OBJECTIVES: Long-term burden and trend of health resource utilization (HRU) of treatment-resistant depression (TRD) beyond 24 months are rarely reported, we therefore aimed to assess the temporal trend of all-cause HRU and compare the medical cost between patients with and without TRD.

METHODS: Using the local territory-wide electronic medical records, we retrospectively followed up 8,223 incident patients diagnosed in 2014 from their first diagnosis to death or December 2019 for TRD identification (i.e. having ≥2 antidepressant regimens for a defined duration and a third regimen to confirm previous failures). We matched the TRD patients 1:4 to the non-TRD on propensity scores estimated by age, sex and medical history. Costs were aggregated from attendance and admission records in 14 service types multiplied by unit costs valued at 2019 Hong Kong Dollars. We examined the annual and cumulative trend of HRU and cost over six years using relative changes and cumulative annual growth rates (CAGR), then performed negative binomial regression to compare mean HRU and cost by year, by service type and at an overall level.

RESULTS: Both TRD (18.1%) and non-TRD patients had decreasing HRU across six years, with strongest relative decline (28-55%) within the first two years then slow decline in subsequent years. Outpatient setting contributed ≥85% of service utilization but hospitalization accounted for ≥72% of costs owing to prolonged stay and high unit costs. Cumulative cost rose steadily with a CAGR of 23.4% (TRD: 27.5%; non-TRD: 21.9%). TRD was associated with greater HRU across settings and years (p<0.001), and imposed 54% higher overall cost per patient year [$116,731 vs $75,666, adjusted odds ratio: 1.80 (95%CI: 1.63-2.00)]. Patients with TRD also used more psychiatric and non-psychiatric resources.

CONCLUSIONS: Our findings highlight the chronicity and immense burden associated with TRD, and urge for effective management beyond available care to relieve long-term economic burden.