The genetic and phenotypic relations between childhood attention, aggression, and anxious/depressed behavior: Evidence for developmental difference

Background: Genetic studies of complex behaviors such as ADHD often have not considered the implications of comorbidity when estimating genetic and environmental effects. Some have argued that ADHD with comorbidity may represent different genotypes than uncomplicated ADHD. The purpose of this study was to perform multivariate genetic analyses to determine if there are shared genetic influences between the CBCL syndromes ATT, AGG, and AD. These syndromes have been shown to correlate with DSM ADHD, and ODD. Methods: CBCL data from mothers on 3548 7-year-old, 2591 10-year-old, and 1085 12-year old twin pairs and CBCL data from fathers on 2807 7 year-old, 1987 10-year-old, and 885 12 year-old twin pairs from the Netherlands Twin registry were analyzed. Multivariate genetic analyses were performed using MX in order to determine the shared genetic and phenotypic correlations between ATT, AGG, and A/D on mother and father reports of the same twins when they were 7, 10, and 12 years old. Results: Shared genetic influences were found to range from 60-80% for the relations between AP and AGG, 50-70% between AP and A/D and, 40-60% between AGG and A/D. There are differences in genetic and phenotypic correlations by gender, informant, and age. Discussion: Our results indicate that child psychopathologic syndromes may be influenced by both shared and unique genetic factors. Further, the genetic and phenotypic correlations may be differ by informant, by gender and age. Molecular genetic studies may want to take comorbidity and the above modifying factors into consideration when designing phenotypic strategies for gene finding expeditions.