Diagnosis of common health conditions among autistic adults in the UK: evidence from a matched cohort study

Background: Autistic people are disproportionately likely to experience premature mortality and most mental and physical health conditions. We measured the incidence of diagnosed conditions accounting for the most disability-adjusted life years in the UK population according to the Global Burden of Disease study (anxiety, depression, self-harm, harmful alcohol use, substance use, migraine, neck or back pain, and gynaecological conditions). Methods: Participants were aged 18 years or above and had an autism diagnosis recorded in the IQVIA Medical Research Database between 01/01/2000 and 16/01/2019. We included 15,675 autistic adults without intellectual disability, 6437 autistic adults with intellectual disability, and a comparison group matched (1:10) by age, sex, and primary care practice. We estimated crude incidences and incidence rate ratios (IRRs) adjusted for age and sex. Findings: Autistic adults without intellectual disability experienced a higher incidence (IRR, 95% CI) of self-harm (2.07, 1.79–2.40), anxiety (1.91, 1.76–2.06), depressive disorders (1.79, 1.67–1.92), and substance use (1.24, 1.02–1.51) relative to comparison participants. Incidences of harmful alcohol use (1.01, 0.85–1.18), migraine (0.99, 0.84–1.17), and gynaecological conditions (1.19, 0.95–1.49) did not differ. Neck or back pain incidence was lower (0.88, 0.82–0.95). Autistic adults with intellectual disability experienced a higher incidence of self-harm (2.08, 1.69–2.56). Incidences of anxiety (1.14, 1.00–1.30), gynaecological conditions (1.22, 0.93–1.62), and substance use (1.08, 0.80–1.47) did not differ, and lower incidences were found for depressive disorders (0.73, 0.64–0.83), harmful alcohol use (0.65, 0.50–0.84), migraine (0.55, 0.42–0.74), and neck or back pain (0.49, 0.44–0.55). Interpretation: Although our findings cannot be directly compared to previous prevalence studies, they contrast with the higher frequency of mental and physical health conditions in autistic adults reported in studies that directly assessed and/or surveyed autistic people about co-occurring conditions. The present findings may suggest under-diagnosis of common conditions in autistic people, particularly those with intellectual disability. Improved detection should be a clinical and policy priority to reduce health inequalities. Funding: Dunhill Medical Trust, Economic and Social Research Council, National Institute of Health and Care Research.