Thursday, April 7, 2016

What is the therapeutic illusion?

Some hairless cats I have been hanging out with...

Last week a colleague sent me a thought-provoking article about the therapeutic illusion in the field of human medicine.

The therapeutic illusion is related to a more generalised illusion – the illusion of control. It’s a human tendency to infer causality where none exists. For example, gamblers routinely overestimate the control they have over outcomes. Volunteers in experiments who were asked to press a button to get a panel to light up felt that they had cracked the code once it did, even though the outcome was random. Human beings, in other words, have a tendency to overestimate the impact of their actions.

The therapeutic illusion is the illusion of control applied to treatment modalities. And physicians suffer from it too. So they overestimate the impact of treatment of conditions like back pain and cancer.

The illusion is reinforced by confirmation bias – where we selectively look for evidence that supports our existing beliefs.

It’s not always a BAD thing. The illusion may increase confidence of physicians which can rub off on patients and other health care providers. And humans in general are more motivated to act if they believe their actions matter.

But the therapeutic illusion can lead to inaccuracies in assessing the efficacy of a particular treatment. And the author of the paper is concerned that the therapeutic illusion may lead to over-treatment.

So in a veterinary setting, for example, it is possible, in some cases, for some animals to get better in spite of – not because of treatment. Or because of one component of treatment and not another. But it can be hard for us to see this. 

For example, this week I spoke to some clients whose dog had cancer. A number of treatments were performed including surgery, antibiotics, anti-nausea medication and a novel drug therapy – all administered or at least initiated on the same day. The owners swore that the novel drug cured their dog. Their vet wasn’t so sure. The cure may have been a result of the surgery, or a combination of some or all of the treatments. This is why controlled studies are needed. 

Evidence-based medicine means we need to constantly question our evaluation of treatment success.

David Casarett provides two tips to counter the therapeutic illusion:
  • Before you conclude that a treatment was effective, look for other explanations.
  • If you see evidence of success, look for evidence of failure, i.e. test assumptions of therapeutic efficacy by looking for negative outcomes.

But he warns that over-thinking can have negative impacts too. If physicians doubt their own effectiveness, they might under-treat – the harms of which could be the same or worse than over-treating. It can be a fine line and sometimes hard to judge.

The paper does not suggest that we have no control over therapeutic outcomes – far from it. But it does argue that we can improve outcomes and contribute to rational, evidence-based medicine by questioning our assumptions.

Check out our previous post on evidence based medicine at this link