- Background: Subsets of psychiatric patients gain excess body weight while receiving mood-stabilizing agents such as lithium carbonate or valproate sodium. Patients who gain excess weight may discontinue therapy, with severe consequences. Among the newer anticonvulsant agents, topiramate is a candidate agent for bipolar disorder and is associated with weight loss when used as adjunctive treatment. Objective: This open-label, nonrandomized, chart-review study assessed changes in body weight and body mass index (BMI) in patients receiving topiramate, lithium, or valproate. Methods: Data were extracted from the medical charts of patients admitted in 1999 and 2000 to a state psychiatric hospital with either schizophrenia, schizoaffective disorder, bipolar disorder, or other psychiatric diagnoses who were prescribed valproate, lithium, or topiramate and were reviewed for changes in body weight and BMI. The use of concomitant psychotropic medicines was recorded (eg, antipsychotic agents, antidepressant agents, other mood stabilizers such as gabapentin or carbamazepine). Continuous variables were analyzed using a factorial analysis of variance and the Student t test. Contingency statistics were used to analyze categorical variables. Results: A total of 214 patients were included in the chart review (123 men, 91 women; mean age, 39.4 years). Significantly more women than men received topiramate (P = 0.004). Patients receiving either lithium or valproate gained a mean (SD) of 6.3 (9.0) kg and 6.4 (9.0) kg, respectively, whereas patients receiving topiramate lost a mean 1.2 (6.3) kg (F = 11.54, df = 2,198; P < 0.001). Lithium- or valproate-treated patients experienced an increase in BMI (mean, 2.1 [3.0] for both groups), whereas topiramate-treated patients experienced a reduction in BMI (mean, −0.5 [2.4]); this result was statistically significant (F = 11.40, df = 2,198; P < 0.001). Finally, lithium- or valproate-treated patients gained ⪢8% of their baseline body weight (8.2% [11.5%] for lithium-treated patients and 8.5% [11.9%] for valproate-treated patients), whereas topiramate-treated patients lost 0.7% (7.2%) of their body weight (F = 9.93, df = 2,198; P < 0.001). Conclusions: Controlled studies for the efficacy of topiramate therapy in various psychiatric conditions are awaited. These data indicate that patients receiving topiramate experience body weight loss and a reduction in BMI. This advantage of topiramate may promote long-term adherence to treatment among psychiatric patients and possibly decrease the medical risks associated with obesity.