Interactive effects of genetic and environmental factors in the development of personality

1999 Fiscal Year Final Research Report Summary

• Project/Area Number: 09671005
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Psychiatric science
• Research Institution: Keio University
• Principal Investigator: ONO Yutaka Department of Neuropsychiatry, 医学部, 専任講師 (70138098)
• Co-Investigator(Kenkyū-buntansha): SHIRAHASE Joichiro Department of Neuropsychiatry, School of Medicine ; assistant, 医学部・精神神経科, 助手 (40206298) ; KANDA Shigenobu Department of Psychiatry, Yamanashi Medical University ; professor, 医学部・精神神経学講座, 教授 (50195187) ; ANDO Juko Faculty of Letters, Keio University ; assistant professor, 文学部, 助教授 (30193105) ; YOSHIMERA Kimio Cancer Information and Epidemiology Division, National Cancer Center Research Institute ; research fellow, 研究員 (10265910)
• Project Period (FY): 1997 – 1999
• Keywords: behavior / genetics / genetic / NEO-PI-R / environment / resring attitude / twin personality / TCI

Research Abstract

The dimensional approaches have been thought to describe the fundamental dimensions that underlie the entire domain of normal and Pathological personality functions. Among many different models proposed to identify such personality dimensions, the five factor model model and the seven factor model have been the most widely accepted and investigated. We tested these two models of personality structure in a sample of Japanese twins, to clarify the contributions of genetic and environment The NEO-PI-R and Temperament and Character Inventory (TCI) were administered to 251 twin pairs, ranging in age from 15 to 27years of age. Both NEO-PI-R and TCI are 240-item questionnaires which was developed to assess the five and seven dimensions of personality respectively Regarding the five factormodel, univariate genetic analysis showed that the AE model in which phenotypic covanances are explained only by additive genetic (A) and nonshared environment (E) is still a plausible model, and that the rel ative proportion of genetic influence was comparable to that reported by Loehlin (1992). Multivariate genetic analysis of the Japanese data suggested/reveaiedthat-the five factors are genetically dependent on each other and one common genetic factor mediates their interdependence. Previous studies have assumed that they are phenotypicall independent and robust Although there are sampling biases in the present study, it is noteworthy that the results for all five factors depicted by the NEO-PI-R were comparable to those reported by Western researchers, and the genetic structure of the five-factor model is complex. Regarding seven factor model, among four temperament dimensions (novelty seeking(NS), harm avoidance(HA), reward dependence(RD). Persistence(PS), NS and PS showed significant additive genetic contributions and no shared environmental effect, supporting the original theoreticals assumption. HA and RD could be explained by either genetic or shared environmental factors. Among three character dimensions, only cooperativeness (CO) could explained exclusive by environment (shared and nonshared). Self-directedness (SD) and Self-transcendence (ST) seemed to be affected by either genetic or shared environment factor. Multivariate genetic analysis indicated that NS, HA, and RD were genetically independent as the theory predicts, and genetic components of PS and SD (under the genetic model) were entirely derived from those of temperament dimensions. Phenotypic correlationbetween NS and HA could be explained by nonshared environmental overlap. Under the environmental model, SD and CO had their own shared environmental origins and ST was affected by those two shared environmental components. Under the genetic model, SD overlapped entirely with genetic components of three temperament dimensions, whereas ST had its own genetic component.