title: The association of genotype-based inbreeding coefficient with a range of physical and psychological human traits.
abstract: Across animal species, offspring of closely related mates exhibit lower fitness, a phenomenon called inbreeding depression. Inbreeding depression in humans is less well understood because mating between close relatives is generally rare and stigmatised, confounding investigation of its effect on fitness-relevant traits. Recently, the availability of high-density genotype data has enabled quantification of variation in distant inbreeding in 'outbred' human populations, but the low variance of inbreeding detected from genetic data in most outbred populations means large samples are required to test effects, and only a few traits have yet been studied. However, it is likely that isolated populations, or those with a small effective population size, have higher variation in inbreeding and therefore require smaller sample sizes to detect inbreeding effects. With a small effective population size and low immigration, Northern Finland is such a population. We make use of a sample of ∼5,500 'unrelated' individuals in the Northern Finnish Birth Cohort 1966 with known genotypes and measured phenotypes across a range of fitness-relevant physical and psychological traits, including birth length and adult height, body mass index (BMI), waist-to-hip ratio, blood pressure, heart rate, grip strength, educational attainment, income, marital status, handedness, health, and schizotypal features. We find significant associations in the predicted direction between individuals' inbreeding coefficient (measured by proportion of the genome in runs of homozygosity) and eight of the 18 traits investigated, significantly more than the one or two expected by chance. These results are consistent with inbreeding depression effects on a range of human traits, but further research is needed to replicate and test alternative explanations for these effects.
authors: School of Psychology, University of Queensland, Brisbane, Queensland, Australia; Department of Biological Psychology, VU University Amsterdam, Amsterdam, The Netherlands.
authors: Karin J H
authors: KJ
authors: Verweij
authors: Department of Biological Psychology, VU University Amsterdam, Amsterdam, The Netherlands.
authors: Abdel
authors: A
authors: Abdellaoui
authors: Department of Psychiatry, University of Oulu and Oulu University Hospital, Oulu, Finland.
authors: Juha
authors: J
authors: Veijola
authors: Institute of Health Sciences, University of Oulu, Oulu, Finland; Biocenter Oulu, University of Oulu, Finland.
authors: Sylvain
authors: S
authors: Sebert
authors: Institute of Health Sciences, University of Oulu, Oulu, Finland.
authors: Markku
authors: M
authors: Koiranen
authors: Department of Psychology and Neuroscience, University of Colorado, Boulder, Colorado, United States of America; Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado, United States of America.
authors: Matthew C
authors: MC
authors: Keller
authors: Institute of Health Sciences, University of Oulu, Oulu, Finland; Biocenter Oulu, University of Oulu, Finland; Department of Epidemiology and Biostatistics, MRC Health Protection Agency (HPA) Centre for Environment and Health, School of Public Health, Imperial College London, United Kingdom; Unit of Primary Care, Oulu University Hospital, Oulu, Finland; 10 Department of Children and Young People and Families, National Institute for Health and Welfare, Oulu, Finland.
authors: Marjo-Riitta
authors: MR
authors: Järvelin
authors: School of Psychology, University of Queensland, Brisbane, Queensland, Australia; Genetic Epidemiology, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.
authors: Brendan P
authors: BP
authors: Zietsch
mesh_terms: D000328:Adult; D000886:Anthropometry; D003241:Consanguinity; D005260:Female; D005387:Finland; D056084:Genetic Fitness / Q000502:physiology*; D005828:Genetics, Population; D005838:Genotype; D006720:Homozygote; D006801:Humans; D008297:Male; D008603:Mental Health; D010641:Phenotype; D012098:Reproduction