The active ingredient in Tylenol might numb people’s emotional reactions, according to a study conducted by researchers from Ohio State University and published in the journal Psychological Science.
“People who took acetaminophen didn’t feel the same highs or lows as did the people who took placebos,” researcher Baldwin Way said.
Notably, the participants in the study did not realize that their reactions had been affected.
“Most people probably aren’t aware of how their emotions may be impacted when they take acetaminophen,” Way said.
Blunts ability to feel strong emotion
The researchers randomly assigned 82 participants to take a single pill containing either a placebo or acetaminophen (also known as paracetamol), which is the active ingredient in Tylenol. An hour later, participants were shown 40 photographs showing images ranging from sad (such as crying children who appeared malnourished) to neutral (such as a cow in a field) to happy (such as children playing with kittens). Participants were asked to rate each image on a scale from positive to negative. They were then shown the same photos again and asked to rate how much emotion each photo provoked in them.
The researchers found that participants who had taken acetaminophen ranked the photos as both “more neutral and less emotionally intense” than those who had taken a placebo.
The Ohio researchers were curious whether acetaminophen was targeting emotions directly or simply interfering with participants’ ability to judge magnitude, such as the magnitude of emotion. Therefore, they repeated the study with another 85 participants, and this time they also asked the participants to rate how much blue there was in each photo. Once again, the participants who took acetaminophen ranked the photos as more neutral and less emotionally intense than those who took a placebo. There was no difference in how the two groups perceived the magnitude of blue, however.
This suggests that Tylenol interferes directly with the brain’s emotional processing capability. The researchers noted that people naturally vary in the way they respond to emotional life events, both positive and negative; perhaps the drug dulls this sensitivity, even in people who tend to be more emotional.
“There is accumulating evidence that some people are more sensitive to big life events of all kinds, rather than just vulnerable to bad events,” lead author Geoffrey Durso said.
Surprisingly, the researchers actually attempted to spin acetaminophen’s emotion-dulling effect as a benefit rather than an alarming adverse effect.
“This means that using Tylenol or similar products might have broader consequences than previously thought,” Durso said of the findings. “Rather than just being a pain reliever, acetaminophen can be seen as an all-purpose emotion reliever.”
Dangerous for your brain and liver
The participants plan to repeat the study on painkillers in the nonsteroidal anti-inflammatory drug (NSAID) family, such as aspirin and ibuprofen. These painkillers function by a different mechanism than acetaminophen, so they might not have the same effect.
Narcotic painkillers such as morphine function by yet another mechanism.
Scientists still do not understand precisely how acetaminophen dulls pain, but evidence is emerging that it may act in part by dulling the brain’s ability to experience distress. A 2009 study found that acetaminophen seemed to dull the emotional pain caused by social rejection. A 2013 study conducted by researchers from the University of British Columbia and published in Psychological Science suggested that it might also blunt the sense of indignation that leads to moral judgments.
In addition to its still poorly understood effects on the brain, acetaminophen is known to be incredibly dangerous to the liver. In fact, acetaminophen is one of the most commonly overdosed drugs in the world, and it is actually the drug that causes the most damage when people overdose on prescription drugs such as Vicodin or Percocet.
In the United States alone, about 60,000 people are hospitalized every year due to acetaminophen-related liver failure.