Acetaminophen Blunts Emotions

Ohio State University research indicates that acetaminophen appears to have a general blunting effect on patients’ evaluative and emotional processing, regardless of negative or positive valence. Despite common use in the United States for more than 70 years as an ingredient in more than 600 medicines, acetaminophen had not been formally linked with this side effect until the current study, which was published online in Psychological Science.

Whereas prior research found acetaminophen to work on both physical and psychological pain, this study shows that the agent also reduces how much users actually feel positive emotions, according to lead author Geoffrey Durso, doctoral student in social psychology, Department of Psychology, Ohio State University. “This means that using Tylenol or similar products might have broader consequences than previously thought,”he said. “Rather than just being a pain reliever, acetaminophen can be seen as an all-purpose emotion reliever.”

Participants in the study who took acetaminophen did not appear to realize they were reacting differently, according to study co-author Baldwin M. Way, PhD, assistant professor, Department of Psychology and Center for Clinical and Translational Science, Institute for Behavioral Medicine, Ohio State University. “Most people probably aren't aware of how their emotions may be impacted when they take acetaminophen,” he said.

Durso and colleagues conducted two experiments for the study. For each, participants were randomized to acetaminophen 1,000 mg or placebo. After waiting 60 minutes for the medication to take effect, participants were shown 40 photographs selected from a database used by researchers worldwide to elicit emotional responses. Photographs ranged from extremely unpleasant (crying, malnourished children) to neutral (a cow in a field) to very pleasant (young children playing with cats).

For the first experiment, after viewing each photograph, participants rated how positive or negative it was on a scale of -5 (extremely negative) to +5 (extremely positive). They then view the same photos again and rated them based on how much the photos made them feel an emotional reaction, from zero (little or no emotion) to 10 (extreme amount of emotion).

Those who took acetaminophen evaluated unpleasant photos less negatively and pleasant photos less positively that those who took a placebo. Participants who took acetaminophen also rated both negative and positive photos as less emotionally arousing than did those who received a placebo.“People who took acetaminophen didn't feel the same highs or lows as did the people who took placebos,” said Way.

According to Durso, acetaminophen may change how people judge magnitude by blunting their broader judgements of everything, not just those things that would normally illicit an emotional response. For the second experiment, participants viewed the same photos and made the same judgements of evaluation and emotional reactions as in the first experiment, but they also were asked to report on the extent of color saturation in each image. Whereas the evaluations and emotional reactions of those who took acetaminophen were again blunted, their judgements of color saturation were similar to those who took a placebo, suggesting that the drug affects emotional evaluations, not magnitude judgments in general.

Durso said that the team plans to study whether other pain relievers, such as ibuprofen and aspirin, have the same effects as acetaminophen, as acetaminophen is not a nonsteroidal anti-inflammatory drug like many other pain relievers.