Acetaminophen is a common painkiller. Researchers from the Ohio State University found that when participants who took acetaminophen learned about another person's grievances, they thought the person is experiencing less suffering. This suggested lowered empathy when compared with participants who didn't take the painkiller.

The study involved two experiments. In the first one, researchers enrolled 80 college students. Randomly, half drank a liquid formula with 1,000 mg of acetaminophen while half took a placebo at the beginning of the study.

After an hour, the participants were asked to read eight scenarios wherein a character experienced pain. The scenarios varied from a deep knife cut to the loss of a loved one.

From one to five, with five being the highest, the participants rated the levels of pain the characters in the scenario experienced. The students also rated how much the characters felt wounded, pained and hurt. The acetaminophen participants' ratings were "less severe" compared to the ones on placebo.

"These findings suggest other people's pain doesn't seem as big of a deal to you when you've taken acetaminophen. Acetaminophen can reduce empathy as well as serve as a painkiller," said study co-author Dominik Mischkowski from the National Institutes of Health and a former doctoral student at the Ohio State University.

The second experiment enrolled 114 college students who either took acetaminophen or a placebo formula. For the first part, the students received two-second white noise blasts four times, each ranging between 75 to 105 decibels.

They were asked to rate the blasts on a scale of 1 to 10, with 10 being the most unpleasant. Then they were asked to rate how much pain another person would endure because of the blasts. The results were the same with the first experiment.

The second part was a social experiment wherein one person is excluded from an activity. Participants were asked to rate the level of hurt and pain the booted individual must have felt. The social experiment produced the same results.

"Still, those who took acetaminophen showed a reduction in empathy. They weren't as concerned about the rejected person's hurt feelings," said Psychology Assistant Professor Baldwin Way, who conducted the experiments with Mischkowski.

According to the Consumer Healthcare Products Association, acetaminophen is the most common ingredient in drugs found in the United States such as Tylenol.

In fact, acetaminophen is so common that 23 percent (roughly 52 million) of adults in the United States pop a medication containing this ingredient.

The findings were published in the Social Cognitive and Affective Neuroscience journal on May 5.

Photo: Michelle Tribe | Flickr