Question to the Department of Health and Social Care:

To ask His Majesty's Government what estimate they have made of the number of (1) adults, and (2) children, in England who have autism.

There is varied evidence on the ‘true prevalence’ of autism, which is the proportion of the population who would meet the criteria for a diagnosis if they were to be assessed, regardless of whether or not they have received a formal diagnosis.

Part II of the Adult Psychiatric Morbidity Survey, due to be released in Autumn 2025, will give us an indication of autism prevalence. We are also exploring options through the National Institute for Health and Care Research to improve our current understanding of autism prevalence.

In respect of numbers of people diagnosed as autistic, the NHS Network Contract Direct Enhanced Service dataset shows that, as of March 2025, 968,651 people, both children and adults, had an autism diagnosis recorded in their general practice (GP) records, based on 98.21% of the GP-registered population.

Evidence shows that there is variation in rates of autism diagnosis by age. Some information on diagnosis rates by age group can be taken from the Health and Care of People with Learning Disabilities, Experimental Statistics 2023 to 2024, published by NHS England, and based on 54.7% of registered patients. This data shows that 3.41% of zero to 17-year-olds have an autism diagnosis, compared to 0.79% in adults aged 18 years old and over. Evidence suggests that diagnosis rates remain below the levels indicated by evidence on prevalence in some cohorts, such as older people, but are higher than the most recent prevalence estimates in other cohorts, such as younger people.