Paracetamol doesn’t just ease your headache – it also influences your decision-making. Not only are people more likely to take risks after being given the pain-killing drug, they’re also less likely to see potentially dangerous activities as risky in the first place.
Paracetamol, the world’s most widely-used painkiller, has been around for more than 70 years, and is deemed safe enough to be sold over-the-counter. Indeed, around 200 million packs of it are sold each year in the UK. The pharmacology and toxicology of paracetamol are well-understood by scientists, and because of its ubiquity in pharmacies and supermarkets, we tend to think we know what its effects are. We are wrong.
A recent study by researchers at Ohio State University, published in the journal Social, Cognitive and Affective Neuroscience, has found that taking paracetamol is likely to change your judgment, decision-making, and behaviour, making you more willing to take risks.[1]
This finding came about by using the Balloon Analogue Risk Task. The BART is a well-validated task in behavioural psychology that captures differences in sensation-seeking, impulsivity, and deficiencies in behavioural restraint. [2] In this virtual task, participants can earn money by inflating a balloon on a computer screen with key presses. Every additional key press pumps up the balloon a little bit more, earning participants more money in the process. But if they pump too many times, the balloon bursts, and they lose all the money they’ve earned on that balloon. Participants always had the option to play it safe and bank the money they’d earned so far. As such, every additional pump represents a risk: you might earn a little more money, but you could lose everything.
The researchers found that, compared to participants who were given a placebo, those who were given 1,000mg of paracetamol - the standard, clinically approved dose - were more likely to take risks. Across 30 balloons, those in the paracetamol condition pumped up their balloons more times, bursting more of them in the process.
This surprising result could come about for a number of reasons: the paracetamol may have inhibited effective learning about the behaviour of the balloons in the task, or might have made participants less able to monitor their own errors. But the researchers also included another task that makes either of these explanations unlikely.
After taking the paracetamol or placebo, participants were also asked to report their gut-level feeling about the riskiness, and the potential benefits, of a number of activities. Although there was no difference between groups on the perceptions of potential benefits, those who had taken paracetamol rated activities like ‘driving a car without a seatbelt,’ ‘going down a ski run that is beyond your ability,’ and ‘walking home alone at night in an unsafe area of town’ as less risky, compared to those who were on placebo.
These surprising effects may be down to the one thing everyone knows about paracetamol: it’s a pain-killer. But paracetamol is a pain-killer in a far broader sense than you might think. As well as soothing headaches, period pains, and discomfort after dental surgery, paracetamol eases the pain of social rejection, of contemplating your own death, and reduces distress at other people’s suffering. [3][5]
The researchers at Ohio State propose that these ‘pain’-killing aspects of paracetamol explain its effect on risk-taking. We might like to think of ourselves as rational decision-makers when it comes to risk, making choices on the basis of a cold, detached calculation of the probabilities of various outcomes. In reality, to some greater or lesser extent, how we feel about a risk, rather than simply what we think about it, plays a big part in whether we walk home alone, drive without a seatbelt, or pump up the balloon one more time. The risks faced by our ancestors were often the kind that required quick, rather than perfect, decision-making, and while careful deliberation is slow, emotional responses come on fast.
By blocking the negative emotional signals associated with risk when contemplating whether to pump the balloon one more time, paracetamol led participants to take more risks, and in turn to burst more balloons. Likewise, when imagining the riskiness of various activities, the muting of negative affect meant that those on paracetamol perceived less risk involved.
Further research will be needed to understand the precise mechanism of action that leads to these surprising results. But whatever the cause, the findings themselves should be enough to give us pause for thought. Taking risks isn’t necessarily bad per se. And a few more virtual balloons being popped might not seem like a particularly consequential outcome from taking a dose of paracetamol. But consider the fact that billions of those doses are taken each year. What would it mean for a large portion of the population to be even 0.1% less risk-averse in their decision-making? We know that risk-taking propensity is known to play a role in the incidence of traffic incidents, and in fact participant behaviour on the BART is known to correlate with behaviours that influence the risk of traffic injury. [6]
It’s too early to say if paracetamol exerts an effect on risk-taking out in the real world, though this could be investigated experimentally with a driving simulator, or by reviewing toxicology screens after crashes. In the meantime, people with mild COVID-19 symptoms will be taking paracetamol to ease their discomfort, and, perhaps, will decide that it’s not so risky to head out to that house party after all.
Author: Edward Jacobs, DPhil Psychiatry, Somerville College. Twitter; twitter.com/eddietalksdrugs Website; psychedelicethics.com
1. Keaveney, A., Peters, E., & Way, B. (2020). Effects of acetaminophen on risk taking. Social cognitive and affective neuroscience, 15(7), 725-732.
2. Lejuez, C. W., Read, J. P., Kahler, C. W., Richards, J. B., Ramsey, S. E., Stuart, G. L., ... & Brown, R. A. (2002). Evaluation of a behavioral measure of risk taking: the Balloon Analogue Risk Task (BART). Journal of Experimental Psychology: Applied, 8(2), 75.
3. DeWall, C. N., MacDonald, G., Webster, G. D., Masten, C. L., Baumeister, R. F., Powell, C., ... & Eisenberger, N. I. (2010). Acetaminophen reduces social pain: Behavioral and neural evidence. Psychological science, 21(7), 931-937.
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5. Mischkowski, D., Crocker, J., & Way, B. M. (2016). From painkiller to empathy killer: acetaminophen (paracetamol) reduces empathy for pain. Social cognitive and affective neuroscience, 11(9), 1345-1353.
6. Vaca, F. E., Walthall, J. M., Ryan, S., Moriarty-Daley, A., Riera, A., Crowley, M. J., & Mayes, L. C. (2013). Adolescent Balloon Analog Risk Task and behaviors that influence risk of motor vehicle crash injury. Annals of advances in automotive medicine, 57, 77.