Acetaminophen seems to do more than just lower a fever or get rid of a nasty headache -- and some of its effects are pretty bizarre.
Previous research has shown that the over-the-counter painkiller (the active ingredient in Tylenol) can ease the psychic pain of rejection and even tamp down feelings of existential dread.
And now a new study suggests that acetaminophen blunts the feelings of pleasure too.
“This means that using Tylenol or similar products might have broader consequences than previously thought,” Geoffrey Durso, the lead author of the study and a doctoral student in social psychology at The Ohio State University, said in a written statement. “Acetaminophen can be seen as an all-purpose emotion reliever."
For the small study, 82 college students took either 1,000 mg of acetaminophen or an identical-looking placebo before viewing a series of photos. Some of the photos were pleasant (e.g. children playing with cats), while others were unpleasant (e.g. malnourished children) and some neutral (e.g. cow in a field).
The students rated each photo for how positive or negative it was on a scale of -5 (extremely negative) to 5 (extremely positive). The students also rated their emotional response to each photo on a scale of 0 (no emotional response) to 10 (extreme emotional response).
What happened? Students who had taken acetaminophen rated both the unpleasant and pleasant photos less extremely than those who had taken the placebo. That is, they rated the negative photos as being less negative and the positive photos as being less positive.
Acetaminophen also seemed to lower the students' emotional response to the photos. While those who had taken acetaminophen reported an average emotional response of 5.85, those who had taken the placebo reported a response of 6.76.
What explains the strange effect?
"At this point, there are more questions than answers," Durso told The Huffington Post in an email.
Several different mechanisms could be involved, according to the researchers.
"Acetaminophen exerts a multitude of effects: changing serotonin neurotransmission in the brain, reducing inflammatory signaling in the brain, or decreasing activation in the brain areas responsible for emotion, for instance -- and any one or combination of these effects could be responsible for the psychological outcomes that we observe on individuals' blunted negative and positive evaluations," Durso said.
The new research was published online April 10 in the journal Psychological Science.