Comorbidity between physical illness and psychiatric illness has been a focus of research initiatives for a number of years (Psychiatric News, July 7). Only recently, however, has the evidence become increasingly clear just how strong the connection is between mind and body.

The relationship between stroke risk and depression is one example of the link. A new study reported in the May/June issue of Psychosomatic Medicine confirms that strokes occur 2.6 times more often in some patients who have a history of depressive symptoms than in those who have not endured a depressive illness.

Bruce S. Jonas, Sc.M., Ph.D., an epidemiologist in the Office of Analysis, Epidemiology, and Health Promotion at the National Center for Health Statistics, a division of the Centers for Disease Control and Prevention, and his coworkers reviewed data on 6,095 stroke-free individuals aged 25 to 74 who had participated in the National Health and Nutrition Examination Survey and its corresponding Epidemiologic Follow-up Study.

The study included both men and women and both whites and African Americans. Individuals were followed for an average of 16 years, though some were followed for as long as 22 years.

The relationship between stroke and self-reported baseline depressive symptoms was analyzed, and the researchers adjusted for such known risk factors as baseline age, race, sex, education, tobacco use, body-mass index, alcohol use, level of nonrecreational activity, serum cholesterol, systolic blood pressure, and history of diabetes or heart disease. All of these factors have been linked in earler studies to increased likelihood of stroke. The General Well-Being Schedule, Cheerful vs. Depressed Mood Scale (GWB-D) was used to assess depressive symptoms.

Adjusting for age, subjects of both races and both sexes showed a significant correlation between depression and the prediction of stroke. Even when the researchers adjusted for both age and other risk factors known to be predictive for stroke, the association between depression and prediction of stroke remained, although the relationship was no longer as strong.

White men with high levels of depressive symptoms were, for example, 1.88 times more likely to suffer a stroke than those with low levels of depressive symptoms. When the researchers adjusted for other known risk factors, such as hypertension, cardiovascular disease, smoking, age, sex, and so on, the increased stroke risk remained at 1.68 times the risk for nondepressed white males.

White women with high levels of depressive symptoms were 1.86 times more likely to suffer a stroke than those with low levels of depressive symptoms. After adjusting for known risk factors, the relative risk remained at 1.52.

For African Americans of both sexes with high levels of depressive symptoms, the relative risk of suffering a stroke was 2.18 times that of nondepressed black individuals. Interestingly, after adjusting for the known risk factors, depression was even more predictive in blacks for the likelihood to suffer stroke, at 2.6 times that of nondepressed black individuals.

The researchers also looked at whether the incidence of stroke was correlated with other psychiatric illness. Knowing that depression and anxiety go together (75 percent concordance in this study), Jonas, adjusting for the presence of comorbid anxiety, determined that anxiety was not significantly related to stroke.

Having determined that depression is correlated with a greater likelihood of having a stroke, Jonas looked at "cheerfulness," as an opposite to depressive symptoms, to see if it reduced the likelihood of stroke.

After adjusting for risk factors, age, and sex, cheerfulness did not turn out to be a significant protector against suffering a stroke.

Jonas and his colleagues also looked at the sense of "hopelessness," as defined in the GWB-D, to determine if it might predict increased likelihood of stroke. Once again, after adjusting for other known risk factors, Jonas determined that stroke was associated with severe levels of hopelessness.

He concluded that the findings from this study "lend additional support to a significant association between depressive symptoms and subsequent stroke occurrence." He was quick to point out the study’s limits, however, including the self-report method by which they determined whether subjects had a history of depressive symptoms. In addition, inaccuracy of baseline history, inaccuracy of history of hospitalization for stroke, and inaccuracy of diagnoses each patient received, in the absence of copies of medical records or death certificates, could all have skewed the results.

Jonas noted that additional studies are needed to address these limitations as well as to verify his group’s conclusions. Then, he added, the question will be, "can we reduce the incidence of stroke through better diagnosis and treatment of mental disorders?"