Relationship of the functional polymorphism of dopamine D4 receptor gene with behavioral problems in school-age twins

Abstract

Objective To investigate the correlation and characteristic of the functional polymorphism of the dopamine D4 receptor gene on the behavioral problems in school-age twins. Method The behavioral problems were assessed among a total of 147 twin pairs aged 6-12 years with the Achenbach Child Behavior Checklist (CBCL). The DRD4 gene polymorphism was applied for different types with polymerase chain reaction. The generalized estimating equations model was used to analyze the effect of DRD4 gene polymorphism and the interaction of DRD4 gene polymorphism with children age, gender, monozygotic/dizygotic on twins’ behavioral problems. Results (1) School-age children’s anxiety/depression, withdrawn, thought problems, attention problems, social problems, delinquent problems, aggressive behavior and total variance mainly were correlated with DRD4 gene polymorphism (P<0.05), and physical discomfort might be related with DRD4 gene polymorphism (P=0.067). Except social problems, the detection rate of behavioral problems of the twins with 4/6 genotype (Gene type carrying 5 or more repeated sequences) of DRD4 gene (6.25%-21.25%)was higher than those with other genotypes (0-14.74%). (2) Withdrawal was related to children age (χ2=4.348, P<0.05), and twins aged 6-10 might lead to withdrawal. (3) The interaction of DRD4 gene polymorphism and children age had a significant effect on withdrawal (χ2=4.348, P<0.05) and physical discomfort(χ2 =5.189, P<0.05), and the elder age (11-12 years) children had a certainly protective effect on the withdrawal and physical discomfort with 4/6 genotype in twins.The detection rates were 3.54% and 2.65% in the younger-age (6-10 years) twins, while all 0 in the elder-age (11-12 years) for the withdrawal and the physical discomfort respectively. Conclusions The DRD4 gene polymorphism may be correlated with behavioral problems in school-age twins. The interaction of DRD4 polymorphism and children age had a significantly effect on withdrawal and physical discomfort. Key words: DRD4 gene; School-age children; Twins; Behavioral problems