A link between exposure to traumatic stress and cancer has long been suspected—but researchers don’t yet fully understand how severe stress could produce this insidious effect or which types of cancer might be most affected. A new study of cancer risk amongst Holocaust survivors offers some clues.
The research also suggests that very low calorie diets—which other studies find to be protective against cancer—almost certainly aren’t when they are imposed by force under traumatic conditions.
The study was published in the Journal of the National Cancer Institute and conducted by researchers at the University of Haifa in Israel who searched Israel’s cancer registry. It compared cancer rates amongst 315, 544 Jews, who immigrated to Israel from Europe before or after 1945. The 258,048 who arrived in Israel after 1945 were presumed to have had significant exposure to the Holocaust—while those who immigrated before that would have had little or no experience in death or concentration camps.
The study found a 17% increase in risk for all types of cancer. The younger someone was during the Holocaust, the higher the risk for cancer. This was especially severe for infants and toddlers. For example, male survivors born between 1940 and 1945 had an overall risk of cancer 3.5 times higher than those who were not exposed to the Holocaust, while the risk for women in that age group was 2.3 times higher.
Breast cancer risk was mostly strongly affected for women, again concentrated amongst those who had been under 5 during the Holocaust. These women had a 2.44 times greater chance of getting breast cancer. The risk of colorectal cancer, however, was most affected amongst those who were 6-10 during the war, with odds increased by a factor of 1.75 for men and 1.93 for women.
So how could trauma exposure—particularly during childhood—affect cancer risk? “The best data suggests that it may be through inflammation,” says Janice Kiecolt-Glaser, PhD, Professor of Psychiatry at Ohio State University College of Medicine, who has studied the link between severe stress and health problems.
Kiecolt-Glaser adds, “There is growing evidence that inflammation is a risk factor for a number of different cancers and also for mortality from cancer. There is lots of evidence that stress enhances inflammation, and talk about severe stress! The Holocaust is certainly that.”
Childhood stress is most damaging. “There’s very good evidence that childhood adversity is associated with a higher level of inflammation in adulthood and that may persist over time,” she says, “Kids who been traumatized in a variety of ways–like long term physical or sexual abuse– appear to have higher level of inflammation. That could be very a reasonable mechanism that could contribute to increased risk of cancer here.”
Kiecolt-Glaser adds, “Breast cancer is not one that we typically think of as being stress related.” Earlier research has not found consistent connections. But the fact that trauma exposure in the earliest part of life is most dangerous suggests a mechanism that may be involved.
In late pregnancy and early childhood, genes are highly susceptible to environmental influences that set the course for later development. Jewish women from Eastern Europe are known to have a higher genetic risk for breast cancer. “I wonder if what we might have here is group might that be more susceptible in the face of overwhelming stress,” she says.
A large body of (mostly animal) research suggests that starvation or near-starvation level diets might actually prolong life and cut cancer risk. However, this study shows that forced caloric restriction under traumatic conditions—particularly early in life—has the opposite effect.