Written by Karen Hovav, MD, FAAP | Reviewed by Katie E. Golden, MD
Key takeaways:
The nocebo effect occurs when negative beliefs about a treatment lead to a harmful effect. It’s the opposite of the placebo effect.
The nocebo effect can make interventions or treatments more painful and less effective. It can also lead to more side effects than originally expected.
People are more likely to experience the nocebo effect if they have anxiety, Type A personalities, and general fear of pain.
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You may have heard about the power of positive thinking. Scientists have known for decades that if a person believes that a medication or treatment will help them, that belief alone can lead to healing effects. This is the placebo effect. But negative thinking can be just as powerful. And come into play when a person believes that a treatment will be harmful. Here’s what the nocebo effect is, common examples, and what makes you more likely to experience the nocebo effect.
What is the nocebo effect?
The nocebo effect describes negative outcomes that can happen if someone believes something will cause them harm. For example, if you think a treatment will be painful, there’s a higher chance that you’ll experience pain. Even a belief about possible side effects can cause side effects from muscle spasms to chest pain.
The nocebo effect can lead to several negative effects, including:
Making treatments more painful
Making treatments less effective
Worsening symptoms
Causing more side effects
What’s the difference between the nocebo vs. placebo effect?
The placebo effect happens when a person experiences a benefit from their belief that a medication or treatment can be helpful. Researchers often see this effect in clinical studies. People with migraine headaches said they had significant pain relief after taking a placebo pill that was labeled as a real medicine for headaches. And it was as effective as when the actual medicine was labeled a placebo.
With the nocebo effect, people report side effects from the placebo treatment. One study found that 2 in 5 of those taking a placebo pill for migraines had side effects — like memory problems and loss of appetite. These still were reported even though participants were not given medicine.
What are common examples of the nocebo effect?
The nocebo effect can cause a wide variety of different symptoms. Common examples include:
Pain: This is one of the more common outcomes of the nocebo effect. For example, patients who were told that an epidural would feel “like a bee sting” had more pain than those reassured that they would be comfortable.
Muscle aches: People who take statins for cholesterol often report muscle aches as a side effect. But studies have shown rates of muscle aches are the same between participants taking a statin and those who are taking a sugar pill. This shows how the nocebo effect may cause the belief that statins cause muscle aches.
Sexual side effects: Patients who were told that beta-blockers could lead to sexual side effects were 3 to 4 times more likely to report this than the group not told.
Itching: People who expect to have itching with skin medications are more likely to actually have itching as a symptom.
Memory problems: In one study, people reported memory changes when they thought they might be taking an anticonvulsant with a side effect of memory difficulty.
Why does the nocebo effect happen?
There are several possible explanations for why the nocebo effect happens.
Sometimes it can happen from a process called conditioning. This is when a person learns to associate an environment with a response. For example, a person receiving chemotherapy might start to feel nauseated when they enter the chemotherapy clinic.
And when a person expects something negative, it can physiologically change how the body processes experiences. During the nocebo effect, it is thought that stress activates parts of the brain involved in processing pain. This activation then increases sensitivity to pain. It can also focus your attention on possible negative effects.
So the nocebo effect seems to be more common in people who:
Are more afraid of pain
Experience anxiety or depression
Have had a negative experience with the medicine or treatment in the past
Are told that the treatment will cause unwanted side effects or be painful
Have certain personality traits such as being pessimistic, neurotic, or Type A (highly competitive, focused on outcomes)
Researchers are still working on understanding exactly why the nocebo effect happens. And they’re looking to understand what parts of the brain are at work.
The bottom line
The nocebo effect is when harmful expectations can negatively affect a response to medication or treatment. Researchers are still learning more about how the nocebo effect can change feelings of pain, effectiveness, and side effects. Remember that the mind is a powerful force. So whether you believe that a treatment will be helpful or harmful, there’s a good chance your brain will prove you right.
References
Aslaksen, P. M., et al. (2015). Fear of pain potentiates nocebo hyperalgesia. Journal of Pain Research.
Blasini, M., et al. (2017). Nocebo and pain: An overview of the psychoneurobiological mechanisms. Pain Reports.
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