It’s not unusual to think that, in order for a placebo to work, it’s important that you don’t know it’s a placebo. But what if we told you that wasn’t true. Would that blow your mind? Maybe.

Well, that’s exactly what a study by the University of Basel in Switzerland and the Harvard Medical School in the US have found. Their findings are published in the journal Pain, which is a legitimate journal I swear.

In the study, a heating plate was placed on the forearms of 160 healthy volunteers. The temperature was increased until they could no longer stand the heat, and they were then given a cream to relieve the pain.

One group were given a pain relief cream that claimed to have the active ingredient lidocaine, used to numb tissue, although it was actually a placebo.

A second group had a cream that was clearly identified as a placebo, and they were given a 15-minute talk about the placebo effect. A third group were given an open-label placebo, with no explanation.

Both the first two groups reported a decrease in pain and pleasantness, but there was no such relief for the third group. This suggests that, bizarrely, placebos work even if we know they are placebos, as long as we are told how the effect works.

"The previous assumption that placebos only work when they are administered by deception needs to be reconsidered," said Dr Cosima Locher from the University of Basel, the lead author of the study, in a statement.

Now, this is not the first study to suggest placebos work when we know they are placebos. But as far as we can tell, this is the first to show that being told they are a placebo is not enough – you also need to know how the placebo effect works.

In fact, in this study the volunteers in the third group actually reported more intense and unpleasant pain, suggesting communication and rationale are key when using placebos.

"Openly administering a placebo offers new possibilities for using the placebo effect in an ethically justifiable way," said Professor Jens Gaab from the University of Basel in the statement.