What is the placebo effect?

A placebo is a medical treatment or technique intended to deceive a clinical experiment participant. It contains no active ingredients but still often produces a physical effect on the individual.

Placebos are essential for constructing reliable clinical trials. Many experiments have been focussed on their once-surprising impact on participants.

The placebo effect refers to an individual being affected by a placebo. Even inactive treatment has shown repeatedly a measurable, positive response to the health. The placebo effect’s effectiveness is considered a psychological phenomenon.

Important facts about placebos

  1. The placebo effect has been measured in thousands of medical experiments, and many doctors admit to regularly prescribing placebos.
  2. Drug companies must show that their new drugs work better than a placebo before the drugs are approved.
  3. Placebos have been shown to affect a range of health conditions.
  4. The color of a tablet can alter the strength of its placebo effect, and larger pills induce a stronger effect than smaller pills.
  5. Some believe the self-healing properties of the placebo effect can be explained by evolutionary biology.

What is the placebo effect?

Placebo medications
Placebo medications contain no active ingredients but if the participant thinks they are taking medicines, a placebo can improve their physical condition.

The placebo effect explains any psychological or physical impact a placebo therapy has on a individual.

Placebo is an integral part in all successful clinical trials.

In early clinical trials a new drug ‘s capabilities were evaluated against a group of people who did not take any medication. However, after discovering that the simple act of taking an empty tablet can generate the placebo effect, having a third group of participants is now deemed essential.

This additional group takes a tablet that does not contain any active ingredient to calculate the answer to them. For example, participants in that group will take a sugar pill.

A medication is licensed only when it has a greater effect than a placebo.

It has been shown that placebos produce measurable, physiological changes, such as increased heart rate or blood pressure. However, placebos, such as depression , anxiety, irritable bowel syndrome ( IBS), and chronic pain, are most strongly influenced by illnesses that rely on self-reporting symptoms for measurement.

The strength of placebo interventions varies according to many factors. For example, an injection causes a stronger placebo effect compared to a tablet. Two tablets work better than one, capsules are stronger than tablets and larger pills are more reactive.

One analysis of several studies showed that even pill color made a difference in placebo outcomes.

“Red, yellow, and orange are associated with a stimulant effect, while blue and green are related to a tranquilizing effect.”

Dr. A. J. de Craen, researcher, BMJ.

Researchers have shown repeatedly that treatments like “sham” acupuncture are just as effective as acupuncture. Sham acupuncture uses needles which are retractable and do not pierce the skin.

Placebos may reduce the symptoms of several conditions, including Parkinson’s disease, depression, anxiety , and fatigue.

The placebo effect varies among cultures, too. The placebo effect is low in Brazil when it comes to treating gastric ulcers, higher in northern Europe and particularly high in Germany. For Germany, however, the placebo effect on hypertension is smaller than elsewhere.

How does it work?

The placebo effect differs differently, and its intensity varies from disease to disease. The explanations for a placebo ‘s power are not completely understood. Given the variability in response, more than one mechanism is likely at work.

Below are four of the variables that were believed to be part of the placebo effect.

1. Expectation and conditioning

Part of the placebo ‘s strength lies in the individual’s assumptions about taking them. Such requirements can be linked to the diagnosis, the drug or the doctor prescribing.

This expectation can cause a drop in or recategorize the stress hormones. For example, a “sharp pain” may be interpreted as a “uncomfortable tingling,” instead.

On the other hand, if the patient does not expect the medication to function, or expect side effects to occur, the placebo will produce negative results. In these cases, instead, placebo is considered a nocebo.

In one study , participants who had recently taken genuine opioids were given placebo opioids. Respiratory depression is a well-documented side effect of the opioids. The researchers found that , despite having no active ingredients, the placebo drug elicited respiratory depression.

Some think classical conditioning might play a part in the placebo effect. People are used to taking and feeling better with the drug. Taking a drug provokes a positive response.

Conditioning and expectation are separate mechanisms, but are likely to be associated with them.

2. The placebo effect and the brain

Studies in brain imaging have found measurable changes in the neural activity of people suffering from placebo analgesia. Parts of the brain stem, spinal cord, nucleus accumbens, and amygdala were involved.

Strong placebo responses were also related to increased activation of the dopamine and opioid receptors. Both of these chemicals participate in brain reward and motivation pathways. In contrast, nocebos have been found to reduce the activity of the dopamine and opioid receptors.

Any of these neural changes arise in areas of the brain where antidepressant medications are frequently targeted. This might account for the 50 to 75 percent placebo response rate in antidepressant trials.


Psychoneuroimmunology is a relatively new area of research. It studies the direct effect upon the immune system of brain activity. Much as a dog may be conditioned to salivate at the sound of a bell, so when faced with a particular stimulus mice may be conditioned to suppress their immune system.

A positive outlook has long been known to help stave off illness. That pseudo-science has become a fact of science in recent years. Expecting health changes can affect the effectiveness of an individual’s immune system.

The pathways by which the immune system is affecting the brain are complex. It was only recently that an theory started to develop. There is a possibility that this type of interaction plays a role in the placebo effect.

4. Evolved health regulation

A mammal ‘s body has developed valuable physiological responses to pathogens.

For example, fever helps elevate internal temperature to remove bacteria and viruses. However, because such responses come at a cost, the brain determines when a specific response should be carried out.

For example, the body does not conduct the fever response to infection in late pregnancy or during malnutrition states. An elevated temperature could damage a infant, or use more energy than a hungry person could spare.

The evolved theory of health regulation suggests that a strong belief in a medication or therapy may relieve the symptoms. The brain “decides” it does not need to mount the appropriate response, such as fever or pain.


At one time, placebos had only been used as a control in experiments. However, they have now been extensively studied as a treatment in their own right, due to their ability to make changes to the body.

The following conditions proved positive reactions to the placebo effect:


The power of a placebo to relieve pain is called placebo analgesia. It is assumed to function in one of two ways. Either placebo initiates the release of natural painkillers called endorphins, or they alter the perception of the pain by the individual.

Moreover, genuine analgesics have been shown to be more successful if a person understands that the medication is being delivered, rather than the medication being delivered without the knowledge of the person. In this situation, the placebo effect can be seen as a aid for legitimate intervention.


It is assumed that the efficacy of antidepressants is mainly dependent on the placebo effect. One review of eight studies found that placebo antidepressants had been successful over a 12-week period , showing the possible long-lasting impact of placebos.

Anxiety disorders

The placebo effect is especially prevalent in anti-anxiety drug trials and substantially interrupts the discovery and testing of new forms of medication.


A review of cough medication studies found that “85 percent of cough reduction is related to placebo treatment, and only 15 percent is attributed to the active ingredient.”

Erectile dysfunction

People with erectile dysfunction responded well to placebo treatment.
People with erectile dysfunction responded well to placebo treatment.

Participants were split into three classes, in one study. The first group was told they would receive an erectile dysfunction treatment, the second group was told they would receive either a placebo or an actual remedy, and they told the third group they would receive a placebo.

In addition, all three groups were given placebo starch tablets, but the erectile dysfunction improved significantly in all three groups without any variations between the three groups.


A meta-analysis showed that placebo response ranged from 16.0 percent to 71.4 percent in people with IBS. It was also observed that in trials where participants are expected to take medication less often, the placebo effect is stronger and individuals with lower rates of anxiety tend to be more prone to the placebo effect.

The placebo effect was enhanced with a more attentive attitude from clinicians.

Another study showed that their IBS symptoms improved even when the participants were aware they were taking a placebo.

Parkinson’s disease

A analysis of 11 clinical trials showed that 16 percent of patients with Parkinson’s disease showed significant improvements in placebo groups, often lasting for 6 months.

The effect seems to be in part due to the release of dopamine in the striatum.


Participants in drug trials of anti-epilepsy have a placebo response of 0 to 19 percent. For this trial a “placebo response” was described as a 50 percent decrease in their normal frequency of seizures.

Uses of placebos

Doctors around the world are using placebo for medicinal purposes because of its effects on a range of illnesses. A Danish study in 2008 found that in the past year, 48 per cent of physicians had prescribed placebos at least 10 times. These placebos were most usually antibiotics for viral illness, and fatigue vitamins.

A similar survey of Israel’s doctors found that 60 percent had prescribed placebos to prevent patients who wanted unjustified treatment, or “needed to relax.”

Is it ethical?

That usage poses ethical questions. The physician misleads the patient. On the other hand, if placebo has the desired effect, then successful treatment should still be considered.

Another claim suggests that the right diagnosis of a severe ailment can be delayed by using a placebo to placate a patient. Potentially doctors and pharmacists may open themselves up to charges of fraud.

There are more ethically sound uses of placebos in medical practice, but debates for and against the use of placebos are likely to continue for quite some time, like any other ethical debate.

Placebos, for example, can be effective in treating certain burn victims. Due to the associated respiratory depression opioid pain relief can not always be used. A saline injection given under the guise of a powerful painkiller can reduce the distress of a patient in this case.

Harnessing the power of the placebo

Instead of ignoring or trying to mitigate placebo effects, current and future researchers are finding ways of harnessing and exploiting placebo ‘s strength beneficially.

In a variety of cases placebos have been shown to be efficient. These can potentially improve medical conditions if they can be used alongside therapeutic therapies.

Clinical oncologist and medical professor Robert Buckman concludes that:

“Placebos are extraordinary drugs. These tend to have some effect on almost every symptom known to mankind, and work in at least a third of patients and often up to 60%. These have no significant side effects and are not used in overdose. In short, they hold the prize in the world’s pharmacopeia for the most adaptable, protean, effective, safe, and cheap drugs.

The placebo effect ‘s power opens up an exciting opportunity for new avenues to explore.

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