New research at the University of California, Davis, bolsters long-held suspicions that emotional stress can weaken the body's defenses against AIDS-type viruses and even hasten death.
Psychologist John Capitanio and colleagues found that in monkeys with an AIDS-like illness, those allowed to form stable social relationships lived longer than those whose social groups continually changed.
The findings have important implications for people with AIDS, Capitanio said.
"Around the world, people with AIDS can experience substantial social stress from a variety of sources," he said. "Many are shunned by friends and family, discriminated against in the areas of insurance, jobs and housing, and even physically attacked. Many also experience the deaths of partners and close friends.
"Our data provide strong evidence that such stresses can have an impact on the course of the disease itself."
The new study appears in the April 14 issue of the journal Proceedings of the National Academy of Sciences. It was inspired in 1991, when Capitanio and a UC Davis colleague, Nicholas Lerche, reviewed post-mortem records of rhesus macaque monkeys infected with simian immunodeficiency virus (SIV) in several monkey colonies in the United States.
They discovered that the monkeys that had been separated from familiar companions died earlier than those that had not.
Intrigued, Capitanio began a prospective study to examine the physical effects of social stress in monkeys with SIV. Working with him were Lerche and UC Davis psychologists Sally Mendoza and William Mason.
Eighteen healthy, male, young-adult rhesus macaques were infected with SIV. Then all the monkeys were given frequent, equal periods of social contact with other monkeys. However, while half of the animals were always grouped with the same individuals, in "stable" associations, the other half were grouped with a variety of individuals, in "unstable" associations.
Social conditions had a significant impact on survival. The monkeys in stable groups lived an average of 40 percent longer than those in changing groups -- an average of 588.5 days compared to 420 days.
Early measures of infection -- levels of virus and infection- fighting antibodies in the blood -- also predicted survival.
But surprisingly, social conditions did not predict early measures of infection. That is, the monkeys in stable groups didn't have significantly better early blood tests than the ones in unstable conditions, Capitanio said.
What did predict early measures of infection? Behavior, regardless of social condition. In both stable and unstable groups, the monkeys that received the most aggression from other monkeys had the worst blood-test results.
"Overall, animals in unstable associations did worse than did animals in stable associations. However, early on, it was clear that some unstable monkeys were somewhat protected by their greater ability to navigate the stormy social waters," Capitanio said.
"Plus, there were a couple of monkeys in stable social groups that had difficulty fitting in. So the question becomes, what distinguishes the individuals who did fairly well from those who didn't do so well? We suspect it has to do with a monkey's personal style of coping with stressful situations.
"That's the focus of our next study -- the interaction of these personality characteristics and social situation, how stress-related hormones are affected, and how the hormones affect the disease process."
For now, the study suggests some courses of action. "Public education aimed at reducing the stigma associated with this disease can help to reduce social stresses; moreover, availability of support services for people with AIDS might buffer some of the negative effects of socially induced stresses," Capitanio said.
Details of Capitanio's earlier, retrospective study of social separation, housing and simian AIDS will appear in the May 22 issue of the journal Psychosomatic Medicine.
All the research was funded by the National Institute of Mental Health and the National Center for Research Resources.
The above story is based on materials provided by University Of California, Davis. Note: Materials may be edited for content and length.
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