Assessment of factors associated with antipsychotic-induced weight gain: A nationwide cohort study.

Background: The incidence of antipsychotic-induced weight gain (AIWG) is difficult to predict in real-world practice because various factors influence it. This study aimed to explore background and medication-related factors associated with weight gain in patients newly prescribed with antipsychotic medication.

Methods: This nationwide, multicenter, prospective cohort study was conducted in Japan. The primary endpoint was the incidence of AIWG (≥7 % weight gain) over 12 months after initiation of antipsychotic treatment. Factors influencing AIWG incidence were assessed using Cox proportional hazards regression analysis stratified by facility characteristics.

Results: Of the 865 enrolled participants, 262 developed AIWG. Compared with aripiprazole, clozapine and olanzapine were related to a higher AIWG incidence (hazard ratio [HR] = 2.17, 95 % confidence interval [CI] = 1.05-4.51; HR = 2.01, 95 % CI = 1.36-2.96, respectively), whereas blonanserin was related to a lower AIWG incidence (HR = 0.49, 95 % CI = 0.24-0.98). Furthermore, co-administration of antidepressants and mood stabilizers increased the AIWG incidence (HR = 1.94, 95 % CI = 1.35-2.77; HR = 1.47, 95 % CI = 1.07-2.01, respectively). The impact of concomitant medications on AIWG incidence varied by the pharmacological characteristics of the newly initiated antipsychotic, in addition to the type and duration of concomitant medications.

Conclusions: The findings of this study suggest that the risk of AIWG incidence may be estimated by assessing the type of concomitant medication and its duration of use, type of newly initiated antipsychotic, and background factors prior to initiation of antipsychotic treatment.