Does Stress REALLY Cause Cancer? With research showing half of all cases are due to lifestyle, we ask the world’s leading experts if trauma could be a trigger

It’s a controversial question that has long divided the world’s leading scientists: Can stress cause cancer?

For years, physicians treating patients have often noted that major life events—grief, divorce, and severe trauma—often occur in the years just before the onset of the disease.

Yet the actual evidence is far from conclusive. Even Cancer Research UK (CRUK) says the links are not only unproven but may be nothing more than a myth.

But with stress levels rising and the number of people with cancer expected to increase by a third to four million by 2030, some cancer experts now say there is new evidence about the impact of stress on the body and that it would be ‘not surprising’ if there is a link between the two.

Professor Melanie Flint from the University of Brighton, who researches the influence of stress hormones on cancer, said: ‘There has been a lot of progress in this area and I don’t think we can rule out that stress plays a role in cancer.

“I believe it does contribute to the development of cancer and to the spread of cancer once you have cancer. However, it is a contributing factor, not necessarily a direct cause.”

Some studies, which have followed large populations over long periods of time, seem to confirm this.

A study of 10,000 women in Finland followed for 15 years found that women who had lost a loved one had a greater chance of developing breast cancer within five years.

Exposure to stress at work has been associated with an increased risk of prostate cancer in men under 65 and, although this was a weaker link, with breast cancer in women.

However, other similar studies – including reviews of the best evidence – show no association at all.

According to Professor Trevor Graham, director of the Centre for Evolution and Cancer at the Institute of Cancer Research, part of the problem is that stress is often associated with other behaviours that also increase cancer risk.

‘A stressful life can be associated with many other risk factors for cancer, such as smoking, excessive alcohol consumption, inactivity and an unhealthy diet, so it is difficult to separate out the causative factors,’ he says.

What we do know is that stress has a range of effects on the body, especially when it is chronic.

Professor Flint says: ‘Stress causes the production of the stress hormone cortisol.’

Cortisol binds to receptors located on every cell, thereby regulating several other processes, including inflammation.

‘Stress and cortisol can also suppress the immune system.’

Scientists have also tried to mimic the effect of stress on cells in the lab, showing that stress damages DNA and causes changes in cells that, if allowed to multiply, can lead to cancer.

But because stress is difficult to model, this may not be a good indication of what is actually happening in the human body, Prof Graham points out.

It is also likely that most people can repair this damage naturally.

But there is one notable exception: people with genetic mutations that already put them at higher risk of cancer – such as those with the ‘Angelina Jolie’ genes BRCA1 and BRCA2, named after the Hollywood actress, which she inherited from her late mother, who died from the disease – may be less likely to develop cancer, Professor Flint says.

“If someone has a cancer mutation that affects how well they can repair DNA, like BRCA, they may be more vulnerable to the effects of stress,” she says.

“We can’t say that if you are very stressed and you have a cancer mutation, that you will definitely get cancer. We still don’t understand all the underlying mechanisms.

“But we have to be aware that it may pose an additional risk for some people and that stress needs to be managed.”

There is also limited evidence, she adds, that stress may indirectly increase cancer risk by triggering flare-ups of viruses such as the human papillomavirus (HPV), which has been linked to cervical cancer.

The strongest evidence, however, is that stress may play a role in the spread of cancer after it has already developed.

Professor Nazanin Derakhshan from the University of Reading said: ‘There is some evidence that anxiety and depression in breast cancer increase the risk of recurrence and mortality.

‘More and more studies are reporting this and we cannot ignore it.’

Professor Flint says cortisol may help cancer cells evade the immune system and spread from the original tumour site to a secondary site.

‘If you are stressed and your immune system is weakened as a result, or if stress hormones act on the cancer cells themselves, the cancer cells can hide from the immune system and, depending on the type of cancer, spread to more difficult to treat areas such as the brain, lungs, bones and liver.

‘The evidence that stress can cause cancer may not yet be clear, but it is clear that stress can cause existing cancer to spread.’

More evidence will likely emerge.

Professor Charles Swanton, lead clinician at CRUK, said: ‘In the next five to 10 years we may see data emerge testing the link between stress and cancer.’

In the meantime, Professor Flint advises helping people who already have cancer, or those with a genetic mutation that increases their risk, to manage their stress levels.

This may include talk therapy, medication, exercise, or simply “taking care of yourself.” These are all good for you, whether you have cancer or not.