Developing a consensus research definition for profound autism using a modified Delphi method

The diagnostic term, autism spectrum disorder, encompasses the full range of impairments associated with the autism spectrum, a significant change from earlier DSM definitions that identified various subtypes of autism. However, the majority of autism-related research and cultural representations in recent years has focused on autistic individuals with strong language and cognitive abilities. In 2021, the administrative term Profound Autism (PA) was proposed by a Lancet Commission to draw attention to autistic people whose impairments require lifelong, round-the-clock care. The initial definition of PA included a minimum age and requiring 24/7 access to an adult to ensure safety, and suggested considering IQ, and verbal ability when defining this group. However, researchers have subsequently utilized widely varying criteria in studies of this group, producing results that are difficult to compare and limit the potential for the identification of this group to advance knowledge about their strengths and needs.

To address the need for studies that use comparable samples and increase clarity in communication and interpretation of results, we carried out a systematic, multi-stage Delphi consensus study with over 70 participants who identified as researchers, caregivers, autistic individuals, and clinicians, to measure consensus on components of a research definition of PA. A series of questions was developed for the primary domains of interest.

After two rounds of review and voting, 76% of the respondents agreed on a research definition of PA of: adaptive functioning well below age level, requiring adult supervision to ensure physical and mental health, safety and well-being, being at least 8 years old, diagnosed with ASD, and having severely impaired cognitive abilities (reflected by IQ score below 50) and/or not verbally communicating other than single words or fixed phrases used predominantly to have their basic needs met.

Variations in access to measurement tools, as well as access to services across the world, limit the utility of this definition outside research practices, and a response rate of 58% yielded a final round sample size of 78 that may underrepresent portions of the stakeholder community and was overwhelmingly composed of respondents from the United States.

Based on these findings, a new working research definition of profound autism is proposed. Adoption of this definition could improve comparability across research studies, enhance the impact and generalizability of results, and better target interventions and supports for this high-needs group.