The connection between excess worry and increased disease risk is not just hypothetical. Numerous studies have shown a link between ill health and stress reported by patients. Special health conditions for which research has shown an impact from stress include:

* Heart disease, cancer, chronic lung disease A 1998 study in the American Journal of Preventive Medicine showed a strong relationship between childhood anxiety growing out of a dysfunctional household and multiple risk factors for leading causes of death in adults, including heart disease, cancer and lung disease.

* Coronary heart disease The American Heart Association cites research linking stress with risk for coronary heart disease. Stress may affect behavior, which in turn affects health. For example, people under stress may overeat, start smoking or smoke more than they otherwise would.

* Cancer Some studies of women with breast cancer have shown significantly higher rates of disease among those who experienced traumatic life events and losses within several years before diagnosis. Although studies have shown that stress factors (such as the death of a spouse, social isolation and medical school examinations) alter the way the immune system functions, they have not provided evidence of a cause-and-effect relationship between these immune system changes and the development of cancer.

* Stroke A 2000 study of more than 2,000 middle-aged men in the journal Stroke showed three times greater incidence of fatal stroke for those suffering from anxiety or depression.

* Overall health Studies in Israel have shown that terrorism and fear have a cumulative effect on health. Suicide bombings in 2001 were shown to impact the personal sense of safety in 2002. A study in the journal Psychosomatic Medicine showed that Israeli women who expressed fear of terrorism had twice the level of an enzyme that correlates with heart disease as did similar women who weren't worried.

-- Marc Siegel