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Highlights • Childhood victimization predicted elevated levels of CRP at age 18. • The association between child victimization and CRP levels was specific to females. • Latent genetic influences on CRP levels did not explain the association in females., Objective Childhood victimization is an important risk factor for later immune-related disorders. Previous evidence has demonstrated that childhood victimization is associated with elevated levels of inflammation biomarkers measured decades after exposure. However, it is unclear whether this association is (1) already detectable in young people, (2) different in males and females, and (3) confounded by genetic liability to inflammation. Here we sought to address these questions. Method Participants were 2232 children followed from birth to age 18 years as part of the Environmental Risk (E-Risk) Longitudinal Twin Study. Childhood victimization was measured prospectively from birth to age 12 years. Inflammation was measured through C-reactive protein (CRP) levels in dried blood spots at age 18 years. Latent genetic liability for high inflammation levels was assessed through a twin-based method. Results Greater exposure to childhood victimization was associated with higher CRP levels at age 18 (serum-equivalent means were 0.65 in non-victimized Study members, 0.74 in those exposed to one victimization type, and 0.81 in those exposed to poly-victimization; p = 0.018). However, this association was driven by a significant association in females (serum-equivalent means were 0.75 in non-victimized females, 0.87 in those exposed to one type of victimization, and 1.19 in those exposed to poly-victimization; p = 0.010), while no significant association was observed in males (p = 0.19). Victimized females showed elevated CRP levels independent of latent genetic influence, as well as childhood socioeconomic status, and waist-hip ratio and body temperature at the time of CRP assessment. Conclusion Childhood victimization is associated with elevated CRP levels in young women, independent of latent genetic influences and other key risk factors. These results strengthen causal inference about the effects of childhood victimization on inflammation levels in females by accounting for potential genetic confounding.

Background Previous studies have revealed increased biological ageing amongst major depressive disorder (MDD) patients, as assayed by shorter leukocyte telomere lengths (TL). Stressors such as childhood maltreatment are more common amongst MDD patients, and it has been suggested that this might contribute to shorter TL present amongst patients. However, to our knowledge, no study has yet tested for reverse causality, i.e. whether a genetic predisposition to shorter TL might predispose to MDD or an earlier onset of MDD. Methods This study used a Mendelian randomisation design to investigate if shortened TL might increase risk for recurrent MDD in a relatively large UK sample (1628 MDD cases, 1140 controls). To achieve this, we used a subset of our sample, for which TL data was available, to identify a suitable instrumental variable. We performed single nucleotide polymorphism (SNP) genotyping on rs10936599, a SNP upstream of telomerase RNA component (TERC), and rs2736100, a SNP within telomerase reverse transcriptase (hTERT), and attempted to replicate findings which identified these SNPs as predictors of TL. After which, we performed regressions to test if genetic risk for shortened TL increased risk for MDD, childhood-onset MDD or childhood/adolescent-onset MDD. Results T-carriers of rs10936599 demonstrated shorter TL compared to CC-carriers (p≤0.05; 3% of variance explained) and was subsequently used as our instrumental variable. We found that the T-allele of rs10936599 predicted increased risk for childhood-onset MDD relative to controls (p≤0.05), and increased risk for childhood-onset MDD relative to adult-onset MDD cases (p≤0.001), but rs10936599 did not predict adult-onset MDD risk. Limitations Limitations include a relatively small sample of early-onset cases, and the fact that age-of-onset was ascertained by retrospective recall. Conclusion Genetic predisposition to advanced biological ageing, as assayed using rs10936599, predicted a small, but significant, increased risk for childhood-onset recurrent MDD. Genetic predisposition to advanced biological ageing may be one factor driving previously reported associations (or lack of associations) between shorter TL and MDD. Our results also suggest that the telomerase enzyme may act as a potentially important drug target for the prevention of childhood-onset MDD, at least in a subset of cases. Future studies should attempt to replicate our findings in a larger cohort., Highlights • T-carriers of a single nucleotide polymorphism within the telomerase RNA component gene (rs10936599) predicts shorter telomere lengths, and therefore advanced biological ageing. • T-carriers of rs10936599 are also significantly more likely to be diagnosed with childhood-onset recurrent major depression. • Our study suggests that a genetic predisposition to advanced biological ageing increases risk for early onset recurrent major depression.