Background: Little is known about the longer-term effects of adjunctive benzodiazepines on symptom response during treatment in patients with bipolar disorders.
Methods: The study sample consisted of 482 patients with bipolar I or II disorder enrolled in a 6-month, randomized, multi-site comparison of lithium- and quetiapine-based treatment. Changes in clinical measures (BISS total and subscales, CGI-BP, and CGI-Efficacy Index) were compared between participants who did and did not receive benzodiazepine treatment at baseline or during follow-up. Selected outcomes were also compared between patients who did and did not initiate benzodiazepines during follow-up using stabilized inverse probability weighted analyses.
Results: Significant improvement in all outcome measures occurred within each benzodiazepine exposure group. Benzodiazepine users (at baseline or during follow-up) experienced significantly less improvement in BISS total, BISS irritability, and CGI-BP scores than did benzodiazepine non-users. There were no significant differences in these measures between patients who did and did not initiate benzodiazepines during follow-up in the weighted analyses. There was no significant effect of benzodiazepine use on any outcome measure in patients with comorbid anxiety or substance use disorders.
Limitations: This is a secondary analysis of data from a randomized effectiveness trial that was not designed to address differential treatment response according to benzodiazepine use.
Conclusions: Adjunctive benzodiazepines may not significantly affect clinical outcome in lithium- or quetiapine-treated patients with bipolar I or II disorder over 6 months, after controlling for potential confounding factors.
Keywords: Benzodiazepines; Bipolar disorder; Clinical outcome; Lithium; Quetiapine.
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