Nocebo Effect, What Is it and How Does it Work?

Surely you know the placebo effect, but do you know what the nocebo effect is? Here we tell you!
Nocebo Effect, What Is it and How Does it Work?
Leticia Aguilar Iborra

Written and verified by la psicóloga Leticia Aguilar Iborra.

Last update: 23 April, 2021

Although the characteristic phenomenon of the placebo effect is known, the nocebo effect is also related to the administration of treatments and the possible effects, in this case adverse ones.

The nocebo effect, in general terms, is similar to the placebo effect in that the adverse effects of any substance, medicine, or some other type of treatment appear subjectively.

In this sense, in the nocebo effect, the beliefs and expectations of the individuals influence the result of the treatments, although these differ from properties that imply some type of reaction in the body.

Defining the nocebo effect

The nocebo effect is common one.
This effect is relatively common.

The term nocebo, comes from Latin, which could be translated as “to do harm”. Walter. P. Kennedy was the pioneer in referring to this phenomenon in 1961 to refer to the harmful effects administered after a placebo treatment.

In this sense, the nocebo effect refers to the appearance of adverse effects after the administration of any type of treatment. These adverse effects appear subjectively, when the administration of any type of substance is harmless for the organism.

The nocebo effect is often detrimental to some of the research carried out for treatment purposes, as it may alter the research results. Therefore, it’s extremely necessary to develop positive framing strategies.

In this way, the patient is provided with information about the treatment that’s being administered, and the possible adverse effects in order for them not to create negative expectations in the individual that may lead to the nocebo effect.

These effects treat most non-serious symptoms. They appear independently to the administration of the dose and aren’t attributable to the treatment.

What causes it?

Experts still don’t know the clear mechanisms by which the nocebo effect occurs. In some cases, investigating this type of phenomenon may involve ethical and/or legal problems. The latter means that the veracity of the symptoms isn’t mentioned to the individual and they aren’t informed about the possibility of adverse symptoms, if any.

However, we do know about some factors that can contribute to the nocebo effect to a greater or lesser extent. Among them, the following can be found.

Factors that contribute to the appearance of the nocebo effect

Psychological mechanisms are the phenomenon of classical conditioning. They occur as a result of the relationship of contingencies with discriminative stimuli that facilitate an adapted response, depending on the individual’s expectations.

The memory of a negative response to a type of drug, or to the experience of the effects produced with a similar drug or other type of treatment in other people, influences the response of the nocebo effect.

In this sense, the recommendation of the treatment, and clear and concise information on the effects of the treatment is essential in order to prevent the appearance of this phenomenon.

Personality factors also stand out, since some traits can affect the appearance of the nocebo effect. Today, we know that introversion traits or a tendency to pessimism can influence the appearance of this effect. The same can be said in individuals with neurotic features, who are prone to worry.

Neurobiological mechanisms appear to be triggered by the anticipatory anxiety response triggered by negative suggestions. The activation of the cholecystokinin receptors (CCK) and the hyperactivation of the hypothalamic-pituitary-adrenal (HHA) axis facilitate the response to pain, producing hyperalgesia.

Contextual factors such as the socio-cultural environment and the specialist-patient relationship are other elements of great importance. Clear information, where the positive aspects of the treatment are reflected, as well as warning about the negative ones, can mediate the risk of the appearance of the nocebo effect.

Clinical consequences

The clinical consequences of the nocebo effect influence therapeutic and research results, although more research is needed to specifically get to know the cause of them. However, its influence is undoubted in the follow-up of treatment prescriptions.

Therefore, therapeutic prescriptions are influenced by the nocebo effect. It has been seen that some pathologies such as Parkinson’s, multiple sclerosis, neuropathic pain, or migraine are affected by the phenomenon of the nocebo effect.

Also, some treatments are more likely to be involved in this phenomenon. This is the case of statins associated with muscle pain, antiepileptic drugs associated with neurological syndromes, or finasteride, associated with erectile dysfunction.

How to prevent such an effect?

The nocebo effect can be prevented.
A correct doctor-patient relationship can help with this problem.

Clear and concise information from professionals is essential in order to reduce the risk of the nocebo effect. Information that isn’t misleading, and yet, at the same time, reassuring.

Positive framing tends to focus attention on the benefits of treatment in order to prevent negative expectations about it that have already arisen in the individual.

The latter includes searching for the treatment and its effects on the internet, fake news in the media, observing the effects of the treatment on other people, etc.

In other words, the professional’s ability to inform the patient about the treatment is a decisive factor. Although one of the causes of the appearance of the placebo effect is related to the relationship between the professional and the patient, the nocebo effect is also related to the same relationship.

Other strategies can be informed consent and non-information, depending on what the individual wants to know. There’s also the possibility of talking about the nocebo effect clearly to individuals to create awareness of the possibility this may arise during the treatment process.

However, the appearance of certain symptoms is usually inevitable. Emphasis should be placed on the ability of patients to correctly address mild symptoms and make them aware that intolerance is a problem that can be resolved through adjustments in treatment.

  • Ferreres,J., Eladi – Baños, J. & Farré M.(2004). Efecto nocebo: la otra cara del placebo. Medicina Clínica, 122 (13), 511-516.

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