You’ve likely heard of the placebo effect, but you might be less familiar with its opposite, called the nocebo effect.

Placebos are medications or procedures that appear to be actual medical treatments but aren’t. A common example is the week of sugar pills that come in many monthly birth control packs.

The placebo effect occurs when a placebo actually makes you feel better or improves your symptoms.

The nocebo effect, on the other hand, happens when a placebo makes you feel worse.

Read on to learn more about the nocebo effect, including common examples and why it raises several ethical issues.

While there’s plenty of research about the placebo effect, the nocebo effect is still poorly understood.

But experts have identified a that seem to play a role in determining who experiences the nocebo effect.

These include:

  • how your healthcare provider talks about potential side effects and outcomes
  • your trust in your doctor
  • your past experiences with similar treatments
  • the of a treatment or medication

Experts are now looking at the nocebo effect to better understand how positive or negative thinking can impact a person’s physical health.

Imagine that you’ve been dealing with ongoing headaches. You make an appointment with a new healthcare provider. After hearing your symptoms, they decide to prescribe you a pill that you take every morning.

They warn you that the pill will cost a lot. They also tell you to expect certain side effects, including nausea and dizziness. What they don’t tell you is that the pill is made of sugar — that is, it’s a placebo.

You pick up your prescription and take the first pill. Within an hour, you feel the need to lie down. You feel the nausea coming on, and you could swear the room is starting to spin a bit. “The doctor warned me about this,” you think.

In reality, you’ve just taken a harmless sugar pill. But everything you heard during that appointment conditioned your brain and body to have a specific response.

Here’s a look at how the nocebo effect might play out in different health scenarios.

Migraine treatment

You experience a migraine attack at least twice a month. You used to take prescription medication to prevent them, but you haven’t been able to see your doctor since your prescription ran out.

With everything else going on, you don’t have time to make an appointment. Instead, you decide to order medication from an online pharmacy.

The last medication you took made you feel drowsy, so you do some research and choose a different, but similar, drug. You begin taking the medication.

After a few days, you begin to have trouble sleeping and notice your mood taking a dip. You remember that insomnia and depression were listed as possible side effects of the medication, so you stop taking the medication and decide to see a doctor.

The doctor takes a look at the medication and informs you that it’s just ibuprofen. But based on what your read (and likely some anxiety over ordering prescription medication online), you experienced side effects you wouldn’t have if you’d knowingly just taken ibuprofen.

Flu shot

You’re getting a flu shot for the first time. The nurse giving you the shot warns you that the larger needle size means the vaccine may hurt more than others you’ve received.

Though you’ve never had trouble getting shots in the past, you find this vaccination painful enough to bring tears to your eyes. The soreness persists for several days.

You might have a similar experience the next time you need a shot, even if it’s administered with a smaller needle.

Eczema creams

You have eczema on your arms that you’ve been treating with an over-the-counter (OTC) cream. But it doesn’t seem to be working. And you don’t like the way the cream stings when you apply it, a side effect the packaging warns about.

You decide to see your doctor to get a prescription for something else. They recommend a cream that should work very well without any side effects. After a few days of using the new cream, you notice your symptoms are clearing up.

As you’re applying the cream one day, you take a look at the active ingredients. Turns out they’re the same as those in the OTC product you tried without success. And the packaging mentions that you’ll likely feel a stinging sensation when you use it.

The only real difference between the two is how they were presented to you. You read that the OTC product would cause stinging before you even tried using it. But you started using the prescription version believing it wouldn’t have any side effects.

The nocebo effect raises several complex issues for healthcare professionals.

Informed consent

The policy of informed consent holds that you can’t fully consent to a procedure or treatment if you aren’t given all the information about it. In response, healthcare professionals work hard to ensure that they provide thorough, accurate information about treatments and medications.

But what if this information is playing into the nocebo effect, causing people to have negative side effects that they might not have otherwise?

In some cases, this might not be a huge deal. But in others, it can have a big impact on someone’s life.

For example, what if a treatment is potentially life-threatening? It’s important for the person to understand such a serious risk, but what if not telling them reduced the risk that it would actually be life-threatening?

Research

Even just researching the nocebo effect raises issues. Useful studies would require investigators to have people experience the nocebo effect.

This would mean intentionally causing people to experience negative side effects or outcomes, which is generally considered unethical when it comes to human studies.

Instead, experts will likely work to better understand the nocebo effect by examining the placebo effect more closely.

While the nocebo effect is often treated as a negative thing, it may be a key player in paving the way for better communication in healthcare settings.

For example, before administering a shot, a healthcare professional might say, “This may hurt a bit.” But what if they just said, “Most people feel no pain at all”? Even adding a simple “only” to the statistic “10 percent of people taking this drug had side effects” may help.

It may also help to shed more light on the mind-body connection and how your mindset can influence your physical health.

The placebo effect demonstrates how positive thinking can improve treatment outcomes. The nocebo effect suggests that negative thinking may have the opposite effect.

Experts still aren’t totally sure how the nocebo effect works, but your relationship with your healthcare provider and their communication style likely play a large role.