In late 2009 I came across a web link that changed my life. On about page 20 of a Google search I stumbled upon an academic paper written by an Australian MD and university professor named Craig Hassed which highlighted the emergence of evidence-based mind-body medicine.

At the time I was very sick. I’d been diagnosed with an autoimmune disease four years before and had spent a fortune trying everything that both conventional and alternative medicine had to offer. The paper, which was called “Mind-Body Medicine: Science, Practice and Philosophy,” outlined research linking the brain to the immune system, the importance of group support in improving outcomes for sick people, and how stress reduction techniques (such as meditation) can improve immune function. It gave me a credible, reliable, and trustworthy path to follow. Regular readers will know that it also inspired me to make my film The Connection: Mind Your Body.

I have Craig to thank for the fact that I’m extremely well today, so when an email landed in my inbox from the man himself, I sat up and took notice. From time to time we have discussions about scientific papers that are hot off the press and after he’d read one of my recent posts about the stress–health connection, he wanted to query a study I’d referred to because it showed that stress did not influence the likelihood that a woman with a strong family history of breast cancer would develop the disease.

Craig asked if I’d considered whether the women’s perceived levels of stress had been included in the breast cancer study. This is an important issue because one person’s nightmare can be another person’s triumph. For example, as Craig pointed out, a divorce could be a stressor for one woman but a major release of stress for another. “It is all in the perception of the event, not the event itself,” he wrote.

I went back to the breast cancer-stress study and it turned out the researchers had not directly addressed perceived stress. They stated that they “controlled for a very comprehensive list of potential confounders, but some aspects (such as coping style) were not assessed.”

These days “stress” is a catch-all phrase we apply to a variety of negative mental states and circumstances. Moving house is stressful. So is being homeless. Years of infertility are stressful. So is wrangling two children under the age of three in a supermarket. No matter where we sit on the continuum of life circumstances, when we say we're feeling stressed, we're probably referring to a negative, subjective feeling of being overwhelmed by the amount of responsibility we face.

I started a deep dive into the emerging scientific evidence looking at perceived stress and its role in illness three years ago when I was writing my book. I learned for example that in the 1960s and 1970s John Wayne Mason found that our perception of a stressful event was critical to how our body responded to it. Whereas one person may be consumed by terror at the thought of public speaking, another might see it as an exciting challenge. More recent research shows that each person’s performance and biology responds accordingly.

But three years is a long time in scientific research and Craig’s email prompted me to see where things are now. It turns out, even more evidence has mounted. For example data from a global survey of nearly 230, 000 people showed that people who reported feeling higher levels of stress were more likely to have a chronic illness. Another study of over 100, 000 people in Denmark found a dose–response relationship between perceived stress levels and the probability of needing primary care services. That is to say, the more stressed people felt, the more likely they were to see a doctor, go hospital, or require antidepressant drugs.

Significantly, a study of 664 women with breast cancer were asked if events occurred prior to their diagnosis and if they considered those events to be stressful or not. Once again, the researchers found a dose-response relationship. The more stressful the women felt events had been, the more likely they were to have breast cancer.  

The important thing I take away from all this is that perceived stress is crucial in the stress-equals-illness equation. When I reread the stress-doesn’t-cause breast cancer study that sparked my dialog with Craig I was disheartened by its conclusion that women at high-risk of breast cancer should concentrate their efforts on monitoring, drugs and surgery. In other words, the researchers are saying don’t worry about stress management, just have regular check-ups and if you get sick, then the best treatment is drugs and surgery.

As I wrote in my piece Does Stress Make You Sick? The Stress-Health Connection, we need to shift the conversation from stress as being a symptom-aggravator and start talking about stress as being a disease-cause. But as Craig pointed out, we also need to have a more nuanced conversation about stress. I can’t help but imagine a world where teaching people how to manage their stress was not only integral to disease management, but also fundamental in disease prevention. I strongly suspect that the chronic illness epidemic would lose its momentum.