Background: Non-adherence to medications is common in bipolar disorder but its prevalence estimations have varied significantly. In addition, non-adherence is known to increase the risk of poor clinical outcomes. Therefore, we studied how common primary non-adherence for mood stabilizers and antipsychotics is in Finland and which factors are associated with it.
Methods: Nationwide sample of persons diagnosed with bipolar disorder during 1987-2018 were identified from registers. Dispensings of their electronic prescriptions during 2015-2018 were followed up to define rates of primary non-adherence. Primary non-adherence was defined as having at least one non-dispensed mood stabilizer or antipsychotic prescription during 2015-2018. In a broader definition, non-adherence was defined as having ≥20 % of mood stabilizer and/or antipsychotic prescriptions non-dispensed. Adjusted logistic regression was used to assess risk factors for non-adherence.
Results: The study cohort included 33,131 persons and 59.1 % had at least one non-dispensed mood stabilizer or antipsychotic prescription. 31.0 % of the cohort was non-adherent to ≥20 % of their mood stabilizer and/or antipsychotic prescriptions. Lithium and clozapine had the lowest proportions of non-dispensed prescriptions. Especially young age, recent bipolar disorder diagnosis, multiple hospitalizations due to bipolar disorder, and use of benzodiazepines or antidepressants were associated with an increased risk of non-adherence.
Limitations: This study was based on register data, and patient-reported reasons for medication non-adherence could not be included.
Conclusions: The majority of patients with bipolar disorder do not use their medications as prescribed. Patient-specific risk for non-adherence should be assessed and those at high risk for non-adherence should be followed closely.
Keywords: Antipsychotic agents; Bipolar disorder; Cohort studies; Medication adherence; Mood stabilizers.
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