By Pat Anson, PNN Editor

We’ve learned some weird things about acetaminophen in recent years. The pain reliever not only helps treat headaches and fevers; it also appears to dull human emotions and have other psychological effects.

A new study at The Ohio State University suggests that acetaminophen could even make you more likely to go sky diving or bungee jumping off a tall bridge.

"Acetaminophen seems to make people feel less negative emotion when they consider risky activities - they just don't feel as scared," says co-author Baldwin Way, PhD, an associate professor of psychology at OSU.

Way and his colleagues enrolled 189 college students in the study, giving them either 1,000 mg of acetaminophen (the recommended dose for a headache) or a placebo that looked the same. Participants were then asked to rate on a scale of 1 to 7 how risky they thought various activities would be.

Students who took acetaminophen were more likely to rate bungee jumping, taking a skydiving class, and walking home late at night in an unsafe part of town as less risky than those who took the placebo. They were also less likely to view speaking up about an unpopular issue at work and playing in a high-stakes poker game as risky.

In short, the study found that acetaminophen makes people more likely to take risks, which is not inconsequential when you consider that about 50 million Americans take acetaminophen every week. The pain reliever is the active ingredient in Tylenol, Excedrin and hundreds of other pain medications, as well as cough, cold and flu remedies.

The OSU study, published in the journal Social Cognitive and Affective Neuroscience, was funded by a $500,000 grant from the National Science Foundation, a federal agency. It adds to a growing body of research that found acetaminophen and other over-the-counter pain relievers have psychological effects on humans.

“With nearly 25 percent of the population in the U.S. taking acetaminophen each week, reduced risk perceptions and increased risk-taking could have important effects on society,” said Way. "We really need more research on the effects of acetaminophen and other over-the-counter drugs on the choices and risks we take.”

Burst Balloons

To test their theory, OSU researchers conducted an experiment to see if volunteers would take more risks while inflating a virtual balloon on a computer screen. Participants clicked a button on a computer to inflate the balloon, earning virtual money as a reward each time they did.

"As you're pumping the balloon, it is getting bigger and bigger on your computer screen, and you're earning more money with each pump," Way explained. "But as it gets bigger you have this decision to make: Should I keep pumping and see if I can make more money, knowing that if it bursts, I lose the money I had made with that balloon?"

People who took acetaminophen were more likely to keep on pumping and had more burst balloons.

"If you're risk-averse, you may pump a few times and then decide to cash out because you don't want the balloon to burst and lose your money," said Way. "But for those who are on acetaminophen, as the balloon gets bigger, we believe they have less anxiety and less negative emotion about how big the balloon is getting and the possibility of it bursting."

Previous research at OSU found that acetaminophen seems to dampen human emotions. Student volunteers who took acetaminophen had fewer emotional highs and lows, and felt less empathy for the physical and emotional pain of others. Other studies have linked acetaminophen to hyperactivity and behavior problems in children.

It’s not just acetaminophen. A 2018 review of studies found that ibuprofen and other over-the-counter pain relievers can also dull your emotions and cognitive senses.

A recent study of calls to U.S. poison control centers found a significant increase in suicide calls involving acetaminophen, ibuprofen and other OTC analgesics.

Excessive use of acetaminophen -- also known as paracetamol – can lead to liver, kidney, heart and blood pressure problems. Acetaminophen overdoses are involved in about 500 deaths and over 50,000 emergency room visits in the U.S. annually.