In the UK GP Patient Survey, from 2018-25, proportion of self-reported autism in adults aged 25 & over increased from 0.6% to 2.0%? vs from 3.4% to 8.9% in 16-24 year-olds? link.springer.com/article/10.1... note: the survey does not ask "whether the participant has received a professional diagnosis"
link.springer.com
Trends in Self-Reported Autism Among Adults in England: Analysis of a Repeated Cross-Sectional Patient Survey Series of 5,999,433 Adults - Journal of Autism and Developmental Disorders
Purpose Whether autism is increasing is a subject of growing interest to researchers, health and social care professionals, policymakers, and the general public. We examined trends over time in the pr...
