And while conventional medicine still disputes the link, women themselves know instinctively that stress is influential. In a study of nearly 400 breast cancer survivors who had been disease-free for nine years, 42 per cent said they believed that stress was one of the main causes of their breast cancer (Psycho-Oncology, 2001; 10: 179-83). This idea has been confirmed by scientists who have found that women under stress from bereavement, job loss or divorce have almost a 12-fold increased risk of developing breast cancer within five years (BMJ, 1995; 311: 1527-30).
Stress, memory and mood
Stress doesn’t just poison the physical body; it also has a profound effect on our mind and mood. The same HPA activity that causes physical disorders in some can cause mental and emotional disorders in others.
Long-term stress can also affect memory by destroying neurons in the hippocampus, the area of the brain that contributes to visual memory and context (J Neurosci, 1989; 9: 1705-11; Sapolsky RM, Stress: The Aging Brain and the Mechanisms of Neuron Death, Cambridge, MA: MIT Press, 1992). Poor dietary habits associated with stress may also contribute to a range of psychological problems such as depression and anxiety (J Am Diet Assoc, 2002; 102: 699-703).
Stress can also contribute to disease like Alzheimer’s. Hormones such as cortisol - increased during stress - block the ability of glucose to gain entry into brain cells. Unlike other tissues, glucose is the only source of energy for the brain, and some structures, like the hippocampus - that part of the brain that helps to maintain learning and memory skills, particularly the kind of short-term memory that allows you to remember the list of things you went to buy at the supermarket - are affected more by this deprivation than others.
In addition, there is evidence to show that women with Alzheimer’s tend to have low levels of DHEA in relation to cortisol (Psychopharmacology [Berl], 1993; 111: 23-6).
Worse, a daily dose of stress hormones can cause the hippocampus to shrink. There is evidence, for instance, that the hippocampus of individuals suffering from post-traumatic stress disorder (PTSD) as a result of serving in the Vietnam war or because of childhood abuse is significantly smaller than normal (Biol Psychiatry, 1999; 45: 797-805; Arch Gen Psychiatry, 2000; 57: 925-35).
Depressed individuals often have significantly higher morning and midnight salivary cortisol levels (Am J Psychiatry, 1991; 148: 505-8; Biol Psychiatry, 1987; 18: 1-4; Eur Arch Psychiatr Neurol Sci, 1987; 237: 36-45) and disrupted circadian rhythms (Psychiatr Res, 1990; 37: 237-44; Horm Res, 1982; 16: 357-64; Arch Gen Psychiatry, 1973; 28: 19-24). At the extreme end of the scale, about 60.6 per cent of patients with chronic schizophrenia also show abnormal cortisol levels (Neuropsychobiology, 1992; 25: 1-7).
While depressed patients frequently complain of difficulties with concentration and memory, the problems associated with higher cortisol levels don’t begin and end with memory. In the same way that higher cortisol levels in athletes who have exercise-related amenorrhoea (lack of menstrual periods) correlate with significantly low bone mineral density (Ann Intern Med, 1988; 108: 530-4), women with a history of depressive illness - characterised by chronic, moderately raised levels of serum cortisol - are also more likely to have decreased bone mineral density (N Engl J Med, 1996; 335: 1176-81). These findings mirror those in women who have had their ovaries removed - an operation that can lead to osteoporosis and poor calcium absorption - again as a result of increased cortisol levels (Lancet, 1979; ii: 597).