Prospective Study to Determine the Prevalence of Signs of Central Sensitization in Adults With ASD Without Intellectual Developmental Disorders

Autism is a neurodevelopmental disorder (NDD) characterized by two key features: persistent deficits in communication and social interaction, and restricted, repetitive patterns of behavior, interests, and activities. Ninety-five percent of children aged 3 to 6 with autism spectrum disorder (ASD) have sensory peculiarities. In adulthood, this figure remains at 90%. This atypical sensory processing has been part of the DSM diagnostic criteria since 2013.

Each sense can be affected by hypo- or hypersensitivity. In the continuum of this particular sensory processing, pain, which is defined as an unpleasant sensory and emotional experience, can be very present but also difficult to detect and manage. It is now established that there are other characteristics that impact pain in ASD: information processing time may be longer, referred to as "latency time," but there are also difficulties in representing the body schema and difficulties in identifying and/or interpreting perceptions. Expression may be atypical, and there may be an apparent lack of reaction to pain due to a lack of flexibility.

All of these characteristics themselves vary over time (with age, the menstrual cycle, lack of sleep, fatigue, etc.), to the point that even pain specialists in pain clinics may not recognize them.

It is therefore essential to carry out appropriate, individualized assessments.

The scientific literature refers to the high frequency of painful events in ASD. For example, the prevalence of gastrointestinal disorders with their associated abdominal pain is significantly higher. Recent research has revealed that 82.4% of children and adolescents with ASD have at least one gastrointestinal symptom. Researchers have found that children with ASD are almost eight times more likely to have one or more chronic gastrointestinal symptoms than typically developing children. There are also more common comorbidities that facilitate or maintain chronic pain: Ehler Danlos syndrome and hypermobility spectrum disorders, IBD, ADHD, post-traumatic stress disorder, depression, migraines and tension headaches, anxiety disorders, epilepsy, small fiber pathologies, nutritional deficiencies, musculoskeletal disorders, etc.

Mutations in certain genes involved in ASD (such as SCN9A, SHANK3, and CNTNAP2) lead to impaired neuronal function, producing different responses to pain, as demonstrated in both mouse and human models. The links between ASD and chronic pain are therefore complex. Sometimes it is the unusual characteristics of the pain that could lead to a diagnosis of ASD.

The concept of central sensitization (CS), which underlies the type of pain known as "nociplastic," helps explain the state of pain hypersensitivity and pathologies such as fibromyalgia and irritable bowel syndrome. In 2022, Grant et al. found that 21% of adults with ASD surveyed in the cohort reported having a diagnosis of central sensitization syndrome (CSS), but 60% scored at or above the cut-off. This suggests that CS symptoms such as pain and fatigue are very common in people with autism, and perhaps more prevalent than in the general population. For example, three-quarters of women diagnosed with ASD and/or ADHD in childhood report chronic pain in adulthood.

The issue is the disability associated with this chronic pain and the impairment of quality of life.