Is the supposed success and popularity of alternative and complementary medicine entirely due to the placebo effect? Do psychologists wisely exploit the placebo effect? How does it work and how do we know whether interventions really work, unaffected by the placebo effect?

Placebo means “to please.” The concept of mind over matter in the world of health has been known for centuries.  Modern research in the area is usually attributed to a paper written in the American Dental Association journal over 50 years ago. Henry Beecher shocked the medical world by claiming that just placebo procedures like giving sugar pills or even sympathetically physically examining the patient would lead to an improvement in 30 percent of patients.

Today, that estimate has increased to between a half to three quarters of patients with all sorts of problems from Asthma to Parkinson’s show real lasting improvements from a range of placebo treatments.

Some believe placebo effects are more effective for psychological rather than physical illnesses.  One important recent study showed that nearly 60% of placebo controlled patients did better than average waiting-list control patients showing the power of the placebo.

Although a placebo is simply defined as a preparation with no medicinal value and no pharmacological effects and active placebo is one that mimics the side-effects of the drug under investigation but lacks its specific, assumed therapeutic effect.

It is possible to distinguish between active placebos which have effects but not on the problem they are meant to cure and inactive effects which have the measurable direct or side effects.

Some have argued that the history of western (orthodox) medicine is a history of placebo.  Prior to the beginning of the twentieth century most medical treatments were inert or toxic.  That is they had no effect or a negative effect.

Placebos administered in an orthodox medical context have been shown to induce relief from symptoms in an impressively wide array of illnesses, including allergies, angina pectoris, asthma, cancer, cerebral infarction, depression, diabetes, enuresis, epilepsy, insomnia, Meunière’s disease, migraine, multiple sclerosis, neurosis, ocular pathology, Parkinsonism, prostatic hyperplasia, schizophrenia, skins diseases, ulcers, and warts.

Pain is the commonest symptom giving rise to a medical consultation and has also been the commonest outcome measure in studies of the placebo effect as well as the impact of placebos on symptoms, placebo effects have also been demonstrated on objective measures of certain bodily processes, including blood pressure, lung funtion, post-operative swelling, and gastric motility.

Adverse effects of placebo administration have also been noted in many studies. These include dependence, symptom worsening (the nocebo effect) and a multitude of side-effects, both subjective (headache, concentration difficulties, nausea, etc.) and objectively visible (skin rashes, sweating, vomiting).

Differences between placebo responders and non-responders have long been of interest. Attempts to spot such differences on socio-demographic characteristics (age, gender, ethnicity, educational level) have generally yielded weak and inconclusive findings.  Other studies have looked at possible individual differences in intelligence and personality. Any patient may benefit from the placebo effect, not just a gullible minority.

One question is what type of placebo works best?  The colour and size of capsules and pills have been repeatedly subject to experimental manipulation, but with little reliable impact.  It does not seem to make much difference.  One researcher reported that for a placebo to be maximally effective it should be very large and either brown or purple or very small and either bright red or yellow.

More serious, "major" or invasive procedures do appear to have stronger placebo effects.  Injections per se appear to have a greater impact than pills and even placebo surgery (where people are cut open and sewn up with little or nothing done) has yielded high positive response rates.

The style of treatment administration and other qualities of the therapist appear to contribute substantially to the impact of the treatment itself.  Those therapists who also exhibit greater interest in their patients, greater confidence in their treatments, and higher professional status, all appear to promote stronger placebo effects in their effects in their patients.

The fascination with placebo effects has led to many ideas and theories as to how they actually work.  All sorts of concepts have been proposed including operant conditioning, classical conditioning, guilt reduction, transference, suggestion, persuasion, role demands, faith, hope, labelling, selective symptom monitoring, misattribution, cognitive dissonance reduction, control theory, anxiety reduction, expectancy effects and endorphin release. At this stage there exists no accepted single account that seems to explain and predict placebo effects. 

Randomized, double-blind, control trials.

The placebo effect is both a blessing and a curse.  A blessing for all therapists irrespective of what treatment they prescribe. They are a curse for scientists who try to evaluate the real effect of interventions. The placebo controlled randomized double-blind study has become the gold standard of scientific research to assess therapy and “discount” any placebo effects.

The idea is that people are randomly sent to different groups, some of which are control groups having no treatment, alternative treatment or placebo treatment.  Further, neither the doctor/scientist/therapist nor the client/patient knows which treatment they are receiving.

The first randomized controlled trial took place soon after World War II.  Patients were randomized to a treated or control group, by consulting sealed envelopes held at a central location.  Bias in allocation was therefore avoided.  The entry criteria were strict and determined prior to the allocation.  Great care was taken to avoid bias from any source.  There was no placebo control though, as it would have meant giving four painful intramuscular injections every day for four months; treated patients were simply compared with untreated patients.  However, the clinical assessment was carried out by independent observers who had no knowledge of the patient’s allocation.  The trial also marked the first attempt to grapple with the ethical issues involved in controlled trials, in that the committee considered it would be unethical not to attempt a speedy, formal evaluation of a potentially fatal disease, presumably as opposed to waiting for an accumulation of clinical experience.

But it wasn’t until 20 years ago that “blinded” studies were introduced.  It was recognised that psychological factors may affect the response to treatment, the patient may be kept ‘blind’ to the nature of the treatment they got.  Psychological factors may also affect the clinician giving the treatment; he or she may unknowingly communicate their beliefs to the patient, so biasing the result of the trial.

Where both patient and clinician are unaware of the nature of the nature of the treatment (drug versus placebo, for instance) the trial is referred to as double blind.  Where the clinician is unaware, but the patient is not, the trial is single blind.  A further important refinement, crucial where blinding of patient or clinician, is that the assessment is carried out an independent observer who is unaware of the treatment allocation.

10 Problems:

Yet the placebo controlled randomized double-blind approach does have its problems:

First, problems may arise because subjects randomized to different treatment groups may meet and discuss their treatment.  Assignment to natural groups (e.g. comparison to two schools or two geographical regions) may be preferable to randomization.

Second, blinding may not be feasible for some treatments.  While neither doctor nor patient may be able to distinguish a real tablet from a sugar pill, placebo tablet, there are no clear equivalents to placebo drugs for some treatments.

Third, participation in a study may affect the behaviour of people taking part.  Simply being monitored and assessed regularly may have a beneficial effect.

Fourth, participants agreeing to take part in a trial may not be typical of the general population of patients with that particular problem.  Entry criteria to a trial need to be strict to ensure comparability between groups and give the best chance of showing a treatment benefit.

Fifth, there may be a problem in the reduced compliance with treatment because of the possibility of receiving placebo treatment. If patients are told that they might be taking a placebo they might be more inclined to give up on the treatment if there are no immediate effects.

Sixth, using standard treatment in the trial may be artificial and have little relevance to the clinical practice. This may inhibit a more flexible patient-centred approach.  The trial may therefore not be a true test of the therapy as used in clinical practice and the needs of the patient may conflict with the requirements of research.

Seventh, individual variations in response are often ignored in an analysis that only considers average group responses.  Patients who are made worse by the treatment may not be given enough attention in the reports, unless they suffered particularly obvious side-effects.

Eighth, ethical problems may arise in a variety of contexts, particularly where placebo treatments are involved or the patient or clinician has a marked preference for one treatment option over another.

Ninth, the main outcome measure, based on clinical assessment and objective tests, may not reflect the patients’ perspective of what constitutes an important and beneficial change.  Patients may be more concerned with the quality of their lives, which may not be closely linked with changes in biochemical parameters or other disease indicators.

Tenth, the concern with eliminating the placebo effect when assessing a treatment in relation to a comparable placebo may mean that important psychological variables are neglected.  Therapist characteristics and the attitude of the patient to treatment are seldom examined in a medical context, and yet may be important determinants to the patient’s compliance with treatment and attitude toward illness.

The placebo effect has its equivalent in other parts of psychology. To a large extent the Hawthorne effect is a type of placebo effect. The Hawthorne effect occurs where a person’s behaviour a work (i.e change in productivity) is thought to be a function of some change in their circumstances (new office, greater pay) whereas what is having the effect is how they are treated differently.

There are those who are contemptuous of the placebo effect and those unscrupulous people who they claim manipulate others by cynically exploiting them. Others believe that it represents one of the most importance and effective ways to help people overcome problems.

About the Author

Adrian Furnham, Ph.D.

Adrian Furnham, Ph.D., is a professor of psychology at University College London and the Norwegian Business School.

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