Heritability of attention problems in children: I. cross‐sectional results from a study of twins, age 3–12 years

Abstract

Multiple twin studies of attention problems (AP) from the Child Behavior Checklist or ADHD from the DSM criteria have reported on the genetic and environmental influences on these behaviors. The majority of these have studied AP and ADHD symptoms in twin samples combined across wide age spans, combined rater information and both genders. Thus, it is possible that the results are complicated by developmental, informant, and gender differences. The purpose of this study was to assess for the genetic and environmental contributions to overactive behavior (a syndrome highly related to AP in 7-, 10-, and 12-years olds) in 3-years olds (3,671 twin pairs), and attention problems in 7-(3,373 twin pairs), 10-(2,485 twin pairs), and 12-years olds (1,305 twin pairs) while controlling for developmental, gender and rater contrast contributions. Using a crosssectional twin design, contributions from genetic additive, genetic dominance, unique environmental and rater contrast effects were estimated for CBCL maternal reports. We found that genetic influences on overactive behavior and attention problems are high across an age span that covers preschool and elementary school age. Although girls display less problem behavior compared to boys, heritability estimates were found equal for both genders at each age. Environmental experiences that are unique to the individual accounted for the remaining influence. At the age of 3 years, a rater contrast effect was detected. We hypothesize that the contrast effect represents a maternal rater bias effect that is dependent on the age of the twins. The implications of these findings are discussed with reference to the clinical setting and in the context of future research. ß

Phenotypic and measurement influences on heritability estimates in childhood ADHD

“…If these contrast effects are not accounted for in the analysis, mother ratings will result in lower DZ concordance rates and successively in an overestimation of heritability. Rater contrast effects were described for the Rutter-A scale, the DBRS, parental interview data obtained by the CAPA (Table 1) and for the CBCL at age 3 only but not for children aged 7-12 years old [47,89,90].…”

“…If MZ variance is smaller than DZ variance, and DZ correlation is very low compared to MZ correlation, this is indicative of a rater contrast effect. Structural equation models allow differentiating between dominant genetic and rater effects [89,91]. Heritability in the broad sense refers to additive and dominant genetic effects together; heritability in the narrow sense refers only to additive genetic effects.…”

Attention problems, inhibitory control, and intelligence index overlapping genetic factors: A study in 9-, 12-, and 18-year-old twins.

“…Male and female data were combined in the MZ twin, DZ twin, and twin-sibling groups in the genetic analyses because there is no evidence for sex differences in heritability for ADHD (Derks et al, 2004;Derks et al, 2007;Hudziak et al, 2005;Rietveld et al, 2003) and IQ (Bartels, Rietveld, van Baal & Boomsma, 2002), and the power to detect sex differences in genetic influences in the independent samples was limited (Polderman, Stins, et al, 2006). MZ twins share all their genes whereas DZ twins and siblings share on average half of their segregating genes.…”

“…and Rietveld et al (2003) demonstrated that genetic influences on AP are equally important for boys and girls. AP are often assessed with behavior questionnaires that can be completed by different informants.…”

Non-additive and Additive Genetic Effects on Extraversion in 3314 Dutch Adolescent Twins and Their Parents

“…Studies in children, however, have had to rely on informants who rate the behavior of both twins. In this design, non-additive genetic influences are difficult to distinguish from rater contrast effect, in which an informant magnifies differences in DZ twins to a larger extent than in MZ twins (Rietveld et al 2003). Many studies of infants and toddlers show heritability estimates for extraversion and its correlates from approximately 35-47% across twin and adoption designs (Dilalla and Jones 2000).…”