The Nocebo Effect

He still wanted the purple pills.

He was adamant they worked far better than the cheaper, non-purple generic alternative. The pills were chemically identical in terms of the active drug, but the non-branded ones, he told me, just didn’t work at all.

Most people are already aware of the phenomenon called the placebo effect. The word placebo is from the Latin “I shall please,” and describes the effect where a patient’s condition is improved by something fake or relatively inert.

The placebo effect is subjective, but that’s not to say it doesn’t have a real effect. Just like the example of the purple pills that happened with a real patient of mine, some studies have shown that large pills work better than small pills, coloured pills work better than white pills, and even injections and surgery are subjectively more powerful on a patient’s outcome than just a pill.

There’s a fair amount of medication that we use today where you could statistically attribute a meaningful part of its overall effect, how well it works, to the placebo effect rather than to the drug itself alone.

I don’t really want to talk about the placebo effect. What I really want to talk about is the counterpart of the placebo effect, called the nocebo effect.

Nocebo is taken from the Latin “I shall harm,” and describes the subjective negative effects of a treatment. I’ve seen many examples of the nocebo effect over the years, particularly how treatments given to a patient in a certain way, even by clinicians, can negate their overall effect and even cause unwanted side effects. I’ve also seen how the patient’s own mental attitudes and beliefs can cause the nocebo effect, and how this affects their health and wellbeing in the long term.

I have no doubt that some medications cause unwanted side effects. Yet there’s also evidence from research papers that confirms that even telling a patient about a common side effect makes them statistically more likely to get that side effect.

Patients need to make their own informed decisions about whether to take or not to take a medication. However, the nocebo effect doesn’t really help the patient get the true benefit of the treatment they’re being prescribed.

I got a call from a patient a few days ago before I originally wrote this lesson. He’d just read the product information leaflet inside the pill packet, and he was convinced he was already getting most of the side effects listed, from the reasonably inert drug I’d prescribed him. Only just a few days into his treatment course, he also went on to tell me that even before he started the medication, after he’d read the leaflet, he realised he’d already been getting most of the other side effects on the leaflet too.

The nocebo effect doesn’t always cause side effects. Sometimes the nocebo effect is just when the beneficial effect of a treatment is negated. What I’ve found out is that what a patient believes plays a real role in how effective and how ineffective a treatment or a drug feels to them.

Let’s take this a step further. Imagine someone sitting in their room, fed up, convincing themselves they’re never going to get better, dwelling on their problems, their pain, how their treatment will never work. They’re mentally doing their best to negate the effect of the treatment they’re receiving. That’s in addition to the derogatory effect that sitting in a room feeling sorry for yourself will generally have on your mental wellbeing.

Doctors can also make a huge difference in how they deliver treatments. Some are often unaware of how the nocebo effect, the use of poor language, the negative framing of comments, can affect their patients’ outcomes.

I’ve seen patients given a poor prognosis lose all quality of life in the time they had left, stopping doing anything that brought them joy because they’d already given up on all of it. I’ve also seen patients handed a similarly difficult prognosis who kept doing the things that mattered to them for as long as they possibly could, right until the end. I want to be honest with you about what the evidence actually shows here, because this is an area where it’s easy to overstate the case: a positive mindset doesn’t appear to change how long a serious illness allows someone, the research on that is fairly clear, and I’d never want a patient or their family blaming themselves or a loved one for “not fighting hard enough” when an illness takes its course. What mindset does seem to change, enormously, is what that time is actually like to live through.

A physician who’s mindful of this, who promotes the placebo effect and minimises the nocebo effect through how they communicate, really can shift how well a treatment works and how a patient experiences it. It’s a real, measurable effect, even if it resists being reduced to a single tidy percentage.

Too often, however, the side effect of a treatment is that if a patient feels better, then they also have to get on with their life. Maybe for some, this is a side effect they’d rather live without.

There’s not always a medical cure that works for every problem, but when there is, I know it works a lot better if the patient works at what they need to do to get themselves better too.

Getting back to the example at the beginning, in the end I gave the patient the purple pills he wanted on a private prescription. The fact that he paid more money for them may even have helped his overall perception of their (and his) potency.

The fact is, negative beliefs and thoughts, be they conscious or unconscious, can affect your health. Our immune, hormonal, and endocrine systems appear to respond, at least in part, to our overall mindset. This is the point I’m really trying to get across in this lesson.

If you think something will work, or if you think something won’t work, you have some ability to move the odds in either direction.

Some conditions start as symptoms and feelings with, at first, no clear physical marker that shows up on a scan or a blood test. In some of these, a nervous system that’s become highly sensitised, essentially turning up its own alarm signal, plays a real part. This process is called central sensitisation, and it’s a genuine neurological phenomenon, not a sign that a person’s pain or fatigue isn’t real.

Conditions like ME/CFS (chronic fatigue syndrome) and fibromyalgia are a good example of how complicated this all gets, and I want to be careful here, because these are genuinely difficult, and at times contested, areas of medicine, not simply psychological illness dressed up in physical symptoms. The fatigue and pain are real and physical. For some patients, psychological support alongside careful pacing and the right physical care can be part of what helps them gradually do more of what matters to them. For others, progress is much slower and harder won, whatever support is on offer, and that isn’t a failure of willpower or a choice they’re making. Current UK guidance has moved away from framing these conditions as something to be cured through mindset or exercise alone, and quite rightly so.

Most people are doing this course to help the way they think. Yet some have been directed to this course because they have physical conditions which have a mental or emotional component alongside the physical one. The mind and the body are connected in many different ways. Better mental health is generally associated with better overall wellbeing. How you think and what you say to yourself is part of that picture, without being the whole of it.

I had a patient, call her Michelle, who came in with chronic pain. She’d had every test, every scan, every specialist opinion. Nothing that fully explained the severity of the pain she was in. But the pain was real. She felt it every day. It limited her life. She’d stopped working, stopped socialising, stopped doing anything that might make it worse.

“Do you think it’ll ever get better?” I asked her.

“No,” she said immediately. “I’ve had it too long now. It’s just who I am.”

“What if you’re wrong?”

She looked at me like I’d suggested the earth was flat.

Six months later, after working with a pain psychologist, alongside her physical treatment, she was back at work part-time. The pain hadn’t completely gone, but it no longer controlled her life to the same extent. What changed wasn’t just her body. It was also her beliefs about her body, and what she felt able to do despite the pain.

That’s the nocebo effect easing off, or perhaps it’s better described as removing some of the psychological weight that was making a difficult physical picture even harder to live with.

So if you think something will work, or if you think something won’t work, you have some ability to move the odds in either direction. Your beliefs matter. Your expectations matter. Your internal dialogue matters. None of that means beliefs alone determine every medical outcome, but they’re a genuine part of the picture, and one worth paying attention to.

You’re not powerless over your health. You’re not a passive recipient of whatever your body decides to do. Your mind is part of the system. It’s not separate from your physical health. It’s connected to it.

So pay attention to what you’re telling yourself about your health, your treatment, your capabilities. It’s one part of a much bigger picture, but it’s a part that’s genuinely within your control.

Further reading

• Benedetti, F. (2008). Placebo Effects: Understanding the Mechanisms in Health and Disease. Oxford University Press.
• Barsky, A. J., Saintfort, R., Rogers, M. P., & Borus, J. F. (2002). Nonspecific medication side effects and the nocebo phenomenon. JAMA, 287(5), 622-627.
• Colloca, L., & Miller, F. G. (2011). The nocebo effect and its relevance for clinical practice. Psychosomatic Medicine, 73(7), 598-603.
• Moseley, G. L., & Butler, D. S. (2015). Fifteen years of explaining pain: The past, present, and future. Journal of Pain, 16(9), 807-813.
• Häuser, W., Hansen, E., & Enck, P. (2012). Nocebo phenomena in medicine: Their relevance in everyday clinical practice. Deutsches Ärzteblatt International, 109(26), 459-465.