Acetaminophen may impair the brain’s ability to detect errors, according to a study published on Feb. 17 by researchers from the University of Toronto. The study published in the journal Social Cognitive and Affective Neuroscience states that people are less reactive to uncertain situations after taking the popular painkiller.

The study is the first one to explore how this popular painkiller prevents the necessary brain response for error detection. This involved two groups of 30 participants who went through Go or No Go, a target-detection task.

These individuals had to hit the Go button each time the letter F was shown on a screen but were not allowed to hit it if the letter E was shown instead. They needed to move very quickly, capturing all the GOs, but must refrain from doing anything if they see a No Go.


A study shows acetaminophen could be hindering error-detection in the brain. Photo from Pixabay/Shivmirthyu

The researchers looked into brain waves called Error Related Negativity (ERN) and Error Related Positivity (Pe). If the participants made an error, an electroencephalogram (EEG) would show an increase in these waves.

One group received a placebo while another received acetaminophen. None of the participants or researchers knew which of these two were being handed out.

After administering 1,000 milligrammes of acetaminophen, one group exhibited a smaller Pe wave when making errors than those who did not get the drug. This showed that the painkiller prevents one’s conscious awareness of mistakes.

“It looks like acetaminophen makes it harder to recognize an error, which may have implications for cognitive control in daily life,” says researcher Dan Randles. “When you see a No Go, that requires cognitive control because you need to interrupt the process.”

Moreover, those who got an acetaminophen missed more of the Go stimuli. Still, the researchers admit that more studies are needed to verify the distraction stemming from the acetaminophen dose.

“An obvious question is if people aren’t detecting these errors, are they also making errors more often when taking acetaminophen?” adds Randles. “This is the first study to address this question, so we need more work and ideally with tasks more closely related to normal daily behaviour.”