Bipolar disorder (BD) is frequently misdiagnosed as major depressive disorder (MDD), which may lead to inappropriate treatment and poor outcomes. This study aimed to compare demographic and clinical features between patients with MDD and those with BD, but being misdiagnosed as MDD, in China.
A total of 1487 patients diagnosed with MDD were consecutively evaluated in 13 psychiatric hospitals or psychiatric units of general hospitals nationwide in China. The patients' sociodemographic and clinical characteristics were recorded using a standardized protocol and data collection procedure. The Mini-International Neuropsychiatric Interview (MINI) was used to establish DSM-IV diagnoses, and identify patients with MDD and those with BD, but being misdiagnosed with MDD.
The proportions of BD (all types), bipolar I disorder (BD-I), and bipolar II disorder (BD-II) misdiagnosed as MDD in clinical practice were 20.8%, 7.9%, and 12.8%, respectively. Multiple logistic regression analyses revealed that compared to MDD patients, BD-I was characterized by more atypical depressive features (increased appetite, increased sleep, and weight gain) [odds ratio (OR) = 2.0, 95% confidence interval (CI): 1.2–3.2], more psychotic symptoms (OR = 2.1, 95% CI: 1.3–3.5), more lifetime depressive episodes (OR = 1.1, 95% CI: 1.1–1.2), and earlier age of onset (OR = 0.97, 95% CI: 0.9–0.99); BD-II was characterized by more psychotic symptoms (OR = 2.1, 95% CI: 1.4–3.1) and earlier age of onset (OR = 0.96, 95% CI: 0.9–0.97). In addition, compared to BD-II patients, BD-I patients were characterized by more frequent depressive episodes per year (OR = 3.1, 95% CI: 1.5–6.6).
Depressive episodes in the context of BD-I and BD-II, among those who were misclassified as MDD, present some different clinical features compared to MDD. This finding should be taken into account in guiding diagnostic practices in China.