Abstract
BACKGROUND: Several recent studies have investigated the relationship between telomere length and depression with inconsistent results. This meta-analysis examined whether telomere length and depression are associated and explored factors that might affect this association. METHODS: Studies measuring telomere length in subjects with clinically significant unipolar depression were included. A comprehensive search strategy identified studies in PubMed, MEDLINE, PsycINFO, Global Health, The Cochrane Library, and Web of Science. A structured data abstraction form was used and studies were appraised for inclusion or exclusion using a priori conditions. Analyses were conducted using standardized mean differences in a continuous random effects model. RESULTS: Thirty-eight studies (N=34,347) met the inclusion criteria. The association between depression and telomere length was significant, with a Cohen's d effect size of -0.205 (p<0.0001, I(2)=42%). Depression severity significantly associated with telomere length (p=0.03). Trim and fill analysis indicated the presence of publication bias (p=0.003), but that the association remained highly significant after accounting for the bias. Subgroup analysis revealed depression assessment tools, telomere measurement techniques, source tissue and comorbid medical conditions significantly affected the relationship. LIMITATIONS: Other potentially important sub-groups, including antidepressant use, have not been investigated in sufficient detail or number yet and thus were not addressed in this meta-analysis. CONCLUSIONS: There is a negative association between depression and telomere length. Further studies are needed to clarify potential causality underlying this association and to elucidate the biology linking depression and this cellular marker of stress exposure and aging.