A Reliable Effect of Alexithymia, but Not Autism, on Placebo Hypoalgesia

We understand pain through the sensory experience and our past experiences of how it felt before. This that creates an expectation of what it should feel like. This is perception inference. But, when factors like cognition or environment disrupt the interpretation of pain signals it can alter the experience and intensity.

Researchers thought that autistic people rely more on sensory input than expectations of how the pain ‘should’ feel. So, the autistic pain of a stubbed toe would not come with the worries of a previous stubbed toe. This research says that this is not correct, but it may be true for people with alexithymia.

Pain and our ability to spot emotions go together.

A difference and sometimes a struggle to spot emotions is called alexithymia. Alexithymia affects approximately 50% of the autistic population, but only about 5% of the majority population. Many autistic people have alexithymia, but previous research has often failed to distinguish the two.

This study aimed to explore whether alexithymia would predict the extent of pain reduction after receiving placebo treatment that they believe will relieve pain. A placebo effect is when medicine or treatment works when humans believe it works.

There were 109 participants (18-50 years old) who were categorised into groups based on their traits and diagnoses:

• Autistic and alexithymia
• Autistic without alexithymia
• Alexithymia without autism
• No autism and no alexithymia

Participants thought they were trialling a new TENS machine pain relief system.  They had their initial pain tolerances calibrated.  Pain was created through an electrode sending electrical pulses to the participants right inner wrist. They made sure to find a pain level they would not get used to over the trial. A TENS machine was then brought in and its use linked to seeing a red cross or a green cross.

On a pain trial they would have 100% pain stimulation when the TENS machine was off, and 60% pain stimulation when the TENS machine was on (providing some pain relief). But then the experiment changed for the placebo, they did 100% pain with the TENS machine either on or completely off (but the red and green crosses still displayed). This was to see if there was a change in perceived pain if participants thought a pain relief system was still working.

They found that higher alexithymic traits were linked to a greater initial placebo effect. Alexithymic individuals relied on seeing the green crosses to understand the pain experienced. There was little evidence of an association between autistic traits and placebo effect. Autistic pain is like neurotypical pain, it is alexithymic pain that is different.

Different ways of spotting your own emotions leads to different pain perception.  Because of the large overlap with alexithymia and autism, these alexithymic traits should be thought about for when designing pain relief treatments for the autistic community.

Summary by Holly and Clarissa