Factors associated with antipsychotic adherence in adults with schizophrenia - A real-world evaluation

Adherence to antipsychotics is a critical, modifiable determinant of clinical and functional outcomes in schizophrenia care. We sought to identify determinants of antipsychotic medication adherence among individuals with schizophrenia.

We conducted a cross-sectional analysis of linked administrative health data from a population-based sample of community-dwelling adults (age 18-65) diagnosed with schizophrenia in Alberta, Canada. Antipsychotic adherence was estimated using the proportion of days covered across the five-year period from April 1, 2016 - March 31, 2021. Continuous adherence was dichotomized using a threshold of 0.80 medication coverage over the lookback period. Multivariable logistic regression was used to model nonadherence as a function of 35 variables covering sociodemographic characteristics, markers of mental and physical health, medication characteristics, and health service utilization.

We identified 24,309 individuals with schizophrenia in Alberta. Overall adherence (as measured by the average proportion of days covered) was 0.60 (SD 0.35) over the lookback period. 14,253 (58.6%) of individuals were classified as nonadherent. Most of the factors examined in our model were associated with adherence. Continuity of care, concomitant psychiatric medication use, and long-acting injectable antipsychotic formulations were associated with better adherence. Conversely, a recent diagnosis of schizophrenia, psychiatric comorbidities, and homelessness were associated with lower adherence.

Despite the criticality of adherence for antipsychotic effectiveness, more than half of Albertans with schizophrenia demonstrated adherence lower than the threshold deemed to be optimal treatment. This work has identified many potentially modifiable factors that will be important targets for improving care and adherence-related outcomes in this population.