View Full Version : Article about ADHD and ODD

Matt S.
10-25-07, 09:12 AM
The purpose of this study was twofold. First, we investigated if teacher ratings on ADHD and ODD are measurement invariant with respect to sex. Secondly, genetic and environmental influences on variation in ADHD and ODD were compared between boys and girls.

Measurement invariance Teacher ratings on ADHD and ODD were found to be measurement invariant with respect to sex. In other words, teacher assessments of these behavior problems relate to the same latent variables in boys and girls. Sex differences in observed scores on ADHD and ODD can, therefore, be interpreted as differences with respect to the latent construct. This supports the contention that the reported sex differences in ADHD and ODD (Gaub and Carlson 1997; Loeber et al. 2000; Maughan et al. 2004) are due to a higher liability for the disorder in boys than girls and not to measurement bias.

Quantitative and qualitative differences in the heritability among boys and girls More than half the variance in ADHD and ODD in boys and girls is attributable to genetic influences. The remaining variance is attributable to unique environmental influences. The magnitude of the influences of genes and environment is the same in boys and girls. However, part of the variance in ADHD and ODD is attributable to different genes in boys and girls. We base this on the fact that the genetic correlation between DZ opposite-sex twins was significantly lower than 0.5, which is the theoretical value (in the absence of assortative mating), if the same genes influence behavior in boys and girls.

We observed a genetic correlation lower than 0.5 in DZ opposite-sex twins for oppositional behavior, cognitive problems-inattention, hyperactivity, and the ADHD index. Few studies have addressed quantitative and qualitative sex differences in heritability estimates from teacher ratings. Saudino et al. (2005) reported qualitative sex differences in heritability of teacher ratings of hyperactive behavior in 7-year-old twins. They did not report any quantitative sex differences, which is in agreement with the current findings. Vierikko et al. (2004) report lower correlations in opposite-sex twins than in same-sex DZ twins of teacher ratings of hyperactivity-impulsivity in 12-year-old twins. However, both genetic and shared environmental effects were found to contribute to the phenotypic variance in these data.

It was not possible to determine if the lower opposite-sex correlations were the result of sex-specific genetic influences or sex-specific shared environmental influences, although the presence of the latter appeared more likely. These findings disagree with the current results in the sense that we did not find any evidence for shared environmental influences. However, both studies suggest that teacher ratings are influenced by partly different etiological factors in boys and girls.The finding of different genetic influences in boys and girls in teacher ratings stands in contrast with results based on parental reports. In parent ratings, qualitative sex differences are not found for attention problems (Rietveld et al. 2004) or ODD (Hudziak et al. 2005).

The different findings in parent and teacher ratings may be explained by the fact that the behavior of children depends on the context in which they are observed. Apparently, inattentive, hyperactive, and oppositional behavior of boys and girls are influenced by partly non-overlapping factors at school, while this is not true for these behaviors at home.The finding of sex-specific genetic variation has implications for gene-finding studies of ADHD and ODD. The fact that the genes which influence the behavior of boys and girls do not completely overlap indicates that some quantitative trait loci may explain variation in boys but not in girls and vice versa. Therefore, the data from boys and girls cannot be collapsed when studying genetic effects in teacher ratings.

In the NTR, teacher data are collected at the ages 7, 10, and 12 years. The sample sizes at the ages 10 and 12 are currently relatively small. In the future, we plan to address the issue of qualitative sex differences in teacher ratings in a longitudinal framework. The results of such a study will reveal if the finding of sex differences in the specific genes that play a role is also present in older children. Another important issue that may be addressed is the MI of ADHD with respect to age.

The results of this study should be interpreted in the light of the following limitations. First, we did not replicate the factor structure of the CTRS-R:S by means of exploratory factor analyses of the 28 items. To take the ordinal nature of the data into account, we used the liability threshold model (Lynch and Walsh 1998). We limited the number of common factors to keep the computational burden manageable. Therefore, we performed CFA, in which we assumed that the items are correctly assigned to the four scales and that cross-loadings are absent. Second, teacher ratings were shown to be measurement invariant with respect to sex, but this finding may not generalize to parent ratings.

The correlations between Conners parent and teacher ratings are small to moderate with a range 0.18–0.52 (Conners 2001). It has been shown that parents and teachers rate partly different aspects of the child’s behavior (Derks et al. in press; Martin et al. 2002). Future studies will reveal if MI is also tenable in parent ratings.Assessment of ADHD and ODD symptoms, through teacher reports on the CTRS-R:S, provides a solid starting point for measuring sex differences in mean scores or in heritabilities. Variation in teacher ratings of children’s problem behavior is mainly influenced by genetic factors. The size of the genetic influences does not depend on the child’s sex, but partly different genes are expressed in boys and girls. Future studies should reveal if these findings generalize to children from different age groups.

10-31-07, 08:45 PM
Gosh MSPEN, where do you find these profile pics?! :)

Matt S.
11-01-07, 08:39 AM
Cute arent they?

11-01-07, 05:28 PM
Cute arent they?
The cat looks exactly like the cat I used to have. It would bit your hand exactly the same way when you tried to pet it.

11-10-07, 11:21 PM
Paragraphs please! I can't see text when it's all one blob. :)

12-22-07, 12:10 AM
Yes! I agree. I tried to read it, but got to the second line and got distracted by rivers and blurs.