Objectives: Obsessive-compulsive disorder (OCD) is a chronic and debilitating psychiatric condition, with diagnosed patients typically experiencing moderate or severe symptoms. This study evaluated the cost-of-illness (CoI) of OCD in the UK, capturing the annual costs accrued to the National Health Service (NHS) and Personal Social Services (PSS), people with OCD, caregivers and society. Methods: The UK OCD population was estimated and stratified by age group (children, adults, elderly), symptom severity (mild, moderate, severe) and treatment received (including no treatment). Costs for each subpopulation were estimated through a prevalence-based approach. Cost inputs were sourced from national databases, while additional inputs were informed by literature searches or expert clinician opinion. Scenario analyses explored other factors including comorbid depression treatment and presenteeism. Results: The base-case analysis estimated a total annual CoI of 378,356,004 pound to the NHS, rising to 5,095,759,464 pound when a societal perspective was considered. The annual cost of care per person with OCD increased with severity (mild: 174; pound moderate: 365; pound severe: 902) pound due to increasing healthcare resource utilisation. The largest contributor to healthcare costs was cognitive behavioural therapy, while societal costs were driven by lost productivity through absenteeism. The base-case results likely underestimated the true economic burden of OCD; including comorbid depression led to a 132% increase in treatment costs, while presenteeism in people with OCD and lost productivity in caregivers amplified indirect costs. Conclusions: The economic burden of OCD in the UK is substantial and extends beyond direct treatment costs, highlighting a need for research into alternative treatments with greater efficacy.
