, and they do not replace a longitudinal clinical interview, collateral information, and exclusion of differential diagnoses. Timely recognition therefore requires reconstruction of the temporal course of mood symptoms and systematic reassessment of patients with recurrent depression, particularly when treatment response is unstable or signs of hypomania are present.