The immune system is a funny animal. It's job is to protect the rest of the body, but it can be affected by the health of the rest of the body too – even mental health.
A recent study found that untreated depression in older adults can weaken the effectiveness of the shingles vaccine.
Shingles is caused by the varicella zoster virus. The varicella zoster vaccine is recommended by the CDC for all adults aged 60 and older.
But if you are depressed and not treating your depression, your body's response to the vaccine may be weaker than if you were taking antidepressants or weren't depressed.
The study, led by Michael R. Irwin, MD, of the UCLA Semel Institute for Neuroscience at the University of California Los Angeles, looked at whether depression had any influence on the effectiveness of the shingles vaccine.
The researchers followed 92 adults who were at least 60 years old for two years. Forty of these adults had major depressive disorder, and the other 52 were matched to those 40 by age but had no history of depression or another mental disorder.
All the adults had their immunity levels to shingles tested before they received either the shingles vaccine or a placebo (fake) injection. Then the researchers checked the participants' shingles immunity cells six weeks after the injection, and then again one and two years later.
The researchers found that the depressed adults who were not taking antidepressants for their mental illness had lower levels of shingles immunity than those who were taking antidepressants or weren't depressed.
Even if the depressed participants who were taking antidepressants did not appear to have lessened symptoms of depression, their immunity levels were still higher than the depressed adults who took no antidepressants.
The level of immunity was assessed by measuring the "cell-mediated immunity" to the varicella zoster virus (VZV-RCF). Six weeks after the vaccines (or placebos) were given, the untreated depressed patients had a VZV-RCF score of four per 100,000 blood cells.
Meanwhile those with no depression had a score of 11 per 100,000, and those with depression taking antidepressants had a score of a little over nine per 100,000.
This means those who were taking antidepressants for their depression had roughly twice the immune response as those who were depressed but untreated.
These patterns were similar at one and two years after the vaccine. A year later, depressed patients only had two VZV-RCF per 100,000 blood cells, compared to five for non-depressed patients and six for those who were depressed but taking antidepressants.
"Depressed patients have diminished [shingles immunity] responses to zoster vaccine, and treatment with antidepressant medication is associated with normalization of these responses," the researchers wrote. "Untreated depression may increase the risk and severity of [shingles] and reduce the efficacy of [the shingles] vaccine."
The study was published February 14 in the journal Clinical Infectious Disease. The research was funded by the National Institute of Mental Health, the National Institutes of Health, the Veterans Administration Cooperative Study Program, a grant from Merck & Co., the UCLA Clinical and Translational Science Institute, the Cousins Center for Psychoneuroimmunology and the James R. and Jesse V. Scott Fund for Shingles Research. One author reported receiving research and consultancy funds from Merck.