By Matthew Warren

The placebo effect is a curious phenomenon. A wealth of literature has shown that inert treatments can not only produce medical benefits like pain relief, but also have cognitive effects like boosting creativity and learning. And while many of those studies involve misleading people into thinking that they are receiving an effective intervention, a new study in Scientific Reports shows that this deception is not always necessary. Researchers have found that taking a placebo can reduce people’s anxiety before a test — even when they know they are taking an inactive pill.

As many as 2 in 5 people experience test anxiety, which can involve physical symptoms like high heart rate and sweating, negative thinking, and even impaired performance or avoidance of the test in the first place. Some sufferers take medications or have psychotherapy — but Michael Schaefer from Medical School Berlin and colleagues wondered whether just taking a placebo could help.

The team recruited 58 university students who were approaching their end of term exams. Half of the participants were given no treatment, while the other half were asked to take two placebo pills per day for two weeks. Importantly, there was no deception involved: the researchers told participants in the placebo condition that their pills were inactive. Before starting the course of treatment, and again at the end, the participants completed questionnaires that measured their level of test anxiety, physical and mental well-being, and self-management skills (for example, coping mechanisms and belief in one’s own ability to succeed).

The control group didn’t show any difference in the measures before and after the treatment period. But the story was different for the placebo group: after “treatment” with the placebo, their anxiety had significantly reduced, and they also showed improved self-management abilities. It wasn’t clear, however, whether these changes had any knock-on effect on exam grades (within the placebo group, participants who showed a greater improvement in their self-management skills tended to achieve higher grades, but this correlation didn’t reach significance).

It’s a mystery how placebos decrease anxiety even when people are aware that they are taking an inert substance, the researchers write. One possibility is that the positive way in which the researchers discussed the intervention with participants may have played a role: participants were told that placebo effects could be “powerful” and that the body may respond automatically. But while the results might seem surprising, they are consistent with previous research that has found “open label” placebos can be effective for conditions like irritable bowel syndrome.

Still, the results are very preliminary. The sample size was pretty small, and it’s unclear whether what seems to be a fairly modest drop in anxiety scores has practical relevance. It would be interesting to see more detailed evidence of exactly how the placebo intervention affected participants — did it alter their negative thinking, for instance, or have more of an effect on physical symptoms of test anxiety?

And even if placebos reduce the kind of anxiety people experience before a test, that doesn’t necessarily mean they work for more chronic anxiety or in other stressful situations. There are, of course, many other ways for dealing with high pressure situations — for more on those, see this week’s feature from Emma Young.

– Open-label placebos reduce test anxiety and improve self-management skills: A randomized-controlled trial

Matthew Warren (@MattbWarren) is Editor of BPS Research Digest