People who experience symptoms of depression are at an increased risk of developing stroke, suggest the results of a two-decade study conducted by the Centers for Disease Control and Prevention (CDC).

There was a 73 percent increase in stroke risk among study participants with high levels of depression symptoms according to the researchers from the CDC. They also found a 25 percent increase in stroke risk associated with moderate levels of depression symptoms. The relationship of stroke risk and high depression also varied by race and gender.

There was a 68 percent increase for white men, a 52 percent increase for white women, and a 160 percent increase for African Americans.

“The suggestion of an increasingly strong relationship between level of depressive symptoms and stroke indicates that reducing depression may be important for everyone, not just those whose symptoms may have clinical implications,” said lead author Bruce S. Jonas, ScM, PhD, of the CDC’s National Center for Health Statistics in Hyattsville, MD.

The researchers followed a nationally representative sample of 6,095 stroke-free adults 25 to 74 years old in the early 1970s as part of the first National Health and Nutrition Examination Survey. Participants were followed for a maximum of 22 years by completing a series of questionnaires probing their health history and psychological symptoms.

The increased risk of stroke for individuals with symptoms of depression persisted even after controlling for other stroke risk factors including baseline age, gender, race, education, smoking status, body mass index, alcohol use, physical activity, serum cholesterol level, systolic blood pressure, history of diabetes, and history of heart disease.

“Risk factors such as baseline age, gender, smoking status, systolic blood pressure, serum cholesterol level, history of diabetes and history of heart disease remain strong predictors of developing stroke” said Jonas. “However, this study indicates that elevated depression levels may also play an important role.”

Overall, 9.1 percent of all participants reported high levels of depression and 32.7 percent reported moderate levels at the beginning of the study. Among African Americans, 15.7 percent reported high levels of depression, compared with 10.4 percent of white women and 5.6 percent of white men according to the study.

The exact mechanism by which depression may increase stroke risk is not understood, noted the researchers. Previous research suggests depression’s effect on the nervous or immune systems may play a role. Depression may also increase the risk of diseases such as hypertension, that in turn increase stroke risk.

“Intervening hypertension might explain, at least in part, the pathway from depression to stroke as well as the higher risk of stroke among depressed African Americans,” said Jonas. African Americans are known to suffer from higher rates of hypertension and, based on previous research by Jonas and others, depressed African Americans have higher risks of hypertension compared to other groups.

Funding for this study was provided by the National Institute on Aging; National Center for Health Statistics; National Cancer Institute; National Heart, Lung, and Blood Institute; National Institute of Arthritis, Diabetes, and Digestive and Kidney Diseases; National Institute of Mental Health; National Institute of Alcohol Abuse and Alcoholism; National Institute of Allergy and Infectious Diseases; and the National Institute of Neurological and Communicative Disorders and Stroke.

The findings are published in the July/August 2000 issue of Psychosomatic Medicine.