If you took a pill that had been prescribed to treat your illness and it alleviated your symptoms, that means the medicine worked – right?
What if you took a complementary medicine from a health food store instead?
Or if you were given a sugar pill and you still felt better?
Medicines, surgery and alternative therapies all inevitably cause some degree of placebo response, but it’s not just the gullible or suggestible who are affected.
Firstly, you might experience what’s known as the Hawthorne Effect.
It goes something like this. If you’ve identified a problem with your health and sought help for it, you will tend to be making other, related decisions which can reduce your symptoms – or your perception of them.
So if you feel your knee becoming sore, you’ll probably tend to use it less and be more careful about what you do. Both may help reduce your pain, independently of the treatment you seek.
Having an involved and attentive health professional to empathise with your concerns will likely strengthen your tendency to get on with life instead of fretting about the pain in your knee and what it might mean.
Secondly, you might succumb to the phenomenon of Regression to the Mean, which is a scientific-sounding way of explaining that any long-term complaint will tend to vary around its average level. Some days it will be a bit worse, other days it will feel a bit better than average.
Our inherent bias is to ignore the good days and focus on the bad. If we string together a few days of worsened symptoms, which will happen at some stage, you might be tempted to try something out of the ordinary – such as alternative therapies – to feel better again.
But the longer the symptom is above or below its long-term average, the more likely it is to begin returning to the usual level.
When this return coincides with the trial of a new treatments you saw on TV or bought over the internet, the treatment seems to work. So you would rationally (but incorrectly) assume you responded to the treatment.
This logic also applies to self-limiting conditions which will last for a set period – whatever treatment is applied – such as back pain or even a cold.
So what proportion of people are likely to experience the placebo effect?
Sham surgery (or placebo surgery) has the biggest placebo response, with some studies reporting positive results in 70% or more of the participants, and long-lasting improvements in function.
This is followed by physical treatments such as acupuncture or Transcutaneous Electrical Nerve Stimulation, and then by pills. Pills can vary from low to high response rates depending on the condition being studied, and active drugs such as morphine can be more effective if delivered openly instead of being hidden.
The size of the placebo effect in psychiatry research appears to be increasing over time, making it harder to trial antidepressant drugs.
This is likely due to more sophisticated study designs which are more sensitive to bias, and to changing community expectations about the effectiveness of the therapies being trialled. It’s not likely to be because people are becoming more suggestible.
Deception is supposedly at the heart of the placebo response, but it seems that even this may be a furphy. The strength of patient-health provider interactions can be such that it’s possible to get relief from symptoms when knowingly taking a placebo, if they are primed appropriately.
Interestingly, the placebo response doesn’t affect everyone. Placebo pain relief is significantly reduced in people with damage to the frontal lobes, such as stroke survivors, brain injury victims or those with dementia.
The placebo response has social, psychological and biological implications that researchers are still struggling to understand. It’s certainly not as simple as being fooled into feeling better.