An assessment of transmission disequilibrium between quantitative measures of childhood problem behaviors and DRD2/Taql and DRD4/48bp-repeat polymorphisms.

In a pilot study of 120 children with reading disabilities, we assessed the presence of linkage and association between the DRD2/Taql and the DRD4/48bp-repeat polymorphisms and quantitative measures of behavioral problems derived from parental rated Child Behavior Checklist (CBCL) [Achenbach, T. M. (1991). TM Manual for the CBCL 14-18. Burlington, VT: University of Vermont]. Analyses included measures of between-family association, and a test of the presence of linkage and association by a logistic regression-based extension of the Transmission Disequilibrium Test (i.e., the logistic regression quantitative TDT). In between-family association analyses the "Social Problem" scale was weakly associated with the number of risk alleles of DRD2 and DRD4, while the "Withdrawn" scale was related to the number of risk alleles of DRD4 (the 7-repeat and the A1 allele respectively were considered the risk alleles). Logistic regression quantitative TDTs yielded statistically significant evidence in favor of linkage and association between DRD2 and "Social Problems" (Wald chi2 = 4.13, df = 1, p = 0.042, odds ratio = 1.97). A statistical trend in favor of linkage and association was found for "Withdrawn" and DRD4 (Wald chi2 = 2.65, df = 1, p = 0.104, odds ratio =1.44). Although preliminary, these findings are consistent with previous data that suggest a role of the same polymorphism in influencing individual sensitivity to reward and response to social cues and reinforcements in man and animal.