Researchers evaluated 45 male and 44 female undergraduate students from Ohio State University. Each was given a questionnaire on loneliness and was monitored during one task involving mental arithmetic and one task involving writing and giving a speech to defend against a false accusation of stealing.

Researchers found that lonely college students had elevated blood pressure due to increased resistance to flow when performing mentally and emotionally stressful tasks. In contrast, students who did not feel lonely had increased blood pressure from increased cardiac output, a more normal response to stress that is probably healthier in the long term. The lonely students also demonstrated elevated baseline resistance to flow, suggesting that differences in the cardiovascular systems of the two groups were pervasive.

In a parallel study of older subjects, systolic blood pressure rose with age in lonely men and women, whereas it remained more stable in men and women who were not lonely.

This second study recruited 6 men and 19 women, ages 53 to 78 years, from the community. All of the subjects were generally healthy for their age. The subjects were administered the loneliness questionnaire as well as several medical tests to assess their blood pressure and other clinical measures.

Among the subjects who were deemed lonely, blood pressure was significantly higher in the older half of the group than the younger half. In those who were not lonely, blood pressure was similar across the age range. The authors believe that these findings corroborate those from the first study and suggest that loneliness is a relatively stable characteristic across the lifespan.

"Differences in the [mechanisms of blood flow] observed throughout the session in younger adults may contribute to elevated blood pressure across time in lonely adults," says John T. Cacioppo, Ph.D.

Both chronic hypertension and elevated vascular resistance have been linked to increased risks of heart disease.

The study also showed that lonely people were no different from the non-lonely in terms of behavioral risk factors such as drinking, smoking, diet and compliance with medical treatments. The authors suggest that this may mean researchers need to look elsewhere to understand the apparent increased risk of disease in the group with mood problems.

"Previous research has shown that passive coping is associated with elevated [blood pressure] due to vascular resistance, whereas active coping is associated with elevated [blood pressure] due to increases in [cardiac output]," the authors say. "The parallels between these findings are suggestive in light of recent evidence that lonely individuals are less likely throughout the day to actively cope and more likely to feel anxious and threatened than non-lonely individuals."