There probably is not a more overused and less useful term in the field of autism than "high-" or "low-functioning." The words are used by parents, professionals, media, everyone. Yet they carry no meaning and interfere with getting supports. Initially, the term "high-functioning autism" was meant to indicate that the autistic person has average or above-average cognitive functioning, i.e. there is no intellectual delay. Conversely, someone "low-functioning" has an intellectual delay. Through incorrect clinical and everyday use, these words are now commonly employed to imply an actual level of functioning and even a potential developmental trajectory. You can often hear professionals say things like, “High-functioning kids like yours tend to do very well with intervention.” A recent study (Alvares et al., 2020) showed that "high-functioning" autistic individuals do not function well in real life. Their ability to function socially, to self-regulate, to hold a job, and to manage everyday life was not well-predicted by their IQ scores. The researchers argued that the term is harmful as it sets up incorrect expectations for functioning. They suggested not using it. The autistic community and many professionals have been saying this for a long time. A person with average to above-average intelligence has a strength that will help in learning. But that same person could have other challenges. For a child, those challenges could make it hard to have friends, understand books, go on outings, play with classmates, do well in school, follow school rules, and get along with family. Adults could have trouble managing money, taking care of a household, using public transportation, organizing their time, having a close relationship, holding a job, or studying in college. Co-morbid medical or mental health issues, sensory issues, executive functioning challenges, fine and gross motor skills, self-regulation, attention, social skills, and problem-solving ability all affect how a person functions day-to-day. An IQ score is not a reliable predictor of the type and the amount of support an autistic person needs. A person on the spectrum can have exceptional abilities in some areas and significant challenges in other areas, while their skills in yet other areas might be average. Levels of functioning in specific domains are different from person to person and create unique autistic profiles. Thinking about areas or domains of functioning leads to more accurate picture of person's abilities than using black-and-white descriptors such as “high-“ and “low-functioning.” It is very upsetting and discouraging for an autistic person who experiences daily challenges to be dismissed as not needing support because of the “high-functioning” label. Conversely, an autistic individual with a cognitive delay, who is labeled as "low-functioning," can face low expectations, although that person might show average and even above-average functioning in some areas. We need to use more precise language and nuanced thinking to understand complex and unique autistic profiles. It is crucial for the ability of autistic individuals to use their strengths and receive the supports they need.
Reference: Autism. 2020 Jan;24(1):221-232. The misnomer of 'high functioning autism': Intelligence is an imprecise predictor of functional abilities at diagnosis. Alvares GA, Bebbington K, Cleary D, Evans K, Glasson EJ, Maybery MT, Pillar S, Uljarević M, Varcin K, Wray J, Whitehouse AJ.