Unipolar depression with bipolar family history: links with the bipolar spectrum

The aim of the present paper was to find if unipolar major depressive disorder (MDD) with bipolar family history could be included in the bipolar spectrum, by comparing it to unipolar MDD without bipolar family history, and to bipolar II disorder, on typical bipolar variables. A sample of 280 consecutive bipolar II outpatients, and a sample of 135 consecutive unipolar MDD outpatients, presenting for major depressive episode (MDE) treatment, were interviewed with the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders (4th edn). Hypomanic symptoms during the MDE were systematically assessed. Clinical variables used to validate the inclusion of unipolar MDD with bipolar family history in the bipolar spectrum were young age of onset, many MDE recurrences, atypical features, and depressive mixed state (DMX; an MDE plus >2 concurrent hypomanic symptoms), following many previous studies reporting that these variables were typical features of bipolar disorders. Means were compared by t-test and frequencies by chi2 test (stata 7). Two-tailed P < 0.05 was chosen. Unipolar MDD with bipolar family history was present in 20% of MDD patients. Comparisons among unipolar MDD with bipolar family history (UP+BPFH), unipolar MDD without bipolar family history (UP-BPFH), and bipolar II (BPII), found that UP+BPFH versus UP-BPFH had a significantly lower age, lower age of onset, fewer recurrences, and more DMX; that UP+BPFH versus BPII had no significant differences (apart from recurrences); and that UP-BPFH versus BPII had significantly different age, age of onset, recurrences, atypical features, and DMX. Findings suggest that UP+BPFH shows many bipolar signs, and that it could therefore be included in the bipolar spectrum. Unipolar MDD with bipolar family history had a clinically significant 20.0% frequency in the unipolar MDD sample, supporting the clinical usefulness of this depression subtype. The subtyping of MDD based on bipolar family history could have treatment implications.