The following lifestyle changes have been studied in connection with breast cancer.
Exercise and prevention
Girls who engage in a significant amount of exercise have been reported to be less likely to get breast cancer as adults.1 Although some doctors speculate that exercise in preadolescent girls might reduce the risk of eventually getting breast cancer by reducing the number of menstrual cycles and therefore exposure to estrogen, these effects may occur only in girls engaging in very strenuous exercise.2
Most,3, 4 but not all,5 studies find that adult women who exercise are less likely to get breast cancer. Women who exercise have also been reported to have a reduced risk of high-risk mammography patterns compared with inactive women.6
Exercise in adulthood might help protect against breast cancer by lowering blood levels of estrogen or by helping maintain ideal body weight. In addition to the preventive effects of exercise, aerobic exercise has been reported to reduce depression and anxiety in women already diagnosed with breast cancer.7
Smoking and risk
Some studies have found an association between smoking and an increased risk of breast cancer, including exposure to secondhand smoke.8 However, several reports have either found no association9 or have reported an association between smoking and an apparent protection against breast cancer.10 Some of the studies reporting that smoking is detrimental have found that exposure to cigarette smoke during childhood appears to be most likely to increase the risk of breast cancer.11
The mind-body connection
In some studies, the risk of breast cancer has been reported to be higher in women who have experienced major (though not minor) depression in the years preceding diagnosis.12 Some,13, 14 but not all,15 studies have found that exposure to severely stressful events increases a woman's chance of developing breast cancer. In one study, breast cancer patients exposed to severely stressful events, such as death of a spouse or divorce, had more than five times the risk of suffering a recurrence compared with women not exposed to such stressors.16 Although stress has long been considered as a possible risk factor, some studies have not found significant correlations between psychological stressors and breast cancer risk17 or the risk of breast cancer recurrence.18 Similarly, experiencing psychological distress (independent of external stressors) has, in some reports, not been associated with a reduction in survival or the risk of suffering a breast cancer recurrence.19
Exposure to psychological stress has been reported to weaken the immune system of breast cancer patients.20 Strong social support has been reported to increase immune function in breast cancer patients.21 These findings suggest a possible way in which the mind might play a role in affecting the risk of a breast cancer recurrence.22, 23
In one study, breast cancer patients with strong social support in the months following surgery had only half the risk of dying from the disease during a seven-year period compared with patients who lacked anyone to confide in.24 After 1025 and 15 years,26 breast cancer patients with a helpless and hopeless attitude or with an attitude of stoicism were much less likely to survive compared with women who had what the researchers called a "fighting spirit." In a five-year study, the same helpless/hopeless attitude correlated with an increased risk of recurrence or death in breast cancer patients, but a "fighting spirit" did not correlate with special protection against recurrence or death.27 One trial reported that psychological therapy for hopeless/helpless breast cancer patients was capable of changing these attitudes and reducing psychological distress in only eight weeks.28
Several trials using a variety of psychological interventions have reported increased life expectancy in women receiving counseling or psychotherapy compared with women who did not receive psychological intervention29--even in women with late-stage disease.30 In a now-famous trial, late-stage breast cancer patients in a year-long, 90-minute-per-week support group lived on average twice as long as a group of similar patients who did not receive such support.31
Finally, relaxation training has been reported to reduce psychological distress in breast cancer patients,32 and group therapy and hypnosis have reduced pain in late-stage breast cancer patients.33
Even extensive psychological support (weekly peer support, family therapy, individual counseling, and use of positive mental imagery) has not led to a clear increase in breast cancer survival in every study.34 Why some studies clearly find mind-body connections in regard to breast cancer risk, recurrence, or survival, while other studies find no such connection, remains unclear.
Being overweight increases the risk of postmenopausal breast cancer, a fact widely accepted by the research community. Overweight does not increase the risk of premenopausal breast cancer and even may be associated with a slightly reduced risk of breast cancer in young women.35