Drugs That Reduce Physical Pain Are Also Shown To Reduce Empathy For The Pain Of Others

The idea that some individuals are more affected than some by their environmental exposures and developmental experiences is part of an evolving theory known as differential susceptibility.

A study published this June led by Geoffrey R. O. Durso of The Ohio State University Department of Psychology aimed to identify any behavioral trends due to use of acetaminophen among individuals’ reactivity to both negative and positive stimuli. 

Used to relieve pain and fever, acetaminophen – known as paracetamol in the United Kingdom – is present in at least 600 medicines in America, including Tylenol.

Researchers carried out a three-pronged investigation:

Session 1

Involving 80 participants, half received a liquid containing 1,000 milligrams of acetaminophen, while the control group drank a placebo solution containing no acetaminophen. An hour later, each participant was given a series of short scenarios to read. The stories included characters who experienced some sort of traumatic physical or emotional pain – like a serious stab wound or the death a loved one. Then these character experiences were rated by participants.

Surprisingly, the team found that the individuals who had consumed acetaminophen rated the pain of the characters in the story as less severe.

Session 2

Involving 114 participants, half were given acetaminophen and the other half, placebo. Participants were subjected to short, loud blasts of white noise, then asked to rate the unpleasantness of the noise and how unpleasant they thought the noise would be for an anonymous participant.

Those who had taken the drug rated the noise as less unpleasant, and they also believed it would be less unpleasant for an anonymous participant.

Session 3

In the final part of the study, participants were allowed to mingle and chat before being removed from the social setting to one of isolation to sit alone and watch – but not participate in – an online “game.”

Participants were told that three of the people they had just met were playing. During the game, two of the participants excluded the third (although the participants were not really involved).

The individuals who were watching the game were asked to rate the emotional pain and hurt of the participant who was excluded.

“[…] those who took acetaminophen showed a reduction in empathy. They weren’t as concerned about the rejected person’s hurt feelings.” added senior author Baldwin Way.

At this stage, it is not clear why this reduction in empathy occurs. However, previous studies involving brain scans might give us a clue.

Researchers found that when an individual feels pain, and when they imagine pain in someone else, it causes a response in similar parts of the brain.

In other words, the regions of the brain involved in experiencing pain are also involved in imagining the pain of others.

Theoretically, if the same brain areas are used to both experience and imagine pain, a drug reducing real pain might also reduce imagined pain.

If the results are replicated, they would be highly relevant to the real world. After all, it would mean that one quarter of the population would be regularly taking a drug that reduces empathy.

“We don’t know why acetaminophen is having these effects, but it is concerning.” said senior author Baldwin Way

Because the research was carried out on a relatively small group, larger studies will be necessary to draw solid conclusions.