BACKGROUND: Accelerated telomere shortening is associated with stress-related 
cell damage and aging. Patients with depression have been shown to have 
shortened life expectancy and to be associated with multiple age-related 
systemic diseases. Previous studies have examined leukocyte telomere length 
(LTL) in patients with depression, but have shown inconsistent results.
METHODS: We conducted meta-analyses by pooling relevant results strictly from 
all eligible case-control studies for cross-sectional comparison of LTL between 
depressive patients and control subjects (16 studies involving 7207 subjects). 
The effect sizes (shown as Hedges' g) of each individual study were synthesized 
by using a random effects model.
RESULTS: Our analysis revealed telomere length is significantly shorter in 
subjects with depression in comparison to healthy controls (Hedges' g = -0.42, 
p = 1 × 10(-5), corresponding to r = -0.21). Significant heterogeneity among 
studies examining LTL in subjects with depression was found (Q = 116.07, 
df = 16, I(2) = 86.21%, p < 1 × 10(-8)), which can possibly be explained by 
methods used in measuring telomere length (Q = 18.42, df = 2, p = 1 × 10(-4)). 
There was no significant publication bias, nor moderating effect of age, female 
percentage, or illness duration of depression on synthesized results.
CONCLUSIONS: Our results support the hypothesis that depression is associated 
with accelerated cell aging. Future studies are required to clarify whether the 
association is mediated through environmental stress, and whether effective 
treatment can halt cell aging.