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.


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.

5 Responses to How naïve ‘alternativists’ lead us (and themselves) up the garden path

  • So, German’s do have a sense of humour!

    But note:
    The Shorter Oxford English Dictionary defines ‘efficacy’ as: ‘Capacity to produce effects; power to effect the object intended. A mode of effecting a result (John Locke).’
    ‘Effectiveness’ is: ‘the quality of being effective.’ ‘Effective’ is defined as: ‘That is concerned in the production of effects; having the power of acting upon objects. Concerned with, or having the function of, effecting. That has an effect.’

    New Collins Thesaurus has an alternative word for ‘efficacy’, namely ‘effectiveness.’ Also a synonym for ‘effectiveness’ namely ‘efficacy.’

    It is difficult to differentiate between the meaning of either word.
    Is there any useful distinction between the terms ‘efficacy’ and ‘effectiveness’ as used in day to day healthcare?

    Shifty semantics is a sign of pseudoscience.

    • @Richard
      Indeed, in English the two words approximate to the same meaning, but — if I remember my rudimentary pharmacology properly — medical efficacy measures the ability of a drug to cure a given condition, regardless of other considerations, while effectiveness takes account of ‘real-world’ situations. Things like ease of administration and palatability of drugs, occurrence of side-effects that (reasonably or unreasonably) cause patients not to take the drug, and so on, mean that a drug’s effectiveness is likely to be less than its efficacy. ‘Intention to treat’ analyses in randomized trials are one means of focussing on a drug’s efficacy alone. But in practice it’s often difficult to make clear-cut distinctions between efficacy and effectiveness.
      I think this is what the commenter who provoked this thread was trying to convey. Proponents of Big Snakeoil will argue that their satisfied customers demonstrate the effectiveness of their treatments, but they never seem to design adequate trials to measure effectiveness properly. Prospective, randomized, double-blind comparative trials can be designed to measure either efficacy or effectiveness; but because people are people and not test tubes the behaviour of patients is always capable of marring the outcomes.

      • Agreed, well put.

        So, when using these terms it should be made clear that it is ‘pharmacological efficacy’ being referred to.
        Regular day-to-day usage makes no distinction.

        And it is through that narrow chink of semantic sophistry that slippery scamists slide as the seek to mislead the unwary.

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