Autistic people more sensitive to pain than others - Israeli study

People with autism spectrum disorder supposedly are “indifferent to pain,” but a new Tel Aviv University (TAU) study has found that they experience pain at a higher intensity than the general population and are less adaptable to the sensation. The researchers expressed the hope that the findings of their study will lead to more appropriate treatment on the part of medical staff, caregivers and parents toward people with autism, who do not always express the experience of pain in the usual way. 

The study, entitled “Indifference or hypersensitivity? Solving the riddle of the pain profile in individuals with autism,” has just been published in the journal Pain. It was led by Dr. Tami Bar-Shalita at TAU’s Sackler Faculty of Medicine in collaboration with Dr. Yelena Granovsky of the Technion and the Rambam Healthcare Campus in Haifa and Prof. Irit Weissman-Fogel and Prof. Eynat Gal of the University of Haifa. The study constituted a framework for the theses of doctoral students Tzeela Hofmann and Mary Klingel-Levy,

About 10% of the general population suffer from sensory modulation dysfunction, which means sensory hypersensitivity at a level that compromises normal daily functioning and quality of life, said. Bar-Shalita. These people have difficulty, for example, ignoring or adapting to buzzing or flickering of fluorescent lights, humming of air conditioners or fans, or the crunching of popcorn by someone sitting next to them in the cinema.”

Exploring pain perception on the autism spectrum

In previous studies in the lab, they found that these people suffer from pain more than those without sensory modulation dysfunction. Since it is known that sensory modulation dysfunction occurs in people with autism at a rate of 70% to 90%, it constitutes a criterion for diagnosing autism and is associated with its severity. “We were interested in exploring pain perception in autism, so we asked: Do people with autism hurt more than the general population? This question had hardly been studied in the lab before we got started,” Bar-Shalita continued. 

According to the researchers, for many years the prevalent opinion was that people with autism hurt less or that they were indifferent to pain. “Actually, indifference to pain is one of the characteristics presented in the current diagnostic criteria of autism. The proof of this was supposedly their tendency to inflict pain on themselves by self-harm,” she added. “But this assumption is not necessarily true. We know that self-harm could stem from attempts to suppress pain, and it could be that they hurt themselves so as to activate unconsciously a physical mechanism of ‘pain inhibits pain.’ “ 

This study is a lab pain study approved by the ethics committee of the academic institutions and Rambam and included 52 adults with high-functioning autism (HFA) and normal intelligence. This created the largest reported sample in the world in studies on pain among people with autism. 

The team made use of psychophysical tests to evaluate pain that are commonly used for pain study. These methods examined the link between stimulus and response, while the researcher, using a computer, controlled the duration and intensity of stimulus. The examinee was asked to rank the intensity of the pain he felt on a scale of 0 to 100. The findings have proven beyond doubt that people with autism hurt more, and their pain suppression mechanism is less effective. 

The researchers explained that “we conducted a variety of measurements aimed, among other things, at examining whether the hypersensitivity to pain derives from a sensitized nervous system or from suppression of mechanisms that are supposed to enable adjustment and – over time – reduce the response to the stimulus. We found that in the case of people with autism, it is a combination of the two – an increase of the pain signal along with a less effective pain inhibition mechanism.”

“Our study constituted a comprehensive, in-depth study of the intensity of pain experienced by people with autism. The prevalent belief that they are supposedly indifferent to pain led medical and other professional staff to treat them accordingly,” Bar-Shalita concluded. “The results indicate that in most cases, sensitivity to pain in people with autism is actually higher than that of most of the population, while at the same time, they are unsuccessful at effectively suppressing painful stimuli. We hope our findings will benefit the professionals and practitioners handling this population and contribute to the advancement of personalized treatment.”