Accelerated Immune Cell Aging Linked to Chronic Depression
The findings indicate that accelerated cell aging does not occur in all depressed individuals, but is dependent upon how long someone is depressed, particularly if that depression goes untreated.
"There's a lot more to depression than feeling blue," said first author Owen Wolkowitz, a professor of psychiatry at UCSF.
"As if feeling depressed is not bad enough, we are finding that long-term depression may be associated with damage to cells in the body, and this may predispose patients to certain physical diseases."
In probing the links between depression and physical disease, the research team explored aging of the immune system as measured by the shortening of telomeres in immune cells taken from the blood.
Telomeres are tiny units of DNA-protein complexes that seal off and protect the ends of chromosomes and act as a biological clock controlling a cell's life. Telomere shortening predicts earlier onset of several major age-related diseases and earlier mortality, and may serve as one index of human longevity.
The researchers compared the length of telomeres in 18 individuals with MDD not currently receiving antidepressant medications to the length of telomeres in 17 healthy controls. Overall, telomeres of the depressed group did not differ from those of the healthy group; however, individuals with nine or more years of untreated chronic depression showed significant telomere shortening, even after accounting for chronological age. The degree of shortening in this subset of the depressed group corresponded to about seven years of "accelerated cell aging."
Telomere shortening also was associated with higher levels of inflammation and oxidative stress in patients, both linked to cell damage and premature aging. Oxidative stress is an imbalance between destructive "free radical" molecules and the body's ability to neutralize them with antioxidants. The authors suggest that telomere shortening in very chronic depression may reflect an individual's cumulative exposure to biochemical stressors that promote cell death and increase the likelihood of physical disease.
"We speculate that telomerase may provide a biological marker for antidepressant responses," added Wolkowitz.
The study has been published online in the journal PLoS One.