Diagnosis of bipolar disorder and differential diagnosis from other conditions: a narrative review

Purpose: Bipolar disorder (BD) is characterized by alternating episodes of mania or hypomania and depression, resulting in substantial psychosocial impairment. Despite its clinical importance, BD is frequently underrecognized or misdiagnosed as major depressive disorder (MDD) or other psychiatric conditions. This review aims to summarize current diagnostic criteria, key clinical differentiating features, and validated assessment tools in order to enhance diagnostic accuracy and facilitate earlier recognition in clinical practice.Current concepts: The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR), and the International Classification of Diseases, 11th Revision, define mania and hypomania by abnormal mood elevation accompanied by increased activity or energy. Bipolar I disorder requires the presence of at least one manic episode, whereas bipolar II disorder requires both hypomanic and major depressive episodes. Cyclothymic disorder and broader bipolar spectrum concepts emphasize subthreshold or atypical presentations that may be overlooked by categorical diagnostic systems. Structured and self-report instruments, including the structured clinical interview for DSM-5-TR, mood disorder questionnaire, hypomania checklist-32, bipolar spectrum diagnostic scale, and Young mania rating scale, play an important role in standardized assessment and longitudinal monitoring.Discussion and conclusion: Accurate diagnosis of BD requires integration of structured diagnostic interviews, standardized rating scales, collateral information, and longitudinal clinical observation. The differential diagnosis from MDD, borderline personality disorder, attention-deficit/hyperactivity disorder, and schizophrenia depends on careful evaluation of episode duration, illness course, and associated functional impairment. Future diagnostic approaches may benefit from dimensional and personalized models incorporating biomarkers, neuroimaging, and digital phenotyping.