Study: Acetaminophen dulls your pain -- but also your empathy

Story highlights

  • In one test, participants read sad scenarios and rated them
  • Researchers say they aren't sure why the drug is having this effect

(CNN)The side effects of popping a pain reliever containing acetaminophen are well-known: You may get stomach pains. You might feel nauseated.

Well, add another possible one to the list: You'll feel less inclined to empathize with your fellow man.
    A new study by researchers at Ohio State University found that acetaminophen -- the main ingredient in Tylenol and about 600 other medicines -- dulls you to the trials and tribulations of others.
    (By the way, these are the same researchers who earlier found that the medication can suck the joy out of life for you).
    "If you are having an argument with your spouse and you just took acetaminophen, this research suggests you might be less understanding of what you did to hurt your spouse's feelings," said study co-author Baldwin Way, an assistant professor of psychology and member of the Ohio State Wexner Medical Center's Institute for Behavioral Medicine Research.

    Reaching the conclusion

    For their study, which was published in the journal Social Cognitive and Affective Neuroscience, the researchers conducted several tests.
    In one, they rounded up 80 college students. They gave half of them a liquid with 1,000 mg of acetaminophen. The other half was given a liquid with no drug. Obviously, the students didn't know who was drinking what.
    After an hour for the drug to take effect, the participants read eight short stories with some really sad scenarios. For instance, one was about a person who suffered a knife wound that went to the bone. Another was about someone grappling with the death of his father.
    The students were asked to rate the pain of the person in the scenario.
    The placebo group (i.e. the ones who didn't take the acetaminophen) rated it highly. The acetaminophen group didn't think it was that big of a deal.
    In another study, the participants were given two-second blasts of white noise that ranged from 75 to 105 decibels. They were asked to rate how unpleasant it was for them and how unpleasant it would be if some other poor guy were subjected to the same.
    The acetaminophen group said the noise blasts weren't that unpleasant. That's understandable because the drug reduces pain.
    But they also said the blasts wouldn't be that unpleasant for someone else. That's where the lack of empathy comes in again.

    Figuring out the meaning

    What does this mean?
    "We don't know why acetaminophen is having these effects, but it is concerning," said Way, the co-author.
    The findings are consistent with a 2004 study that found that the part of the brain that's activated when you're feeling pain is the same part activated when you're picturing someone else feeling the same pain.
    It stands to reason that if acetaminophen dulls your pain, it'll dull that other sensation, too.
    So, let's recap what the Ohio State researchers have concluded: The drug numbs pain but also pleasure and compassion.
    That's a pretty big deal, considering about 52 million Americans use a medicine containing acetaminophen every week.
    Next up, the researchers take on that other popular OTC medicine: ibuprofen.