MEDICAL MATTERS: Is the placebo just a trick of the mind or can it really benefit patients, asks Dr Muiris Houston
THANKS TO all of you who responded to the questions about placebos which I posed some weeks back. There were some interesting replies, more of which later.
Writing in last week's British Medical Journal (BMJ), Wendy Moore writes that throughout history, doctors have derived much pleasure from demonstrating the placebo effect, especially when it is used to undermine unorthodox treatments.
In the 18th century, Dr John Hunter did not believe that mercury, the standard treatment for gonorrhoea, worked. He gave several unsuspecting patients pills made from bread. "The patients always got well," he reported with some satisfaction.
Traditionally, doctors have looked at homeopaths with a certain disdain, based on an incredulity that potions with microscopic elements could be scientifically effective.
Back in 1829, physicians ran a large trial among army patients in St Petersburg.
They divided the patients into three groups to receive conventional treatment, homeopathic remedies and placebo bread pills.
Unsurprisingly, the placebo patients did best. Mind you, the conventional treatment involved bloodletting, in which the doctors retained a dubious faith.
Separately, Dr Nicholas Christakis, professor of medical sociology at Harvard Medical School, wrote a thoughtful piece in how we judge whether drugs work or not. The US medic argues that to say a drug works on the basis of clinical trial is "naive simplification".
"(A) problem that has received far less attention is that when patients say a drug 'works', they typically mean something quite different from what doctors mean. Patients mean that most people respond to the drug. This, however, is rarely the case."
Prof Christakis's thesis is that most prescribed drugs have no effect in most patients. He suggests we look at the issue from the perspective of how often placebo "works".
"Imagine that a drug worked 20 per cent of the time in a trial, compared with 5-10 per cent for a placebo. This is the case for drugs ranging from anti-hypertensives to cancer chemotherapy. Such a difference in a [drug] trial corresponds to an enormous effect.
"However, most patients taking such drugs would not benefit - they would hardly think that the drug 'worked'."
The professor quickly adds that this is not to say that drugs evaluated in randomised control trials do not work. They do.
But he reckons both patients and doctors should be vigilant about the possibility that the drug may have no effect in any one person and be ready to consider the need to switch or stop taking the drug. Christakis argues we need protocols to assess a patient's response as part of the formal evaluation of new drugs.
"Just because drugs work in trials does not mean they will work in our patients. In fact, we can often expect that they will not work at all," he concludes.
And so to the placebo scenario, which went like this:
You have been suffering with widespread muscle aches for some months. All medical tests are normal. Your doctor offers to prescribe a sugar pill, which he says has worked for patients with similar symptoms.
1. Would you agree to his proposal?
2. Would you consider his approach unethical?
3. Would you respond differently if the placebo contained an active ingredient such as a vitamin?
Most readers said they would accept the sugar pill prescription. One observed she would prefer to be "lied to" even though this would pose ethical problems. The majority of respondents did not think prescribing a placebo could be considered unethical. "I'd be okay with receiving a sugar pill or saline injection without knowing they were inert, if the doctor has a sound basis for believing they would help," wrote another.
The option of a vitamin placebo was more controversial. Some preferred it to the inert version, while others who were happy to take a sugar pill would not take a vitamin one.
"Even though I don't think vitamin pills are overly useful . . . the thought that 'vitamins are good' would probably still be lurking in the back of my mind, meaning that it might help if I knew that the alternative was a sugar pill," was one interesting comment.
Inevitably, some of you were having none of it, as this response illustrates: "To me a placebo is tricking the mind; therefore none of these questions would make any sense." Touché. I appreciate the forthright response.