Severe Mental Illness Among Adults with Atopic Eczema or Psoriasis: Population-Based Matched Cohort Studies within UK Primary Care

Elizabeth I Adesanya,1 Alasdair D Henderson,1 Julian Matthewman,1 Ketaki Bhate,1 Joseph F Hayes,2 Amy Mulick,1 Rohini Mathur,1 Catherine Smith,3 Helena Carreira,1 Sujit D Rathod,4 Sinéad M Langan,1 Kathryn E Mansfield1 1Department of Non-Communicable Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK; 2Division of Psychiatry, University College London, London, UK; 3St John’s Institute of Dermatology, Guys and St Thomas’ Foundation Trust and King’s College London, London, UK; 4Department of Population Health, London School of Hygiene & Tropical Medicine, London, UKCorrespondence: Elizabeth I Adesanya, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK, Email elizabeth.adesanya@lshtm.ac.ukBackground: Existing research exploring associations between atopic eczema (AE) or psoriasis, and severe mental illness (SMI – ie, schizophrenia, bipolar disorder, other psychoses) is limited, with longitudinal evidence particularly scarce. Therefore, temporal directions of associations are unclear. We aimed to investigate associations between AE or psoriasis and incident SMI among adults.Methods: We conducted matched cohort studies using primary care electronic health records (January 1997 to January 2020) from the UK Clinical Practice Research Datalink GOLD. We identified two cohorts: 1) adults (≥ 18 years) with and without AE and 2) adults with and without psoriasis. We matched (on age, sex, general practice) adults with AE or psoriasis with up to five adults without. We used Cox regression, stratified by matched set, to estimate hazard ratios (HRs) comparing incident SMI among adults with and without AE or psoriasis.Results: We identified 1,023,232 adults with AE and 4,908,059 without, and 363,210 with psoriasis and 1,801,875 without. After adjusting for matching variables (age, sex, general practice) and potential confounders (deprivation, calendar period) both AE and psoriasis were associated with a