Epidemiological studies indicate that the majority of patients with bipolar disorder are diagnosed many years later. Unipolar depression represents the most frequent misdiagnosis.

This study aimed to examine the symptom profiles of depressed patients in order to identify clinical specificities of bipolar depression.

A total of 31 depressed patients were recruited from psychiatry outpatient department of Hedi Chaker university hospital in Sfax (Tunisia), during October and November 2016. Unipolar and bipolar patients were compared on a broad range of parameters, including sociodemographic and clinical characteristics. Depressive symptoms were rated using the Montgomery Asberg Depression Rating Scale (MADRS) and Bipolar Depression Rating Scale (BDRS).

The total sample comprised 31 patients with 16 men and 15 women. It involved 20 with unipolar depression and 11 with bipolar depression. Patients with bipolar depression had more family history of bipolar disorder (P = 0.037) and a triggering factor had been identified less often (P = 0.03). MADRS scores were similar in bipolar and unipolar patient (median score 28.22 versus 28.36; P = 0.964). BDRS scores were significantly higher in bipolar depressed patients (median score 33 versus 25; P = 0.01). The mixed subscale (item 16 to 20) scores were particularly higher (median 6 vs. 1.2; P ≤ 0.01) especially concerning irritability (P = 0.001). Increased motor drive (P = 0.004) and agitation (P = 0.008).

Our findings suggest that the presence of mixed symptoms is very important to recognize depressed patients as having a bipolar disorder. We also recommend routine use of the BDRS for patients presenting for treatment of depression.

The authors have not supplied their declaration of competing interest.