Even Mild Depression Harms Immunity

Chronic Stress, Clinical Depression Dampen Immunity

From the WebMD Archives

Oct. 15, 2003 -- New research shows clinical depression, even in its mildest form, takes a toll on the immune system. It gives a foothold to serious health problems.

A new study offers a clear picture of how the body responds to clinical depression. It builds on 25 years of research aimed at understanding the link between stress, depression, and immunity.

Lead researcher Ronald Glaser, PhD, a professor of molecular science, immunology, and genetics at Ohio State University in Columbus, reports his findings in this month's Archives of General Psychiatry.

His study involved 119 older people, all around age 71. Of these, 23 were taking care of spouses with dementia or Alzheimer's disease -- generally a high-stress situation, and 24 were formerly caregivers whose spouses had died. The rest had never been caregivers.

Each got a flu vaccine shot. Vaccines produce an immune response, so they are a good indicator of immune health, writes Glaser.

But before their flu shots, each volunteer had a blood test to measure interleukin-6 (IL-6) levels -- a measure of inflammation in the body. Higher IL-6 levels and inflammation has been linked to disability in the elderly as well as certain conditions associated with aging, such as heart disease.

Each participant was also tested for clinical depression.

Two weeks after the flu shot, they had blood tests done again.

  • Those 58 people with clinical depression symptoms had substantially higher IL-6 levels -- and thus more inflammation -- both before and after their flu shots.
  • Those who did not have clinical depression had lower IL-6 levels.

Current caregivers were more likely to have clinical depression than others in the study. They also had the highest IL-6 levels before and after their flu shots.

"Higher levels of depressive symptoms in current caregivers were likely a key factor in their increased IL-6 levels," writes Glaser. The finding points directly to the effect of chronic stress on immunity, he adds.

Stress Unbalances Immunity

A growing body of evidence has shown that the stresses of caregiving greatly unbalance the immune system. Caregivers take 24% longer to heal when they have small wounds. Caregivers also have more illnesses and infections that last longer.

"Increased susceptibility to infectious disease and poorer recovery from infection are substantial and important problems," says Glaser.

In fact, high levels of IL-6 -- for long periods of time -- can trigger long-term changes in the body's physiology. These changes lead to age-related illnesses, such as heart disease, osteoporosis, arthritis, type 2 diabetes, lymphoma and other cancers, and Alzheimer's disease, Glaser writes.

These changes also fuel decline in physical function, leading to frailty, disability, even death, he says.

All this points to the serious nature of even mild forms of clinical depression -- and the need to get treated. Also, it points to the importance of flu shots, Glaser says. Especially if you are depressed, you are more likely to get sick without the vaccine.

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SOURCES: Archives of General Psychiatry, Oct. 2003; vol 60: pp 1009-1014. News release, Ohio State University.
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