Health-care utilisation and associated economic burden in major depressive disorder and treatment-resistant depression in a longitudinal population-based cohort study of 110.000 patients

Major depressive disorder (MDD), and particularly treatment-resistant depression (TRD), lead to high levels of health-care use and disease burden. The aim of this study was to evaluate and compare the health-care resource utilisation and associated costs in these patient groups. It was a population-wide, retrospective analysis of NHS health-care electronic records in northwest London using the Discover-NOW platform, one of the largest interlinked datasets in Europe hosted by Imperial College Health Partners, which contains coded emergency and routine, primary and secondary, physical and mental health data, covering a population of more than 2.5 million. Eligible patients were adults with a diagnosis of MDD who had been prescribed at least one antidepressant between 2015 and 2020. A total of 110,406 patients were included, 101,333 [92%] with MDD and 9073 [8%] with TRD. Mean duration of depression was 52.8 (SD 41.7) months for MDD and 70.8 (SD 37.8) months for TRD (p < 0.0001). Patients with TRD had significantly higher risks of both psychiatric and somatic comorbidities such as anxiety, asthma, and alcohol misuse (all p < 0.0001). They also demonstrated increased primary care and emergency attendance rates, more frequent and longer hospitalizations, and on average 1.5 times greater total healthcare costs compared to MDD patients. Primary care visits represented the largest proportion overall (TRD mean 162 [SD 96] vs. MDD 108 [90] visits per patient, p < 0.0001; cost per patient £17,348 [SD £33,040] vs. £12,011 [£25,588], p < 0.0001) during the study period. In secondary care, accident and emergency visits accounted for the highest use (TRD mean 5.5 [10.6] vs. MDD 3.54 [SD 6.0] visits per patient, p < 0.0001) while non-elective hospitalisations incurred the highest costs (mean £2518 [£8064] vs. £1909 [SD £6807], p < 0.0001). Demand increased with the duration of depression and the number of lines of treatment. The study highlights the substantial clinical and economic burden associated with MDD and especially TRD across different care settings.