The report is here - Does depression contribute to the aging process?
Stress has numerous detrimental effects on the human body. Many of these effects are acutely felt by the sufferer, but many more go 'unseen', one of which is shortening of telomere length.
Telomeres are protective caps on the ends of chromosomes and are indicators of aging, as they naturally shorten over time. However, telomeres are also highly susceptible to stress and depression, both of which have repeatedly been linked with premature telomere shortening.
The human stress response is regulated by the hypothalamic-pituitary-adrenal axis, or HPA axis. This axis controls the body's levels of cortisol, the primary stress hormone, and it generally does not function normally in individuals with depression- and stress-related illnesses.