Estimating health utilities and quality adjusted life years in seasonal affective disorder research.

BACKGROUND Seasonal affective disorder (SAD) episodes will recur annually without effective intervention. Effectiveness of such interventions is traditionally measured with depression-specific tools (e.g., Beck Depression Inventory 2nd Edition; BDI-II). In a climate of potentially scarce resources, generic outcomes, such as Quality Adjusted Life Years (QALYs), are recommended for cost-effectiveness research. For treatments to be deemed cost-effective, they must show effectiveness relative to each other and relative to interventions across other disorders. To date, QALYs have not been used to determine effectiveness of SAD treatments. Given the recurrent nature of SAD, QALYs, which weight quality of life with time, are an ideal SAD treatment outcome. METHOD A method to assess QALYs for SAD was developed using pilot clinical trial data. The method estimated health utilities, a measure of quality of life for a QALY, by anchoring pilot BDI-II data from the SAD clinical trial with previously derived health utilities for nonseasonal depression. RESULTS Relative to no treatment, median QALYs gained ranged from 0.11-0.18 over 1 year, depending on the intervention assessed. DISCUSSION Any treatment for SAD must compete with spontaneous spring remission, as illness severity attenuates in the spring. LIMITATIONS Health utilities were estimated from the depression literature, and potential side effects from SAD treatments were not included in the estimates. The clinical trial time horizon was limited to 1-year. CONCLUSIONS The proposed method offers researchers a tool to transform SAD efficacy data into a generic outcome for use in cost-effectiveness analysis of SAD treatments.