A recent comment to a post of mine (by a well-known and experienced German alt med researcher) made the following bold statement aimed directly at me and at my apparent lack of understanding research methodology:
C´mon , as researcher you should know the difference between efficacy and effectiveness. This is pharmacological basic knowledge. Specific (efficacy) + nonspecific effects = effectiveness. And, in fact, everything can be effective – because of non-specific or placebo-like effects. That does not mean that efficacy is existent.
The point he wanted to make is that outcome studies – studies without a control group where the researcher simply observe the outcome of a particular treatment in a ‘real life’ situation – suffice to demonstrate the effectiveness of therapeutic interventions. This belief is very wide-spread in alternative medicine and tends to mislead all concerned. It is therefore worth re-visiting this issue here in an attempt to create some clarity.
When a patient’s condition improves after receiving a therapy, it is very tempting to feel that this improvement reflects the effectiveness of the intervention (as the researcher mentioned above obviously does). Tempting but wrong: there are many other factors involved as well, for instance:
- the placebo effect (mainly based on conditioning and expectation),
- the therapeutic relationship with the clinician (empathy, compassion etc.),
- the regression towards the mean (outliers tend to return to the mean value),
- the natural history of the patient’s condition (most conditions get better even without treatment),
- social desirability (patients tend to say they are better to please their friendly clinician),
- concomitant treatments (patients often use treatments other than the prescribed one without telling their clinician).
So, how does this fit into the statement above ‘Specific (efficacy) + nonspecific effects = effectiveness’? Even if this formula were correct, it would not mean that outcome studies of the nature described demonstrate the effectiveness of a therapy. It all depends, of course, on what we call ‘non-specific’ effects. We all agree that placebo-effects belong to this category. Probably, most experts also would include the therapeutic relationship and the regression towards the mean under this umbrella. But the last three points from my list are clearly not non-specific effects of the therapy; they are therapy-independent determinants of the clinical outcome.
The most important factor here is usually the natural history of the disease. Some people find it hard to imagine what this term actually means. Here is a little joke which, I hope, will make its meaning clear and memorable.
CONVERATION BETWEEN TWO HOSPITAL DOCTORS:
Doc A: The patient from room 12 is much better today.
Doc B: Yes, we stared his treatment just in time; a day later and he would have been cured without it!
I am sure that most of my readers now understand (and never forget) that clinical improvement cannot be equated with the effectiveness of the treatment administered (they might thus be immune to the misleading messages they are constantly exposed to). Yet, I am not at all sure that all ‘alternativists’ have got it.