Assessment of depressive symptom severity among patients with co-occurring bipolar disorder and substance dependence

We examined a modified version of the Hamilton Depression Rating Scale (HDRS) among treatment-seeking patients with co-occurring bipolar disorder and substance dependence in order to elucidate key features of depression in this specific population of patients.

Patients with current bipolar disorder and substance dependence who were prescribed mood stabilizers (n=105) completed a 27-item version of the HDRS that was subjected to item and principal components analyses. Preliminary validity analysis consisted of comparing the derived total and component scores to the depressed mood indicators from the Addiction Severity Index (ASI).

Eleven items representing two related components labeled "melancholia" and "anxiety" were retained. The 11-item HDRS total and component scores were higher for those who reported serious depression, serious anxiety, cognitive problems, and suicidal ideation on the ASI than for those who did not report these problems.

We conducted the analyses with a relatively small sample of patients who were primarily white and were diagnosed with bipolar I disorder, thus limiting the generalizability of findings. Moreover, we obtained limited data regarding construct validity of the 11-item scale.

Our psychometric evaluation of the HDRS led us to retain 11 items representing primarily melancholic and neurovegetative symptoms of depression. These findings suggest that sample-specific item characteristics of the HDRS need to be evaluated prior to using this scale to assess depressive symptom severity among patients with complex diagnostic and treatment characteristics.