Researchers studying the commonly used pain reliever acetaminophen or paracetamol have found that it has a previously unknown side effect: it blunts positive emotions. In the study, participants who took acetaminophen reported less strong emotions when they saw both very pleasant and very disturbing photos, when compared to those who took placebos.
Acetaminophen is the main ingredient in the pain reliever Tylenol and is found in more than 600 medicines. 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 at The Ohio State University.
Researchers said the people in the study who took the pain reliever did not appear to know they were reacting differently. The study involved 82 participants, half of whom took an acute dose of 1,000 milligrams of acetaminophen and half who took an identical-looking placebo. Participants then viewed 40 photographs selected from a database (International Affective Picture System) used by researchers around the world to elicit emotional responses. The photographs ranged from extremely unpleasant (crying, malnourished children) to the neutral (a cow in a field) to the very pleasant (young children playing with cats). Participants who took acetaminophen rated all photos less extremely than did those who took the placebo.
In other words, positive photos were not seen as positively under the influence of acetaminophen and negative photos were not seen as negatively. The same was true of their emotional reactions. “People who took acetaminophen didn’t feel the same highs or lows as did the people who took placebos,” researchers said.
The researchers did a second study in which they had 85 people view the same photos and make the same judgments of evaluation and emotional reactions as in the prior study. Additionally, participants in this second study also reported how much blue they saw in each photo. Once again, individuals 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 colour content were similar regardless of whether the participants took acetaminophen or not. The results suggest that acetaminophen affects our emotional evaluations and not our magnitude judgments in general, researchers said. The results appear in the journal Psychological Science.
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