Prophylactic treatment response in bipolar disorder: results of a naturalistic observation study.

BACKGROUND: The objective of this study was to evaluate effectiveness of commonly used prophylactic treatments for bipolar disorder in a naturalistic setting and to explore factors associated with treatment response. METHODS: We reviewed charts of 120 patients with a confirmed diagnosis of bipolar I or bipolar II disorder. The sample consisted of 37 males and 83 females, in the age range of 20 to 81 years (mean age 45+/-14 years), treated at an outpatient psychiatry program in a teaching hospital. In contrast to controlled clinical trials, we did not exclude subjects with co-morbid conditions and/or substance abuse. Treatment outcome was evaluated using a scale for retrospective assessment of prophylactic treatment response. The scale rates the degree of improvement in the course of treatment weighted by the likelihood of response being attributable to the treatment. The inter-reliability of the assessments was good with concordance of ratings of 90% and weighted kappa of 0.8. RESULTS: Rates of full response to individual mood stabilizers were: lithium 30%, carbamazepine 0%, valproate 13%, lamotrigine 11%, and olanzapine 25%. Lithium responders were more likely to be bipolar II, and had a typically episodic course of illness with earlier onset in comparison with non-responders. Responders to valproate had higher rates of psychosis. LIMITATIONS: Data were obtained by chart reviews. CONCLUSIONS: Less than one-third of patients treated with lithium achieved remission; the effectiveness of other treatments in this naturalistic sample was even lower.