Depression, telomeres and mitochondrial DNA: between- and within-person associations from a 10-year longitudinal study.

Alterations in cellular aging, indexed by leukocyte telomere length (LTL) and mitochondrial DNA copy number (mtDNAcn), might partly account for the increased health risks in persons with depression. Although some studies indeed found cross-sectional associations of depression with LTL and mtDNAcn, the longitudinal associations remain unclear. This 10-year longitudinal study examined between- and within-person associations of depressive symptoms with LTL and mtDNAcn in a large community sample. Data are from years 15, 20 and 25 follow-up evaluations in 977 subjects from the Coronary Artery Risk Development in Young Adults study. Depressive symptoms (years 15, 20, 25) were assessed with the Center for Epidemiologic Studies Depression (CES-D) scale; LTL (years 15, 20, 25) and mtDNAcn (years 15, 25) were measured in whole blood by quantitative PCR. With mixed-model analyses, we explored between- and within-person associations between CES-D scores and cellular aging markers. Results showed that high levels of depressive symptomatology throughout the 10-year time span was associated with shorter average LTL over 10 years (B=-4.2; P=0.014) after covarying for age, sex, race and education. However, no within-person association was found between depressive symptoms and LTL at each year (B=-0.8; P=0.548). Further, we found no between-person (B=-0.2; P=0.744) or within-person (B=0.4; P=0.497) associations between depressive symptomatology and mtDNAcn. Our results provide evidence for a long-term, between-person relationship of depressive symptoms with LTL, rather than a dynamic and direct within-person relationship. In this study, we found no evidence for an association between depressive symptoms and mtDNAcn.