Does telomere length mediate associations between inbreeding and increased risk for bipolar I disorder and schizophrenia?

We have recently found that consanguinity is a risk factor for bipolar I disorder (BP1) and schizophrenia (SZ) in Egypt. Inbreeding has been associated with increased cellular stress and impaired physiological function in plants and animals. Previous studies have reported that telomere length (TL), an index of oxidative stress and cellular senescence is significantly reduced among patients with SZ or mood disorders compared with control individuals. Hence we evaluated TL as a possible mediator of the observed association between consanguinity and BP1/SZ risk. Patients with BP1 (n = 108), or SZ (n = 60) were compared with screened adult controls in separate experiments. TL was estimated using a quantitative PCR (qPCR) based assay. The inbreeding coefficient/consanguinity rate was estimated in two ways: using 64 DNA polymorphisms ('DNA-based' rate); and from family history data ('self report'). Significant correlation between TL and DNA based inbreeding was not observed overall, though suggestive trends were present among the SZ cases. No significant case-control differences in TL were found after controlling for demographic variables. In conclusion, reduced TL may not explain a significant proportion of observed associations between consanguinity and risk for BP1/SZ.