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Objective: Our study aims to estimate the proportion of the phenotypic variance of Neuroticism and its facet scales that can be attributed to common single-nucleotide polymorphisms (SNPs) in two adult populations from Estonia (EGCUT; N = 3,292) and the Netherlands (Lifelines; N = 13,383).Method: Genomic-relatedness-matrix restricted maximum likelihood (GREML) using genome-wide complex trait analysis (GCTA) software was employed. To build upon previous research, we used self- and informant reports of the 30-facet NEO personality inventories and analyzed both the usual sum scores and the residual facet scores of Neuroticism.Results: In the EGCUT cohort, the proportion of phenotypic variance explained by the additive effects of common genetic variants in self- and informant-reported Neuroticism domain scores was 15.2% (p = .070, SE = .11) and 6.2% (p = .293, SE = .12), respectively. The SNP-based heritability estimates at the level of Neuroticism facet scales differed greatly across cohorts and modes of measurement but were generally higher (a) for self- than for informant reports, and (b) for sum than for residual scores.Conclusions: Our findings indicate that a large proportion of the heritability of Neuroticism is not captured by additive genetic effects of common SNPs, with some evidence for Gene × Environment interaction across cohorts. [ABSTRACT FROM AUTHOR]

Evidence suggests that developing and maintaining an effective immune system may be costly and that an organism has to make a trade-off between immune function and other fitness-enhancing traits. To test for a trade-off between growth and immune function we carried out a meta-analysis of data from lines of poultry that had been divergently selected for either growth (body mass) or an aspect of immune function. This is relevant to our understanding of the evolution of immune function, but also because the increased prevalence of antibiotic-resistant bacteria and calls to restrict the use of antibiotics in the agricultural industry has made immune function of livestock an important theme. Has the selection of animals for rapid growth unintentionally resulted in reduced immune function? The lines selected for increased growth all showed a strong and significant decrease in immune function (standard difference in means = 0·8; P < 0·001). No difference was found between the effects on cellular or humoral immunity, although there were few data on cellular immunity, and hence this deserves more study. However, in the lines selected for immune function the effect on growth was heterogeneous and overall it was close to zero. Testing for publication bias revealed that the effect of selection for body mass on immune function was robust. However, there was considerable heterogeneity in both body mass and immune function data. The heterogeneity in the growth-selected lines cannot be accounted for by gender or species: the only turkey line had an effect size between that of the two chicken lines. In conclusion, we found that selection for growth does indeed compromise immune function, but selection for immune function did not consistently affect growth. This is in agreement with the supposition that the costs of growth are large relative to the costs of immune function, and on a practical level this suggests that it may be possible to breed animals for increased growth without loss of immune function. [ABSTRACT FROM AUTHOR]

Background and Aims: Cannabis is one of the most commonly used substances among adolescents and young adults. Earlier age at cannabis initiation is linked to adverse life outcomes, including multi-substance use and dependence. This study estimated the heritability of age at first cannabis use and identified associations with genetic variants., Methods: A twin-based heritability analysis using 8055 twins from three cohorts was performed. We then carried out a genome-wide association meta-analysis of age at first cannabis use in a discovery sample of 24 953 individuals from nine European, North American and Australian cohorts, and a replication sample of 3735 individuals., Results: The twin-based heritability for age at first cannabis use was 38% [95% confidence interval (CI) = 19-60%]. Shared and unique environmental factors explained 39% (95% CI = 20-56%) and 22% (95% CI = 16-29%). The genome-wide association meta-analysis identified five single nucleotide polymorphisms (SNPs) on chromosome 16 within the calcium-transporting ATPase gene (ATP2C2) at P < 5E-08. All five SNPs are in high linkage disequilibrium (LD) (r 2  > 0.8), with the strongest association at the intronic variant rs1574587 (P = 4.09E-09). Gene-based tests of association identified the ATP2C2 gene on 16q24.1 (P = 1.33e-06). Although the five SNPs and ATP2C2 did not replicate, ATP2C2 has been associated with cocaine dependence in a previous study. ATP2B2, which is a member of the same calcium signalling pathway, has been associated previously with opioid dependence. SNP-based heritability for age at first cannabis use was non-significant., Conclusion: Age at cannabis initiation appears to be moderately heritable in western countries, and individual differences in onset can be explained by separate but correlated genetic liabilities. The significant association between age of initiation and ATP2C2 is consistent with the role of calcium signalling mechanisms in substance use disorders., (© 2018 Society for the Study of Addiction.)