Telomere length in psychiatric disorders: Is it more than an ageing marker?

Objectives: Psychiatric and substance-use disorders have been associated with premature biological ageing. Telomere length (TL), considered an ageing marker, has been analysed in psychiatric disorders, and to a lesser extent in substance-use disorders, with recent findings suggesting TL may be related to disease pathology. Methods: We conducted a critical and non-systematic literature search of TL studies published up to June 2016 in psychiatric and substance-use disorders, focussing on studies describing mechanisms, including studies linking telomere biology with genetic factors, stress and mitochondrial alterations (104 studies selected). Results: Patients with major depressive disorder and anxiety appear to have shorter leukocyte telomeres compared to controls. Inconclusive results are found for other psychiatric disorders and for substance-use disorders. This may be due in part to differences in medication treatment and response, as studies suggest that some psychotropic medications may modulate TL. Importantly, some studies establish a relationship between telomere machinery, stress and mitochondria function in psychiatric and substance-use disorders. Conclusions: While further longitudinal studies considering telomere genetics are needed to clarify the cause-effect link between telomeres and mitochondria function in psychiatric and substance-use disorders, the recent findings linking these biological processes suggest that telomeres may be more than ageing markers.