Differentiating bipolar type I and II depression from unipolar depression: the role of clinical features, current symptoms and a past hypomanic symptoms checklist

Background: To explore the role of clinical features, current symptoms and a past hypomanic symptom checklist in distinguishing bipolar from unipolar depression among patients with current major depressive episodes. Method: Patients with bipolar I disorder (BDI, N=122), bipolar II disorder (BDII, N=160) as well as major depressive disorder (MDD, N=353) were enrolled. We collected clinical features and current symptoms on these patients, asked them to complete a 15-item checklist about prior symptoms of hypomania (HCL-15), and administered the Hamilton Depression Rating Scale. Results: Multivariate analyses showed that patients with BDI, compared with MDD, were less likely to be female and to endorse the symptoms of diminished interest; more likely to be obesity/overweight and to have more total episodes. Patients with BDII, compared with MDD again, were more likely to have an earlier age onset, more total episodes, more seasonal depressive onset, and to manifest irritable symptoms. Inclusion of HCL-15 in the comparison significantly increased the area under curve of BDII versus MDD. Conclusion: Our study suggests that clinical features and current symptoms could provide good ability in differentiating BDI from MDD. Combination of clinical features and the result of HCL-15may assist clinicians better to identify BDII.