Tylenol packages on shelf
Paracetamol, the active ingredient in Tylenol, can reduce empathy for others who are in painReuters

Taking paracetamol may make you less empathetic towards others, scientists say. This common painkiller and fever reducer − sold in the US under the name Tylenol − appears to make people less receptive to others' physical and social suffering.

The study, published the journal Social Cognitive And Affective Neuroscience, adds more substance to previous research regarding paracetamol, which suggested the drug could have a negative impact on emotions, going as far as dampening feelings of joy.

Here, the scientists from the Ohio State University show paracetamol could also affect the way we perceive the pains experienced by people around us.

"The findings suggest other people's pain doesn't seem as big of a deal to you when you've taken acetaminophen," said co-author Dominik Mischkowski, referring to paracetamol's other denomination.

Social ostracism and physical pain

The researchers conducted a range of double-blind placebo-controlled experiments that involved half of participants drinking a liquid containing 1,000mg of paracetamol, while the other half drank a placebo solution. They were then asked to rate on a scale of one to five perceived pain and personal distress of other participants.

In the first experiment, the subjects had to read stories in which characters experienced suffering on a physical or psychological level, receiving for example a knife wound or the news that their father had died. Those who had been given a placebo, rated the characters' levels of pain higher than the participants who had received paracetamol.

The second experiment consisted of watching a person getting ostracised by two others, and assessing the level of distress he or she must be feeling. There again, people on paracetamol showed less empathy and rated perceived social suffering as lower than other participants.

A last experiment had all the subjects receiving four two-second blasts of noise, which they rated on a scale of one (not unpleasant at all) to 10 (extremely unpleasant). They were also instructed to imagine how much pain it might have caused to another person.

Compared to those on the placebo, people on paracetamol rated the noise blasts as less unpleasant for themselves − but also for others.

In the brain

The findings can be illustrated by looking at people's brains. A 2004 study based on scans showed that when people experienced pain, the same parts of the brain were activated as when they empathised with other people who were suffering.

The implication is that dulling one's pain with paracetamol will thus dull the same part of the brain responsible for empathy. "In light of those results, it is understandable why using Tylenol to reduce your pain may also reduce your ability to feel other people's pain as well," the scientists say.

These results may have important consequences. Since empathy regulates social and antisocial behaviours, these drug-induced reductions in empathy indeed raise concerns about the broader social side effects of paracetamol.