A Twin Study Of Behavior Problems In Children And Adolescents Aged 10-16 Years

Objective: To investigate the prevalence of behavior problems in twins aged 10-16 years; to estimate genetic, shared environmental, and nonshared environmental contributions to children and adolescents' behavior problems; to test whether gene and family cohesion interplay in behavior problems; and to provide theoretical foundation for environmental intervention in children and adolescents' behavior problems.Method: The sixty-four twin pairs aged 10-16 years in Chengdu city participated in this study after multi-stage sampling. The Child Behavior Checklist (CBCL) rated by twin parents was used to assess behavior problems and the cohesion subscale of the Family Environment Scale (FES-CV) was used to assess family cohesion. The prevalence rate of behavior problems in twins and genetic and environmental influences on behavior problems of children and adolescents were estimated, and gene-family cohesion interaction analyse was conducted.Results: (1) The prevalence rate of behavior problems in twins aged 10-16 years was 6.25%, lower than nationwide epidemiologic data (P＜0.05). No difference was found in prevalence rate of behavior problems between different sex and zygosity (P＞0.1). (2) Behavior problems of twin children and adolescents consisted mostly of social problems, accounting for 38.46% of totality. The prevalence rate of social problems showed no difference between monozygotic (MZ) and dizygotic (DZ) twins (P＞0.05). (3) For behavior problems of children and adolescents at age 10 to 16 years, genetic (h~2), shared (c~2), and nonshared environmental (e~2) factors explained about 33%, 57%, and 10% of the variance, which indicated significant environmental influences on behavior problems, especially shared environment, despite genetic influences were detected too. (4) Genetic, shared, and nonshared environmental influences explained 66/64%, 18/24%, and 16/12% of the variance of Internalizing/Externalizing Problems in children aged 10-11 years. (5) Genetic, shared, and nonshared environmental influences on Internalizing/ Externalizing Problems accounted for 65/67%, 16/20%, and 19/3% of the variance in adolescents aged 12-16 years. (6) h~2, c~2, and e~2 of behavior problems were 0.18, 0.73, and 0.09 respectively in male children and adolescents. (7) h~2, c~2, and e~2 of behavior problems were 0.39, 0.50, and 0.11 respectively in female children and adolescents. (8) The average of twin family cohesion was 6.66±1.91, lower than Chinese norm (P＜0.001). No difference was found in family cohesion between different zygosity (P＞0.05). (9) For behavior problems of children and adolescents, genetic influences estimates were 0.88 and 0.75 respectively in family environment of low and high level cohesion, which showed heritability of behavior problems in low cohesive family environment exceeded that in high cohesive family environment. Conclusions: (1) The prevalence rate of behavior problems in twins aged 10-16 years was lower than that of nontwins. (2) Social problems are the most common behavior problems in twin children and adolescents. (3) Genetic and environmental influences both contributed to behavior problems of children and adolescents, but environmental factors were more influential, especially shared environmental influences. (4) Genetic influences remained relatively constant on Internalizing Problems and increased on Externalizing Problems with age. Shared environmental influences on Internalizing/ Externalizing Problems both remained constant at different age. (5) Shared environmental influences on behavior problems in children and adolescents of different sex were significant. But shared environmental effects were more important in male, and behavior problems in female were influenced by genetic factors more than those in male. (6) The family cohesion of twins was lower than that of nontwins. (7) For behavior problems of children and adolescents, genetic factors and family cohesion maybe interacted, which indicated that there were more chances for high-risk genotype to express in low cohesive family (high-risk environmental exposure), and genetic risk was decreased in high cohesive family (low-risk environmental exposure). This study provided theoretical foundation for prevention and intervention in behavior problems of children and adolescents.