There are many aspects of autism spectrum disorders that remain, for lack of a better word, mysterious. As someone who is on the autism spectrum himself, I can personally attest to such enigmatic realities as the double empathy problem, which describes how autistic and non-autistic people fundamentally differ in how they communicate. People on the autism spectrum sometimes have hard-to-explain physical disabilities in addition to communication issues, and statistics prove that men are more likely to develop autism than women.
"Once a sensation is painful, the intensity of these pains might be higher in autistic adults compared to their non-autistic peers," Moore explained.
And there is the autism-pain problem. As a child, I used to run and hide under the bed whenever I heard a train passing by because the stimuli made me feel uncomfortable. For other autistic people, the problem involves a tendency to be more agitated than usual by physical pain such as being given shots or dealing with routine injuries.
Earlier this month, a study by Israeli researchers in the scientific journal PAIN illuminated this under-explained aspect of autism: Why autistic people seem to be more sensitive to pain, whether it's hypersensitivity to lights and sounds or an unusually acute response to literal physical pain.
After conducting an experiment with 52 adults who were either high-functioning autistic (HFA) or neurotypical, the largest reported sample for a study on pain in autism in the world, the scientists concluded that there are two factors at play in autism: "an increase of the pain signal along with a less effective pain inhibition mechanism."
Yet the researchers also added that much more work will need to be done to understand the exact neurological mechanisms that cause autistic people to experience pain more acutely. Indeed, more broadly, scientists need to understand why the experience of pain is so inherently subjective from person to person.
"People certainly feel pain in different ways and to different degrees," Michelle D. Failla, PhD, Research Assistant Professor at The Ohio State University College of Nursing, told Salon by email. (Failla was not involved in the Israeli study.) "There is variation in how much people feel and express pain that can be related to general individual variation across people, but also different life experiences, medical conditions, gender, race, and many other factors. People also can experience pain differently at different times in their lives – so it can change even by the situation for each person."
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"We also see differences in pain responses in some other neurodivergent populations."
When it comes to studying the specific problem of autism and pain, the tricky part is ascertaining exactly how much of a role the autism disorder itself plays in the pain sensation. Dr David Moore, who studies pain psychology at Liverpool John Moores University (and was likewise not involved in the Israeli study), wrote to Salon that he and his colleagues have compared pain thresholds between autistic and non-autistic people. While they have not found evidence of differences when it comes to literal pain thresholds — "the intensity required for a person to report that a sensation is painful" — this is not the case when it comes to how intensely people perceive their pain once it has been registered.
"Once a sensation is painful the intensity of these pains might be higher in autistic adults compared to their non-autistic peers," Moore explained. "This might suggest that once a pain is perceived that suffering is more acute for autistic people." He also noted that autistic people who are more likely to experience conditions like joint hypermobility and gastrointestinal problems, which exacerbate their discomfort.
"We also have reason to suspect that autistic people are more likely to need management within tertiary chronic pain clinics suggesting the greatest levels of care are more likely to be required," Moore told Salon.
Autism is not alone among neurological and developmental conditions that seem to cause an increased subjective response to pain. Nouchine Hadjikhani, a professor in the Department of Psychiatry and Neurochemistry at the University of Gothenburg, told Salon that conditions like fibromyalgia have been linked to heightened pain sensitivity, especially in women. Overall, Hadjikhani lamented the insufficient amount of research into how pain is felt by different demographic groups. This research could be very useful.
In terms of why autistic people seem to feel pain more acutely, Hadjikhani says that "it that has not been proven and shown directly, but it really seems like this is because the autistic brain has an imbalance between excitation and inhibition, it's more susceptible to process signals with more intensity compared with the brains of typical people."
Failla concluded, based on her research, that while autistic people may experience pain more strongly in certain ways "reflected in different brain responses to pain," there is also evidence of the opposite.
"We see that other autistic people may experience pain less strongly at some times," Failla wrote. "We also see differences in pain responses in some other neurodivergent populations, but there isn't enough research to definitively say how much this is linked to neurodivergence yet. We continue to work on this in our research."