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A study of elderly widows and widowers seeking treatment for bereavement-related depression has found evidence that stress-related sleep disruptions weaken immunity.
Investigators studied 29 widows and widowers undergoing their first episode of major depression. Participants spent three nights in a sleep lab and provided blood samples. Those who slept most poorly had decreased levels of natural killer cells (NKC's) in their blood, suggestive of impaired immunity. The study by psychologist Martica Hall, Ph.D., and colleagues in the department of psychiatry at the University of Pittsburgh School of Medicine was published in the January 23 issue of Psychosomatic Medicine ("Sleep as a Mediator of the Stress-Immune Relationship").
Hall spoke with Psychiatric News about what the study might mean for clinicians.
Although sedatives can temporarily enhance sleep, and hence minimize sleep disruptions, they are at best a transient approach, said Hall.
"It is better to treat the underlying problem. Sure, a sleeping pill will help you sleep. But you need to address the underlying problem to sleep better in the future and have a better quality of life in the future."
To the extent that people come to terms with their loss and sleep better, they will be at lower risk of infectious illnesses than someone who hasn't come to terms with their loss and continues to sleep poorly for an extended time, Hall explained.
"The thing that [other media have] overlooked in this article is the role of intrusive thoughts," said Hall. "What we found is a triangle: The more people tried to avoid thinking about their loss, the harder it was to sleep. And the sleep-onset disruptions were associated with lower natural killer cell numbers."
Earlier studies have shown a link between stress and immunity, observed Hall. When stress causes sleep disruption, the inability to sleep becomes another stressor, she noted. Helping patients sleep normally is, therefore, likely to help them remain healthy by helping their immune systems to function normally.
The measure employed by Hall, NKC's, is a nonspecific immune response. NKC's attack viruses and cancer cells. There are two aspects of this-number and function. Hall looked at numbers.
Michael Irwin, M.D., an associate professor of psychiatry at the University of California at San Diego, has done extensive research on the relationship between sleep and immunity. He spoke with Psychiatric News about Hall's study.
The study replicates some earlier work with depressed patients but breaks new ground by extending the investigation to the naturally occurring stressor of bereavement, said Irwin.
"We have been struggling as a field to identify what may be mediating immune changes in stressed and depressed patients," he commented. "As we gain a better understanding of [the stress-immunity relationship], we may be able to design specific interventions to reverse or alleviate the immunological declines associated with stress and depression."
For example, he added, if Hall had found that it was anxiety and not sleep that mediated immune response, then it would make sense to develop cognitive or psychopharmacological interventions focusing on anxiety rather than sleep. Since there are now several studies focusing on sleep as a mediator, however, it makes sense to focus on understanding what is occurring during sleep that leads to these changes, Irwin said.
"I think these findings also have much broader implications beyond stress and depression because they further support the idea that sleep is involved in the homeostatic regulation of the organism, and the idea that when sleep is disordered there can be impaired functioning of multiple systems of the body, with potential impact on health and disease outcomes," he added. "This is yet one more study that shows that sleep is playing an important role in changes in the immune system." -R.B.K.