What is the placebo effect?

What are placebo effects? A proposed framework for understanding the issue of placebo effects.

by John Jackson © 2005

The placebo effect is the phenomenon whereby a patient's symptoms can be alleviated by an otherwise ineffective treatment; most likely because the individual expects or believes that the treatment will work. The placebo effect is actually a generic term for various effects that cause people to reinterpret their illness or symptoms.

The placebo effect is a psychological response to treatment. Physical conditions do not improve with placebos. Placebos do not cure, as many people mistakenly believe; it is the perceived improvement of symptoms that characterizes the placebo effect.

It should be noted that all medicines induce the placebo effect. It is only those treatments that have an effect above and beyond that produced by a placebo that are classed as efficacious.

What causes the placebo effect?

It is still not fully understood exactly what causes the placebo effect, although the patient's beliefs and expectations may invoke a "conditioned response" (as in Pavlov's dogs). We are conditioned to believe that medicine makes us better when we're ill, so any treatment that we receive may make us psychologically confirm this belief.

Research has also found that this conditioned response stimulates the release of endorphins in the brain. Endorphins prevent pain and invoke a feeling of euphoria by binding to certain receptors in the brain. Endorphins are the body's own morphine-like painkillers. Their effect is a short-term one however, so the role of endorphins in pain relief and overall placebo effects is probably quite small.

The positive outlook of the doctor combined with the patient's faith in the treatment may also lead to a lessening of stress and anxiety in the patient. Stress and anxiety adversely affect the body and increase patients' focus on symptoms. Reduction of stress and anxiety may subsequently reduce some physical symptoms, as a secondary effect, that are exacerbated by stress and anxiety.

It is interesting to note that doctors researching the placebo effect have noticed that large dummy (placebo) pills are more effective than small ones, and coloured ones are more effective than white; showing that the expectation of the strength of the pill affects patients' responses.

Is there a downside?

  1. The "Nocebo" effect is the phenomenon where people perceive symptoms or side effects from an ineffective treatment because they have been led to believe they might occur, although this is usually only noticed during clinical trials where medicines have to be compared to placebos to test their true effectiveness.

  2. Placebo responses, such as feeling less pain or more energy, do NOT affect the actual course of the disease. Thus placebo responses can obscure real disease, which can lead to delay in obtaining appropriate diagnosis or treatment.

  3. The placebo effect can give the illusion that bogus remedies have worked. This can convince people that they are suffering from a build up of "toxins", food intolerance, or non-existent "allergies"; the very sort of conditions that alternative practitioners focus on.

    This can lead to the perpetuation of the use of ineffective and irrational medicinal therapeutic procedures, such as those used in alternative medicine.


The placebo effect is a real and powerful psychological response. It tends to be thought of as a response to a bogus treatment, but it is actually present in all treatments. It is generally a beneficial response, although due to the nature of its feel-good factor it is possible that symptoms of a serious illness could be masked by it when using a bogus treatment or therapy.