The sex ratios of families with a neurodevelopmentally disordered child

Neural Mechanisms of Language-Based Learning Impairments: Insights from Human Populations and Animal Models

The acquisition of speech perception and consequent expression of language represent fundamental aspects of human functioning. Yet roughly 7% to 8% of children who are otherwise healthy and of normal intelligence exhibit unexplained delays and impairments in acquiring these skills. Ongoing research has revealed several key features of language disability that may pro-vide more direct insight into underlying anomalous neural functioning. For example, evidence supports a strong association between basic defects in processing rapidly changing acoustic information and emergent disruptions in speech perception, as well as cascading effects on other forms of language development (including reading). Considerable neurobiological research has thus focused on developmental factors that might deleteriously influence rapid sensory processing. Additional research focuses on mechanisms of neural plasticity, including how such brains might be “retrained” for improved processing of language. These and related findings from human clinical studies, electrophysiological studies, neuroimaging studies, and animal models are reviewed.

Further evidence that some male-based neurodevelopmental disorders are associated with high intrauterine testosterone concentrations

It has been suggested that reading disability (RD), autism spectrum disorder (ASD), and attention-deficit-hyperactivity disorder (ADHD) share a measure of genetic overlap. They also share some epidemiological features, and have all been suspected of multifactorial (genetic and environmental) threshold origins. It has also been hypothesized that ASD, pervasive developmental disorder - not otherwise specified, and ADHD are partially caused by high maternal intrauterine testosterone levels. Here I offer a new method of testing this latter hypothesis on some of these disorders (RD, ADHD, and ASD). All these disorders occur more commonly in males. If the intrauterine testosterone hypothesis was correct, then probands should have a statistically significant excess of brothers among their siblings. Data are adduced here to test this. When treated as individual disorders, the data are significant only in the case of RD. However, the data are highly significant when pooled as RD + ADHD or RD + ADHD + ASD. Taken alone, the data on ASD are not significant. These results suggest that: (1) taxonomically, RD and ADHD are moresimilar to one another than either is to ASD; and (2) probands in the pooled samples have a very highly significant excess of brothers. This result stands in need of explanation. Provisionally, the data may be interpreted as suggesting that RD may be caused by high intrauterine testosterone levels, and confirming the hypothesis that ADHD is partially caused by high intrauterine testosterone.

Male vulnerability to reading disability is not likely to be a myth: a call for new data

Whether boys are more vulnerable than girls to reading disabilities (RD) is controversial. We review studies that were designed to minimize ascertainment bias in the selection of individuals with RD. These include population-based studies that identified children with RD by objective, unbiased methods and studies that examined the gender ratios among the affected relatives of those diagnosed with RD. We conclude that even when ascertainment biases are minimized, there is still a significant preponderance of boys with RD, although the gender ratio of the affected relatives of those with RD manifests the weakest male bias. Furthermore, we demonstrate that potentially confounding factors such as attentional or neurological problems, race, IQ, and severity of RD cannot account for the observed gender bias. We end with a clarion call to future researchers to (a) consider analyzing gender differences by means of more than one definition of RD, (b) compare gender ratios when boys and girls are ranked against the performance of their own gender as opposed to an average across genders, and (c) report group differences in variability and effect sizes of obtained gender ratios.

Sibling sex ratio of boys with gender identity disorder

Sibling sex ratio (the ratio of brothers to sisters) was calculated for 444 boys with gender identity disorder (or with behaviors consistent with this diagnosis). The probands were ascertained from several researchers with expertise with this disorder and from the English language case report literature between 1938 and 1995. Among the probands with at least one sibling (N = 333), the results showed that boys with gender identity disorder had a significant excess of brothers to sisters, 131.1:100, when compared with the expected secondary sex ratio of 106:100. The excess of brothers replicated a previous study by Blanchard, Zucker, Bradley, and Hume (1995), in which the sibling sex ratio was 140.6:100. Further analyses showed that the probands were born later relative to their brothers than they were relative to their sisters. These findings are amenable to several psychosocial and biological explanations, which require further investigation.

A re-examination of the sex ratios of families with a neurodevelopmentally disordered child

It has been claimed that mothers with certain hormonal imbalances and/or immunological disorders are more likely to give birth to male than female children and that they are more likely to give birth to a neurodevelopmentally disordered (ND) child. Liederman and Flannery (1995) reported that the sex ratio of families with an index ND child did not significantly differ from the sex ratio of families without an index ND child. The data were derived from the National Collaborative Perinatal Project (NCPP). James (in the current issue) challenged us to reconsider the standard against which we judged the sex ratio of siblings of ND children, since the 1.10 sex ratio that we obtained for the siblings of non-ND children is much higher than the sex ratio of children born during that period according to the U.S. Census Bureau. In the current paper, the NCPP data were reexamined and it was demonstrated that the high sex ratio of siblings in our non-ND sample was not due to various retention or recruitment biases. Thus, we suggest that use of the sex ratio of siblings of non-ND children was the proper standard against which to judge the sex ratio of ND families, and that our data provide no evidence to support the notion that these families are male biased.