"In general, physicians always have concerns about how emotional stress can have a negative impact on any illness," said Dr. Donald Northfelt, a medical oncologist at the world-renowned Mayo Clinic.
For instance, doctors counsel patients with heart disease to modify their lifestyle to reduce stress, Northfelt said from Scottsdale, Ariz., one of three Mayo Clinic sites in the U.S.
"I think very similar thoughts occur to us when caring for people with cancer, that any aspect of their general health, including their emotional well-being, can have an impact on how the disease plays out."
Stress hormones are known to suppress the immune system, leaving a person more vulnerable to developing infectious diseases like colds or influenza. But Northfelt said there is no strong evidence that prostate cancer — which Layton had earlier battled, followed by an unspecified "second" cancer — is influenced by an immune system not in top form.
Canadian cancer specialist Dr. Matthew Cheung stressed that cancer is a complex disease: there are many different kinds and whether the immune system affects their behaviour would depend on the type of malignancy.
Furthermore, it would be difficult to determine "whether the stress of that campaign and ultimately coming down from the stress may have had any direct influence" on Layton's cancer, said Cheung, a hematologist at Sunnybrook Health Sciences Centre in Toronto who was not involved in his case.
Studies looking for a possible link between stress and the development or progression of cancer have had conflicting results, he said. "It's not been really clear if it's a direct relationship, so for instance: the stress is the cause and the effect is cancer."
And cancer-related behaviours that may go along with stress for some patients — smoking, excess alcohol intake, poor diet and inadequate exercise — make it "hard to specifically tease out stress alone," said Cheung, noting that his comments were general and not related to Layton.
Still, Northfelt said the physical and mental slog on the hustings — criss-crossing the country, rallying the troops and wooing voters with multiple speeches, plotting political strategy — perhaps meant Layton was able to pay less attention to his own well-being than to campaign concerns.
"I think it would be more plausible to suspect that his general level of health may have suffered over the course of all the rigours of the campaign," Northfelt said. "I'm speculating, but he may not have been eating well, he may not have been resting as well as one should in any case, but particularly in a case where one is fighting an illness.
"We know that things can run down a person's general health and might make it more difficult in a battle with an illness like cancer."
Donna Czukar of the Canadian Cancer Society said the organization offers a broad range of support programs and referrals to services aimed at improving quality of life for cancer patients.
"And helping to reduce anxiety or stress helps people with the cancer experience," Czukar, senior director of support programs for the society's Ontario division, said Monday from Hamilton.
"People do need to try to keep themselves strong and to do things that will benefit their general health, that will help them fight cancer. You still need to have rest, you still need to have a healthy diet, you need to do the things that will keep you healthy while you're going through an experience of illness."
One aspect of cancer that's known to severely challenge a person's ability to overcome the disease is the onset of rapid weight loss, a symptom all too heart-wrenchingly evident when Layton made his last public appearance July 25 to announce he was taking a leave of absence to deal with a new cancer diagnosis.
Northfelt said the wasting syndrome, called cancer cachexia, occurs because tumours produce substances that suppress appetite and alter the body's normal metabolism.
"So people don't eat well, they don't assimilate the calories they do eat in the proper way, so they can't sustain themselves, can't sustain their tissues," he said, adding that cachexia "absolutely would" affect the body's ability to defeat the cancer.
Northfelt said he advises his patients that they need to make themselves number 1, to make sure they take care of themselves before they take care of anybody else.
"But oftentimes the care of oneself is neglected."
While it's impossible to know what toll, if any, the election campaign and the day-to-day pressures of being Canada's new Opposition leader took on Layton's health, Northfelt points out that his very public struggle with cancer may have had a bolstering effect.
"My sense from what I read about him was that he was a very beloved person, very highly regarded throughout Canada. I would have to imagine that all that positive regard that he had from colleagues and from people in the public probably supported him to a degree and may have helped him in some way in his illness.