Objective: To examine the occurrence of concomitant psychiatric disorders in patients with treatment-resistant unipolar and bipolar depression.
Method: Forty-nine patients participated as subjects. Twenty-four (49%) had unipolar depression and 25 (51%) had bipolar depression using DSM-III-R criteria. Structured clinical interviews were conducted with all patients. Chart reviews and interviews with family members were also carried out. Information relating to both current and lifetime diagnoses was obtained.
Results: Of the entire sample, 75.5% were found to have at least one other Axis I diagnosis and 46.9% had at least two additional Axis I diagnoses. The unipolar group had significantly more current comorbid diagnoses. When type of diagnoses was examined, unipolar patients had significantly more anxiety diagnoses at the time of the index episode, and over their entire lifetime. Bipolar patients had significantly more lifetime substance abuse diagnoses.
Conclusions: Axis I comorbidity appears to be differentially associated with treatment resistance in unipolar and bipolar depression.