I just came across
this systematic review which found that the measured placebo effect in ME/CFS patients was much lower than predicted, and lower than in some other medical conditions.
It is really astounding what passes for publishable research in this area.The writers of this publication don't even seem to have a basic grasp of what the placebo effect is.
The paper defines the 'placebo effect' as an improvement in any 'control' group in any MECFS treatment study. That included proper double-blinded placebo groups (you know those taking a sugar drug but not knowing it), non-blinded control groups received a non-target treatment, like specialist medical care or 'relaxation therapy' or the like. It also included people who got nothing and knew they got nothing.
Then they measured how much improvement these groups showed. Not much.
Then they went on to conclude that MECFS patients are resistant to expectancy effects!
But spontaneous improvement rates do not equal expectancy effects. Spontaneous improvement is an observation, and it can have many causes. Expectancy effects are only one of the possible reasons why spontaneous improvement occurs.
Others are:
* natural fluctuation in symptoms
* spontaneous remission
* regression to the mean (the fact that people often enrol in studies when they are feeling particularly bad, so there will be a natural trend for thing sot be not so bad several months later).
The rate of spontaneous improvement in a control group will depend on a lot of things:
* How 'generous' the outcome measure is. Using the measure of overall improvement presented in the PACE Lancet paper, a whopping 45% of usual medical care patients improved!
* The degree to which symptoms fluctuate. Diseases that fluctuate a lot will tend to show more improvement in your control group.
* Time to diagnosis. If the disease is diagnosed quickly, there will likely be a greater incidence of improvement than if the disease takes long time to diagnose (and MECFS takes at least 6 moths, and in most cases, years).
This awful 'placebo' paper has been used by various pro-PACE authors to argue that it was okay for PACE to upsell CBT and GET to the patients that got it. It makes no difference, you see, because MECFS patients are immune to the placebo effect!
Astoundingly bad science.