CLINICAL AND ECONOMIC BURDEN OF MAJOR AND TREATMENT- RESISTANT DEPRESSION IN A POPULATION-BASED STUDY COHORT OF 110.000 PATIENTS

Abstract Background Major depressive disorder (MDD) is a leading cause of global disability. Despite availability of effective therapies, many patients with MDD develop treatment-resistant depression (TRD). Aims To evaluate and compare treatment outcomes, comorbidities and healthcare resource usage and costs in patients with major depressive disorder (MDD) and treatment-resistant depression (TRD). Methods This was a population-based, retrospective analysis of linked primary and secondary care NHS data in the northwest London Discover-NOW dataset. This is the access platform for the longitudinal Whole Systems Integrated Care (WSIC) database, which is hosted by Imperial College Health Partners and contains linked coded primary, acute, mental health, community health, and social care records fed by over 400 provider organisations and covering more than 2.5 million patients. Eligible patients were adults who were registered with a General Practitioner in the area, had diagnostic codes for depression and had been prescribed at least one antidepressant between 2015 and 2020. Results A total of 110,406 patients were eligible for inclusion (101,333 [92%] with MDD and 9,073 [8%] with TRD). Mean duration of depression was 52.8 (SD 41.7) months and 70.8 (SD 37.8), respectively. Remission was recorded in 42,348 (42%) patients with MDD and 1,188 (13%) with TRD (p<0.0001) while relapse was seen in 20,970 (21%) and 4,923 (54%), respectively (p<0.0001) during the study period. Patients with TRD had significantly higher risks of suicidal behaviour and comorbidities such as anxiety, asthma, and alcohol/substance misuse (all p<0.0001). Mean times from diagnosis to first contact with mental health services were 38.9 [SD 33.6] months for MDD and 41.5 [SD 32.0] months for TRD (p<0.0001). Individuals with TRD had considerably higher primary care and emergency attendance rates, more inpatient hospitalizations, longer hospital stays, and greater total healthcare costs than MDD patients. Demand increased with the duration of depression and the number of lines of treatment. Primary care usage was greatest overall (TRD mean 162 [SD 96] vs. MDD 108 [SD 90] visits per patient, p<0.0001; cost per patient £17,348 [SD £33,040] vs. £12,011 [£25,588], p<0.0001). 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 £ 2,518 [£8,064] vs. £1,909 [SD £6,807], p<0.0001). Conclusions The study highlights the substantial individual patient and economic burden associated with MDD and particularly TRD in both primary and secondary care settings. Findings suggest that evidence- based treatment optimisation, timely access to newer therapies and the development of stratified care pathways and specialist services could improve patients’ outcomes.