Heredity and personality: A review of concepts, methods, and evidence.

Advances in genetics and genomics have transformed our understanding of personality. The observation that personality traits run in families has prompted extensive study into their heritability and underlying genetic architecture. However, there is a significant discrepancy between psychiatric classifications of personality disorders and genomic findings, suggesting a need to reorient these classifications toward a more dimensional, biologically informed perspective. This article reviews key genetic and genomic findings in personality, focusing on the "Big Five" model, which has proven consistency with genomic research. Twin studies estimate heritability accounts for about 40-50 % of personality traits, while the rest of phenotypic variation is explained by the non-shared environment, which influence personality through epigenetic changes. Genome-wide association studies (GWAS) have identified numerous genetic variants on nearly all chromosomes that influence personality traits, particularly neuroticism. These variants are involved in biological pathways such as neurogenesis and neuronal differentiation. GWAS have also revealed significant genetic correlations between personality traits and major psychiatric disorders, supporting a biological continuum between them. This supports the hypothesis which states that a typical behavioral trait is associated with many genetic variants, each contributing a very small effect. Future research should incorporate epigenetic evidence, study genetic interactions, and expand the diversity of study populations beyond European ancestry to improve the generalizability of findings.