Imagine you are at a doctor’s office, about to undergo a small procedure, like the removal of a mole or the insertion of an IUD (‘spiraaltje’): for some people very painful, while for others quite manageable. You are not sure exactly how much pain you should expect. How can you prepare yourself? And what should the doctor tell you about the pain you are about to experience? One way to find out what happens when people have pain expectancies is to test this in an experiment at a lab.

We know from previous experimental research that our expectations of pain guide the physical sensation. You have probably heard of the placebo effect: expecting that something will benefit you or relieve your pain can actually affect your physical symptoms and alleviate the discomfort. Placebo effects have a counterpart – nocebo effects– that are responsible for making you feel worse if your expectations are negative.

If you think about these effects, you might conclude that simply having positive expectations—like “the procedure won’t hurt at all”—is the way to go. And when you consider the influential Bayesian theoretical models, such as predictive coding, it seems even more convincing: the stronger and more certain your positive expectations are, the more beneficial they should be. However, it’s not all that simple.

At Leiden University’s unit of Medical, Health, and Neuropsychology, we ran a series of experimental studies to examine the effects of pain prediction on both pain and affective responses like trust, uncertainty, and disappointment. The initial two experiments, in which healthy volunteers were subjected to heat pain, showed us that while cues providing moderate and strong underprediction of pain did cause pain relief, they also caused uncertainty and undermined trust.

Two subsequent experiments, in which both the magnitude and certainty of pain predictions were manipulated, further built on these findings. In these experiments, in which pain was induced by electrical stimuli, stronger underprediction of pain did not necessarily reduce pain more than more moderate underprediction; however, stronger underprediction was associated with increased disappointment. In other words, having overly positive expectations has limited benefits and can backfire.

But how do we know exactly what someone will experience? Since pain experiences vary from person to person and moment to moment, one never truly knows what to expect. Therefore, we explored what would happen if someone received a precise pain prediction versus being provided with a range. Contrary to our hypotheses, precise predictions did not result in greater pain relief than uncertain ones, and they were generally linked to higher levels of disappointment.

These studies suggest that while positive expectations can help reduce pain, being overly optimistic offers no additional benefit. In fact, it is risky for a healthcare provider to overstate their expectations, as that can lead to uncertainty, disappointment, and, perhaps worst of all, loss of trust in them. Allowing for some uncertainty about the pain one may experience could be more helpful for those preparing to undergo a potentially painful procedure at the doctor’s office.

In everyday clinical practice, a doctor can’t truly know how painful something will feel for you; only you can know that, once you experience it. However, you may still want an estimate of the pain level. How should the doctor communicate this uncertain information? Again using electrical stimuli, we compared three ways of presenting uncertain pain expectations, with participants imagining hearing the information from a medical professional. Simply saying “I don’t know” - while inherently true - could unintentionally worsen the recipient’s pain. It might give the impression that the professional lacks the expertise and compassion a patient needs in a distressing situation. Instead, if the professional explains that the pain experienced varies widely from person to person, or if they express that they cannot say whether you will find the procedure non-painful or highly painful, this can reassure you and increase your trust, leading to a better overall experience. This may be because the indirect way of expressing uncertainty relates to what the doctor sees in clinical practice, implying their expertise.

Our advice would be to maintain a positive but realistic outlook, while leaving some space for uncertainty. So, when you are about to visit a doctor to undergo a procedure that may be painful, you might trust the doctor’s reassurance that it will be okay, while acknowledging that pain can vary from person to person.