Should doctors withhold the truth about the effects of drugs?

If you are taking a drug and believe it carries side effects, than that belief can make you more likely to experience those side effects

The nocebo effect is a real and powerful psychological effect that occurs in lots of situations

The nocebo effect is a real and powerful psychological effect that occurs in lots of situations


In an ideal world we would all like our doctors to tell us the truth about the medicines they prescribe. After all, we trust them to act in our best interests and look after our health. But what if withholding information is actually in our own best interests?

That is the dilemma facing some doctors when it comes to prescribing medications that come with side effects, because research has shown that telling someone they might experience side effects from taking a drug can actually increase the likelihood of them actually experiencing them.

“I know it sounds strange, but it’s perfectly true,” said Dr Zelda Di Blasi, co-director of an MA course in positive and coaching psychology at UCC.

“This phenomenon is known as the nocebo effect, and it’s closely related to its better-known cousin the placebo effect. The term means “I shall harm” [as opposed to placebo’s “I shall please”] in Latin, and it’s a real and powerful psychological effect that occurs in lots of situations.

“The placebo effect occurs when someone expects something positive to happen – like a medicine or treatment to improve an illness they might have – and actually experiences that even though they’ve been given a sham medication for testing purposes.

“The nocebo effect, then, is the opposite – it’s the effect that happens when someone expects something negative to happen.

“In the same way you can experience a placebo effect if you take a medication and believe it will help you, the opposite can also happen. If you are taking a drug and believe that it carries side effects than that belief can make you more likely to experience those side effects.

“We’ve found it takes place in particular in placebo-controlled clinical trials where people are on drugs for depression and arthritis, and they’ve experienced what they thought were side effects despite not taking the actual medication.”


The usual way we explain this is that it is a mix of expectation and conditioning, but it seems to be just as powerful as the placebo effect.

“It’s fascinating. Consider the diagnoses that a doctor gives. Ethically you couldn’t study it for real, but if a doctor told you that you had three months to live, what kind of effect would that have on your actual life expectancy, above and beyond your actual medical condition? Who wouldn’t want to know about that?”

In a 2012 paper entitled To Tell the Truth, the Whole Truth, May do Patient Harm: the Problem of the Nocebo Effect for Informed Consent, Harvard’s Dr Rebecca Erwin Wells examined the issue of this problem for doctors.

Amongst the evidence for this effect she cited studies for a trial for aspirin for unstable angina in which people who were told they might have gastrointestinal side effects were six times more likely to experience them than if they were not told.

Likewise, in a study into a medication that had a side effect of erectile dysfunction, only 3.1 per cent of those that were not told about it experienced the problem, while 31.2 per cent of those who were told did.

Other studies have shown that those people who were told that a procedure would involve “pain” reported more pain than those who were told they would experience a “cold sensation”.

“In all these examples information changed the adverse effect profile. Furthermore, some have speculated that the rates of the nocebo effect seen in clinical trials may be an underestimate of the true prevalence as patients who are reluctant to receive novel medical treatments due to anxiety or mistrust and may be more susceptible to the nocebo response, and might avoid participation in a clinical trial,” said Wells.

Interestingly, people only seem to experience the side effects that they are told about and not ones they are not.

Yet some people’s experience of the nocebo effect is so significant that between 4 per cent and 26 per cent of patients in anti-depressant medication trials on placebo drugs actually withdrew from the trials because of “perceived adverse events”.

Context effect

Di Blasi did her doctoral thesis on the placebo effect, and has spent much of her career studying the way in which expectations can influence our lives.

“The placebo effect is any improvement that comes from having taken a tablet that has no pharmacological effect on whatever the condition is, but I prefer to call it the context effect because it happens for a variety of contextual reasons.

“For example, whether you experience it or not has a lot to do with the relationship you have with the doctor, the trust that you have in them and their expertise, and the expectation you have that you will improve based on what your doctor has to say and the effect you believe a treatment will have.”

In her doctoral research Di Blasi performed a systematic review of randomised clinical trials that were placebo-controlled. She was looking for evidence to show it was possible to activate the placebo effect deliberately in a doctor-patient relationship.

In other words, if the placebo effect is real how can it be harnessed for good, and in turn how can the nocebo effect be avoided?

“I looked at the difference between cognitive care, which is changing the way people think about the care they receive or their condition, and emotional care, which is more about the doctor’s warmth, empathy and care,” she said.

“For example, if the doctor is cold, detached and formal, what is the effect? We found that if the doctor was warm and caring and also increased the patient’s expectations, then that seems to predict the placebo effect being triggered.”

Certain conditions

Just how powerful is the placebo effect in action? It turns out it is particularly powerful in certain conditions.

“It can have a pronounced effect on depression, pain, stress, irritable bowel syndrome, even anxiety and sleep disorders. There is also some very interesting research that has been done into the effect of the placebo effect in clinical trials on arthroscopy where there is osteoarthritis of the knee and it seems to have a particularly powerful effect there,” said Dr Di Blasi.

“Mostly we find it where the condition is at least partially subjective in nature because each person’s perception of their condition is a little different. There are standardised measures for pain and depression for example, but people have different pain tolerances.”

And what of the dilemma facing doctors about whether to tell patients about side effects or not?

Rebecca Erwin Wells suggests that it is possible for doctors to skirt the line between primum non nocere (“above all do no harm”) and the important principle of informed consent.

“This involves taking into account the possible side effects, the person being treated, and the disease involved to tailor the information provided about medication side effects to provide the most transparency with the least potential harm.”

The trick, she suggests, is to opt for contextualised informed consent. There is no need to warn people about vague low-level non-specific side effects like difficulty concentrating, drowsiness, nausea, dizziness, fatigue and so on. Instead the doctor should advise the patient to contact them with any new or unusual symptoms.


“If the patient does call back with a vague, non-specific symptom the physician can then evaluate the patient to see if the reaction is due to the medication or due to an unrelated process independent of the new medicine.”

The overall take-away from looking at the role of the placebo/nocebo effects, according to Dr Di Blasi, is that medical science is still figuring out how various aspects of the human condition interact.

“The reality is that there is a very strong mind-body connection. How we think about health and illness has a serious effect on how we experience these conditions. It’s important that doctors understand this connection as that will be beneficial in terms of empowering people.

“It’s my opinion that the biomedical model doesn’t really stand on its own feet anymore, and it makes more sense to think in terms of a bio-psycho-social model instead, because all these factors interact with each other.

“Attributing improvements in health solely to the benefits of drugs takes away from the healing that comes from within the person and from within the context that the healing takes place in.

“Ideally you want to have a good doctor, a good relationship with that doctor and a good level of knowledge yourself.”

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