Question: Why do placebo effects have such a large impact?

Helen Frost answered on 16 Jun 2017:

Fantastic question Scarlett!

The placebo effect is a really interesting phenomenon, and it shows the power of the mind. It’s important to remember that whenever we feel or sense anything – the heat from a candle when you put your finger too close, a view from the window, a voice talking to us – all of that information is processed by our brains, and then our brains makes us think that we are feeling it from the different parts of our bodies. So you think you feel the burning heat in your hands, but actually you’re feeling it in your brain, and your brain tells your hand to move away, by telling you it hurts. But our brain does all that without us being aware – that’s subconscious.

The placebo effect shows how strongly our conscious mind can influence our bodies, firstly in perhaps making us feel more sick than we really are and secondly in telling us that we feel better once we’ve taken medicine. It’s a bit like when you were a child and you fell over, did your parents kiss you to make you feel better? Of course logic tells us that a kiss can’t make a grazed knee go away, but the distraction and the comfort are really powerful ways to stop you ‘feeling’ the pain so badly.

There have been studies that showed that if a person expects to see a particular change, then it is more likely to happen. In medicine, it has even been shown that the expectation of receiving a drug can cause biochemical changes inside our cells. Our conscious brain can literally convince our cells to behave differently, because it thinks we’re getting a medicine. For example, there was a study where volunteers were told they were being given a stimulant, like coffee, but in fact they weren’t. After a short period of time, the volunteers’ heart rates went up, their blood pressure increased, their pupils dilated and they started breathing more quickly.

It’s pretty amazing stuff, and it’s why we have to have a placebo control in any clinical trial, because we need to know how much of the effect is caused by the drug, but how much of it is caused simply by the knowledge that you’re taking part in a clinical trial.