Researchers have found that the popular over-the-counter pain reliever acetaminophen may not only relieve a person's pain, but may also blunt positive emotions. Results of the study were published online in the journal Psychological Science.

In the study,  participants were asked to evaluate both negative and positive images from the International Affective Picture System. Photographs ranged from extremely unpleasant (crying, malnourished children), to neutral (cow in a field) to very pleasant (young children playing with cats). Participants were then asked to rate the images on a scale of -5 (extremely negative) to +5 (extremely positive); photos were viewed again and participants were asked to rate their emotional reaction from a scale of 0 (little or no emotion) to 10 (extreme amount of emotion).

Compared to those who took placebo, individuals in the acetaminophen group evaluated unpleasant images less negatively and pleasant ones less positively. The acetaminophen group also rated positive and negative images as less emotionally arousing, with an average level of emotion of 5.85 when they saw extreme photos. Those in the placebo group rated their level of emotion relatively high (average score 6.76) when they saw emotionally jarring photos. 

The results of this study were further reproduced in a second study, however when participants were asked to report on the extent of color saturation in the images, judgments of color content were similar regardless of drug condition.

The authors conclude that acetaminophen may have a general blunting effect on a person's evaluative and emotional processing. This study also offers support to a new theory that says common factors may influence how sensitive a person is to positive and negative life events. It is not known whether other pain relievers such as ibuprofen and aspirin have the same effect.

For more information visit OSU.edu.

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