Acetaminophen May Affect Your Emotions

By Sondra Forsyth

Acetaminophen may do more than treat your headache: it could weaken your emotions, researchers have found.

Investigators from The Ohio State University reached that conclusion after conducting two studies.

The first involved 82 participants, half of whom took an acute dose of 1000 milligrams of acetaminophen and half who took an identical-looking placebo. They waited 60 minutes for the drug to take effect.

Participants then viewed 40 photographs selected from a database used by researchers around the world to elicit emotional responses. The images ranged from very unpleasant (malnourished children) to neutral (a cow in a field) to pleasant (children playing with cats).

Results showed that participants who took acetaminophen rated all the photographs less extremely than did those who took the placebo. In other words, they didn’t react as negatively to negative photos or as positively to positive photos. Reaction to neutral photos was the same in both groups.

In a second study, the researchers asked 85 people to view the same photos. Each group was also asked to estimate the amount of blue in the photos.

The outcome was similar to the earlier study. People who took acetaminophen (compared to placebo) had evaluations and emotional reactions to both negative and positive photographs that were significantly blunted. However, judgments of blue color content were similar regardless of whether the participants took acetaminophen or not, according to a release from the university.

The results suggest that acetaminophen affects emotional evaluations and not “magnitude judgments” in general.

Although acetaminophen, the main ingredient in Tylenol, has been in use for 70 years, this is the first time this side effect has been documented, according to the university’s news release.

Previous research had shown that acetaminophen works not only on physical pain, but also on psychological pain. This study takes those results one step further by showing that it also reduces how much users actually feel positive emotions, said Geoffrey Durso, lead author of the study and a doctoral student in social psychology.

“This means that using Tylenol or similar products might have broader consequences than previously thought,” Durso said. “Rather than just being a pain reliever, acetaminophen can be seen as an all-purpose emotion reliever.”

Acetaminophen is the most common drug ingredient in the United States, found in more than 600 medicines, according to the Consumer Healthcare Products Association, a trade group. Each week about 23 percent of American adults (about 52 million people) use a medicine containing acetaminophen, the CHPA reports.

At this point, the researchers don’t know if other pain relievers such as ibuprofen and aspirin have the same effect, although they plan on studying that question, Durso said.

The findings were published in the journal Psychological Science.