OBJECTIVES: Non-adherence to psychotropic medications is a main cause for antipsychotic treatment failure. Among individuals living with schizophrenia or bipolar disorder, several reasons for non-adherence have been cited, including attitudes about medication and side-effects. Multiple studies have identified weight gain, obesity, or perceived weight status as associated with poor adherence.

METHODS: We used EHR data to identify individuals with at least one 60-day continuous use of antipsychotics between 2005 and 2019. Patients were identified from diagnoses as schizophrenic, bipolar, or psychiatric controls (neither a schizophrenia nor bipolar diagnosis). Using changes in weight over the first 90 days of antipsychotic use, we examined the association of weight gain with the proportion of days covered (PDC) with an antipsychotic and with the frequency of medication switching or stopping.

RESULTS: We identified 590 individuals with schizophrenia, 819 with bipolar disorder, and 642 psychiatric controls. In the first 90 days, the mean PDC ranged from 0.85 (psychiatric controls) to 0.89 (schizophrenia), and the percent with a PDC > .8 were 76.8% (schizophrenia), 77.1% (bipolar), and 70.7% (controls). Logistic regression models revealed that weight gain of 7% or more trended toward being significantly associated with greater adherence in the first 90 days (odds ratio = 1.29, 95% confidence interval [0.97, 1.71]; p=0.077). However, weight gain was significantly associated with an increased likelihood of a psychotropic medication switch in the first 180 days (odds ratio = 1.60, 95% confidence interval [1.17, 2.18]; p=0.003). An interaction between switching and cohort was not significant (p=0.79) indicating this result was consistent across cohorts.

CONCLUSIONS: Patients who were adherent the first 90 days tended to have more weight gain. Patents whose weight increased by 7% or more in the first 90 days were more likely to switch psychotropic medications during the first 180 days.