tl;dr version by Ratner and colleagues:
"In many ways, the reviewed findings are alarming. Consumers assume that when they take an over-the-counter pain medication, it will relieve their physical symptoms, but they do not anticipate broader psychological effects."
Info from the study:
"Once in the laboratory, participants provided written informed consent and then were randomly assigned to consume 1,000 mg acetaminophen (n = 59) or a placebo (n = 55) in liquid form, using double-blind drug administration procedures. Solutions were stored in masked containers, preventing experimenters from learning about the nature of the solution, while participants were told they would be receiving either acetaminophen or placebo but not which type of solution. Following recommendations from previous research on absorption timing of acetaminophen (Møller et al., 2000; Randles et al., 2013; Durso et al., 2015), we waited 1 h before administering our measure of positive empathy and other dependent variables of interest. For additional procedural details and measures not germane to the current research questions, see Mischkowski et al. (2016)."
"As predicted, acetaminophen reduced positive empathy. When reading scenarios about various protagonists having pleasurable experiences, participants under the influence of acetaminophen experienced less empathic affect compared to participants who had consumed a psychologically inert placebo. In contrast, acetaminophen did not reduce empathic perceptions, and an exploratory mediation model in which empathic perceptions accounted for the effect of acetaminophen on empathic affect failed to receive empirical support. Acetaminophen’s effects on positive empathy measures held regardless of whether participants assumed that they had consumed acetaminophen or a placebo. Finally, general positive or negative affect did not account for acetaminophen’s effects on positive empathy."
"Finally, our findings have important practical implications. Positive empathy provides part of the “social glue” from which interpersonal bonds are built and strengthened (Morelli et al., 2015). As such, taking pleasure from the good fortune of others fosters interpersonal connection, trust, and – ultimately – prosocial behavior (Reis et al., 2010; Morelli et al., 2014; Andreychik and Migliaccio, 2015), thus providing important societal benefits. These benefits have to be viewed in the context of the amount of people regularly consuming acetaminophen. An estimated quarter of all US American adults take a drug containing acetaminophen every week (Kaufman et al., 2002). It is thus possible that the pervasive use of acetaminophen among Americans may substantially reduce these benefits. However, there is currently no research on the relationship between acetaminophen usage and reduced prosocial behavior in the USA. This research gap needs filling."
https://www.frontiersin.org/articles/10.3389/fpsyg.2019.00538/full
