BACKGROUND: Past research suggests that individuals suffering from depressive disorders with bipolar features might have different clinical outcomes resembling bipolar disorders. The objectives of this study are to determine the prevalence of bipolar features among individuals meeting the criteria for 12-month major depressive disorder (MDD) in the Iranian population and to examine the demographic and clinical characteristics associated with these features.
METHODS: Data were drawn from the Iranian Mental Health Survey (IranMHS), a representative household survey of the Iranian population aged 15-64 years. The study sample consisted of all individuals with a 12-month MDD (n = 1014) ascertained by the Composite International Diagnostic Interview (CIDI 2.1) without a lifetime history of bipolar I or II disorders. Mood Disorder Questionnaire (MDQ) was used to screen for the lifetime history of bipolar features among participants with MDD.
RESULTS: Among participants meeting the 12-month MDD criteria, 22.1% (95% CI: 19.6-24.7) had a lifetime history of bipolar features. Compared with those without these features, participants with bipolar features had higher odds of endorsing suicidal ideations and suicide attempts, comorbid anxiety and substance use disorders, severe impairment, history of psychotic symptoms, some features of atypical depression and fewer depressive symptoms. Associations with comorbid anxiety disorders [Odds Ratio (OR) = 1.43; 95% confidence interval (CI): 1.00-2.03] and history of psychotic symptoms (OR = 2.63 95% CI: 1.81-3.81) persisted in multivariable models. LIMITATION: Relying on self-reports of lifetime bipolar symptoms which is open to recall bias, and cross-sectional study design which limits interpretation of outcome and course of MDD are two major limitations of this study.
CONCLUSION: The presence of bipolar features is associated with a distinct demographic and clinical profile in MDD. Identifying these cases would enhance the homogeneity of the depressive disorder phenotype in general population surveys. Identifying MDD patients with these features has potential clinical implications.