Autumn has arrived, painting the landscape with the golden hues of falling birch leaves. I find myself at my desk, contemplating the screen of my laptop.

Today marks a significant step forward. Since receiving my diagnosis, I finally mustered the courage to type the name of my cancer alongside the word ‘prognosis’ into a search engine. Now, I face the dilemma of whether or not to press the return key.

This moment feels like a crossroads, presenting me with two distinct paths. In one scenario, I choose not to press the button, opting for ignorance, believing that what I don’t know can’t harm me. In the other, I decide to face reality, pressing the return key, diving into the depths of information about my condition, and seeing where this knowledge leads me.

Back in February 2020, surgeons removed the cancer, yet uncertainty lingered regarding its exact nature. Biopsy samples offered some clues, and a month later, during a meeting with my oncologist, I finally learned its name.

In my profession, I regularly engage with experts and navigate through complex jargon. With a background in psychology, a PhD in neuroscience, and a career as a scientist, my work involved deciphering the brain’s intricate workings and linking neural activity to disease. For the past two decades, I have also been dedicated to science writing, exploring and explaining the world of research and discovery.

In my job I am used to grilling experts and deciphering complex terminology. I have studied psychology. I have a PhD in neuroscience. I have worked as a scientist, probing the intricate workings of the brain, trying to unravel the connections that link neural activity with disease. I have also spent the past 20 years working as a science writer.

But in that moment with my oncologist, I was a scared, tongue-tied patient. The result was that, although I came away with a plan for my near future, I knew very little of my long-term prognosis.

I didn’t ask and my oncologist didn’t say. And so it remains to this day. Although I’ve since had plenty of hospital appointments, something always stops me from asking about it.

Why? Well, around 15 years ago, I interviewed an American doctor, Clifton Meador, and had never forgotten the story he told me about a patient diagnosed with late oesophageal cancer who was given just a few months to live. A few months later he died.

This part of the story is sad, if unremarkable. But it doesn’t stop there. After this patient’s death, an autopsy showed there was no evidence of the widespread cancer that was supposed to have consumed him. It appeared there had been an administrative error – the patient was accidentally given someone else’s diagnosis.

Clifton Meador told me this man’s death was caused by something called ‘the nocebo effect’.

In Latin, the word nocebo means ‘I will harm’. You’ve probably heard of the similar-sounding placebo effect – which occurs when someone takes a sugar pill, and then feels better as a result. Positive expectations lead to positive health outcomes.

The nocebo effect is the placebo effect’s evil twin; it’s when people taking placebos are warned about side-effects of the drug (they’re not taking) and go on to develop them. But it’s also much bigger and broader than this.

The nocebo effect can conjure blindness and paralysis, seizures, vomiting and asthma attacks. With no brain injury in sight, it can trigger the symptoms of concussion. With no allergen present, it can induce features of an allergic reaction – watery eyes, runny nose and an itchy rash.

When cancer patients experience nausea sometimes even days before they have their chemotherapy, it is not the toxic drug that is to blame – but rather the nocebo effect.

It affects many of those who believe they have intolerances to certain ingredients, such as lactose or gluten. Research shows that, when self-reported ‘gluten-intolerant’ people are given gluten-free bread but told the bread contains gluten, very often they develop symptoms after eating it – and when some gluten-intolerant people are covertly fed regular bread but told it’s gluten-free, they don’t get symptoms.

The nocebo effect helps to explain why people with back pain can have the same amount of physical damage but wildly different degrees of disability. And why the decline of patients with cancer and other chronic conditions sometimes has less to do with the actual course of their illness, and more to do with their expectations of it.

If this all sounds like the sort of thing that happens to other people, think again.

If you ever felt lousy after having the Covid-19 vaccine, there’s a very good chance that your symptoms were caused not by the vaccine, but by the nocebo effect.

If you’ve ever developed side-effects to a prescription medication, there’s a reasonable chance the phenomenon was responsible for at least part of your suffering.

Now, in a new book, I’ve tried to make sense of the hidden impact of the nocebo effect – and to show how challenging our thoughts and expectations could reap positive change for our health.

During my research I have pored over hundreds of academic papers and interviewed dozens of experts, among them Ellen Langer, a professor of psychology at Harvard University, one of the pioneers in this field.

Professor Langer, who has more than 200 peer-reviewed studies to her name, has shown time and again that thoughts and beliefs can be powerful entities. In one of her most recent studies, people with type 2 diabetes were given milkshakes labelled as ‘high sugar’ or ‘low sugar’ but, unbeknown to them, the drinks were identical.

Yet their blood glucose levels increased more after drinking the ‘high-sugar’ milkshake than after the ‘low-sugar’ one. Their expectations of what was in their drink altered their metabolism more than the actual ingredients.

In another key study Professor Langer co-authored, hotel chambermaids who were persuaded to believe that cleaning was good exercise lost a kilogram in weight in a month, despite not changing their behaviour. Their blood pressure and BMI dropped, too.

When I studied neuroscience, we were taught that discrete parts of the brain control discrete aspects of experience, such as movement or fear. Today, we realise that the same parts of the brain that influence bodily processes also influence psychological states. Mind and body aren’t separate entities.

This ‘mind-body unity’ as Professor Langer calls it, is central to both the nocebo and placebo effect.

The power of the nocebo on ageing is reflected in the findings of The Baltimore Longitudinal Study of Aging, America’s longest-running scientific study of human ageing.

Back in 1968, researchers asked participants – then in their 30s – about their attitudes to old age.

Thirty-eight years later, while many had had brushes with ill health, those who’d held negative age stereotypes when young were twice as likely to have since suffered from cardiac problems, such as heart attacks, stroke and angina.

One group of participants had undergone brain scans, which showed that over a ten-year period, the hippocampus (key to memory formation and retention) had shrunk.

This happens with age, but work by Becca Levy (a professor at the Yale School of Public Health, who’s published more than 140 articles on ageism) showed that the rate of shrinking in those who held negative age beliefs was three times greater than in those with positive age beliefs.

And people who have negative age stereotypes early in life experience about 30 per cent greater memory decline as they age than those who have positive age stereotypes.

There are numerous factors that can increase the chances of developing Alzheimer’s, including things we can’t change, such as age and genetics – and things we can change, such as smoking and obesity.

On their own, none are enough to cause the disease, but they do all subtly tip the odds. Negative age stereotypes also tip the odds, so it’s time we recognised these beliefs for what they are: a modifiable risk factor for neurodegeneration.

The way we think about ageing can also affect how long we live.

In the Ohio Longitudinal Study on Aging and Retirement, people in the US town of Oxford over the age of 50 were asked their thoughts on ageing – over 25 years later, in 2002, when Professor Levy tallied their responses with data from the US registry of deaths, those who’d recorded a positive view of ageing lived on for a further 22.5 years, compared with 15 years for those with a negative view.

In other words, a negative attitude to ageing stole 7.5 years of life.

Hundreds of studies from all over the globe have now reiterated the same important message. If you believe that old age is a time of frailty and decline, it’s more likely to become so.

There are a number of potential mechanisms for this, but the DNA inside our cells is key.

This is organised into long, straggly units called chromosomes – the ends of these are tipped with protective structures called telomeres, which act like the plastic tips of shoelaces that prevent fraying. Every time a cell divides, a little bit of the telomere wears away.

Over weeks, months and years, the telomeres get progressively shorter until the cell just can’t carry on. It either commits suicide, or it becomes pro-inflammatory and starts to cause health problems – many of today’s biggest killers, including cardiovascular disease, diabetes, Alzheimer’s and a number of cancers, have an inflammatory component.

Age is known to speed the erosion of telomeres – an enzyme called telomerase helps to rebuild the telomeres, but older cells have less of it.

Stress is another factor: telomerase works less well in cortisol-soaked cells. Negative expectations are a third factor. Professor Levy has shown that people with negative age stereotypes have shorter telomeres, and the more doom-laden their predictions, the tinier the telomeres get.

The older we get, the more likely we are to develop cancer, too, so now it’s time to ask the big one. Can our thoughts influence it?

I think most scientists would agree that stress doesn’t cause cancer. The vast majority of all cancers are caused by a fault or ‘mutation’ in the genetic code.

But cancer cells are hardy little blighters. They’re very good at not dying. Animal and cell-based studies have shown that stress can help cancer cells to survive and spread. And when stress hormones interact with immune cells, it can reawaken dormant cancer cells.

Studies of human cancer patients are conflicting, so I speak to Asya Rolls. She works at the Technion – Israel Institute of Technology in Haifa, Israel – where she leads a team dedicated to exploring the effects of the brain on the immune system and physical health.

Her team has shown that nerve cells (neurons) in the ventral tegmental area (VTA) – a part of the brain known to play a role in positive emotion and reward processing – communicate with the bone marrow, where most immune cells are made.

When these neurons are activated, the brain talks directly to the source of the immune system. In mice studies this has been shown to rein in cancer and, more recently, to help speed recovery after heart attacks.

Rolls’ work suggests that processes in the brain can have a dramatic effect on disease in the body, but her biggest fear is that her work will be misinterpreted. She worries that people with cancer will either stop taking their treatment because they think positive thinking can save them, or blame themselves for their disease because they didn’t think positively enough.

‘Thinking negatively doesn’t give you cancer. Thinking positively won’t cure it,’ she tells me.

I agree, and yet there’s something more here.

Clinically proven cancer therapies should always be the first-line treatment – but if there’s even the slightest chance that the placebo effect could help, surely it has to be worth investigating? To this end, Rolls is researching non-invasive ways to activate these neurons in people. Watch this space.

Meanwhile, another autumn has come around and I’m here again. I have typed the name of my cancer and the word ‘prognosis’ into the search engine. Only now, I feel better placed to decide whether to hit the return key.

I keep coming back to the research of Asya Rolls and how, in mice at least, specific patterns of neural activity can affect the way cancer behaves.

I’m feeling positive about my future. I don’t need to know everything. So for now, I choose masterfully to ignore my cancer and get on with the rest of my life. I place my trust in the healthcare system and the doctors who care for me.

I choose to participate actively in the things that bring me joy: my family and friends, the natural world around me, biscuits, books – and my dog. They help to keep me well. As much as I can, I opt to create a story for myself that is fuelled by expectations that are helpful, not harmful.

• Adapted from This Book May Cause Side Effects by Helen Pilcher (Atlantic Books, £22), published on May 7. © Helen Pilcher 2026.
• To order a copy for £19.80 (offer valid until May 9, 2026; UK P&P free on orders over £25) go to mailshop.co.uk/books or call 020 3176 2937.

Is this why flu jabs and statins make you feel poorly? 

I’m sitting in the car at the local Covid-19 vaccination centre with my 14-year-old twins, writes Helen Pilcher.

It’s 2021 and, in the UK, kids have yet to be offered routine vaccination – but with vulnerable adults in the family, mine get to jump the queue.

None of their friends have been vaccinated and their social media feeds have been seeding their brains with anxiety and mixed messages, so it’s taken a lot of reassurance to get them here.

As we wait, a lady with a clipboard approaches and speaks directly to the children. ‘It’s just a tiny scratch. You’ll hardly feel a thing. Let me just run you through the possible side-effects.’

Before I can interject, she is already halfway down her list. ‘Pain at injection site, tiredness, headache, chills, fever, joint pain, nausea, vomiting, generally feeling unwell.’

I’m trying to interrupt, but she is unstoppable; a Terminator of doom-laden prophecies. ‘Very rarely, people can develop an allergic reaction, and sometimes …’

Stop, just stop. I’m pleading at her with my eyes, but she is unrelenting.

‘Sometimes people get chest pain, or myocarditis, which is where the lining of the heart becomes inflamed.’

She studiously avoids eye contact with my son and looks directly at my daughter: ‘It’s more common in boys than girls, any questions?’

From the back of the car comes an anxious male voice. ‘How common is it in boys?’ asks my son.

‘Around one in 500,000,’ she answers calmly. ‘Imagine five Wembley Stadiums full of people. Only one will get it.’

And there it is. The nocebo payload is locked, loaded and delivered.

Within a minute, my daughter is, as suggested, feeling unwell. Her head is hurting. ‘But the medicine hasn’t had time to get from your arm to your head,’ I explain.

Later that night my son’s symptoms kick in. His chest is pounding, his heart is hurting and he is genuinely frightened. He is standing alone in a packed Wembley Stadium and everyone around him is cheering. He doesn’t have myocarditis, I am certain, but the thought he could is making him panic.

My children’s symptoms occurred after they received a bona fide vaccine, but they weren’t caused by the vaccine. They were caused by their expectations of it. As new vaccines were developed and further trials were completed, researchers found that the nocebo effect accounted for a whopping 76 per cent of all common adverse reactions after the first dose of the Covid vaccine, and 52 per cent after the second dose.

The same effect has been seen when people have other jabs, such as those for flu.

Vaccines cause side-effects. Some are caused by the active ingredients. Some are caused by how we think we will react. Cholesterol-lowering statins are another persuasive example of the nocebo effect.

Up to a fifth of people stop taking them because of side-effects such as muscle pain. Yet clinical trials show that the rates of muscle pain in those on statins are about the same as those taking placebos.

In one cleverly designed study by Imperial College London, 60 patients who had stopped taking their statins because of the effects were given different bottles – some contained statin pills, others identical-looking placebo pills or were empty.

Critically, the patients didn’t know which tablets they were taking. The researchers found that 90 per cent of the symptoms they experienced on statins were also experienced by them on the placebo pills.