Table 1: Overview of studies: telomere length and depression.

First author, dateType of study, total Method TL shorter in participants with MDD or MDE or depression symptomsMean difference in TL, approx. years of accelerated agingOther findingsStudy
limitations

Studies of participants with MDD

Simon, 2006 [46]Cross-section, LTL-Southern blotYes*660 bps, ~10 yrsa, b, c
Lung, 2007 [47]Cross-section, LTL-Southern blotYes*96 bps, ~2 yrsa, b, c
Hartmann, 2010 [45]Cross-section, LTL-Southern blotYes*350 bps, ~5 yrsa, b, c
Hoen, 2011 [44]Cross-section, PBMCs-qPCRYes**97 bps, ~2 yrsc
Wolkowitz, 2011 [18]Cross-section, LTL-qPCRYes*280, ~7 yrsIL6 inversely correlated with TL in depressed pts*b
Malan, 2011 [48]Cross-section, LTL-qPCRBTL not associated with development of MDD in 3 monthsTL associated with development of PTSD**b, d
Wolkowitz, 2012 [49]Longitudinal, PBMCs TRAPeze assay for TAYes* (reported in Wolkowitz 2011 [18])280, ~7 yrsBTA elevated in depression* and high stress*; lower BTA predicted better response to antidepressant*; no correlation between TA, IL6, CRP, and TL
Wikgren, 2012 [50]Cross-section, LTL-qPCRYes*277 bps, ~4 yrsTL shorter and CRP higher in MDD with low post-DST cortisol levels*a, c

Studies of participants with history of MDEs or self-reported depression symptoms

Elvsashagen, 2011 [51]Cross-section, PBMCs-qFISHYes**552 bps, ~9 yrsb, c, e
Shaffer, 2012 [52]Cross-section, LTL-qPCRNoa, b, c, e
Hoen, 2013 [53]Longitudinal, LTL-qPCRNoAnxiety disorder associated with shorter TL over time**e, f

: P < 0.05; **trend: P < 0.10.
LTL: leukocyte telomere length; BTL: baseline telomere length; BTA: baseline telomerase activity; DST: dexamethasone suppression test; qPCR: quantitative polymerase chain reaction; qFISH: quantitative fluorescence in situ hybridization.
aUnclear if controls actually screened for MDD or controls answered in negative regarding previous diagnosis of MDD.
bFactors potentially affecting TL not evaluated/reported (stress, BMI, smoking status, physical activity, anti-inflammatory medications).
cHomogeneous group or ethnicity/races unreported.
dTesting unidirectional hypothesis (telomere length leads to development of depression).
eNo clinical diagnosis of depression (self-report of previous MDE or depression symptoms).
fBiomarkers measured at different time point than depression diagnosis.