The placebo effect is a very powerful tool in medicine, but also hinders at the same time. It has been shown that the type of placebo can also affect the response: giving a white pill has less of an effect than giving an injection, for example.
Many have found this:
- Drug A will elicit a response of 5 (arbitrary units)
- Placebo will elicit a response of 2
- Placebo and Drug A will elicit a response of 7
Extremely useful! Give someone a lower dose and you are getting a larger response than the drug alone! To continue...
- Infuse (so can't tell when drug has started/stopped) the patient with Analgesic A - pain goes down by 5
- Stop infusion and tell the patient it has stopped - pain resets to baseline
- Start the infusion and don't tell the patient anything - pain drops by 2
- Keep infusion going and tell the patient it's just started - pain drops by 5
- Tell the patient the drug has been stopped, but continue administration - pain goes up by 2, but is still 3 units below baseline: known as the nocebo effect
The nocebo effect can also be of interest - tell the patient that a placebo will give then side-effects, and you find that people get side effects and stop taking the drug! In fact, tell them that they are actually receiving a placebo and they still feel like they're having side-effects!
Placebo effects aren't so useful in clinical drug trials: they can create noise (as if the placebo is having a significant effect, how much of the effect of the drug is due to the drug itself? It might just be the placebo effect!). They can also cause people to drop out prematurely: people take a placebo and think they're having adverse reactions to it due to the nocebo effect, reducing study size and therefore reliability.