Cost-Effectiveness of Financial Incentives to Promote Adherence to Depot Antipsychotic Medication: Economic Evaluation of a Cluster-Randomised Controlled Trial

Background Offering a modest financial incentive to people with psychosis can promote adherence to depot antipsychotic medication, but the cost-effectiveness of this approach has not been examined. Methods Economic evaluation within a pragmatic cluster-randomised controlled trial. 141 patients under the care of 73 teams (clusters) were randomised to intervention or control; 138 patients with diagnoses of schizophrenia, schizo-affective disorder or bipolar disorder participated. Intervention participants received 15 pound per depot injection over 12 months, additional to usual acute, mental and community primary health services. The control group received usual health services. Main outcome measures: incremental cost per 20% increase in adherence to depot antipsychotic medication; incremental cost of 'good' adherence (defined as taking at least 95% of the prescribed number of depot medications over the intervention period). Findings Economic and outcome data for baseline and 12-month follow-up were available for 117 participants. The adjusted difference in adherence between groups was 12.2% (73.4% control vs. 85.6% intervention); the adjusted costs difference was 598 pound (95% CI -4 pound 533, 5 pound 730). The extra cost per patient to increase adherence to depot medications by 20% was 982 pound (95% CI -8 pound 020, 14 pound 000). The extra cost per patient of achieving 'good' adherence was 2 pound 950 (CI -19 pound 400, 27 pound 800). Probability of cost-effectiveness exceeded 97.5% at willingness-to-pay values of 14 pound 000 for a 20% increase in adherence and 27 pound 800 for good adherence. Interpretation Offering a modest financial incentive to people with psychosis is cost-effective in promoting adherence to depot antipsychotic medication. Direct healthcare costs (including costs of the financial incentive) are unlikely to be increased by this intervention.