It is a well known finding that autism, a neurodevelopmental condition affecting social interaction, communication, and patterns of behaviour and interest, is more common in boys than girls. Yet few studies have asked why this is.
A new study published in Proceedings of the National Academy of Sciences, a collaboration between the GEL lab director Dr Angelica Ronald, GEL lab collaborator Dr Elise Robinson, and members of the Child and Adolescent Twin Study of Sweden team, investigated the extent to which male preponderance in autistic impairments might be explained by a female protective effect. As autistic behaviours often run in families, a female protective effect would predict that siblings of girls with high autistic behaviour scores would carry more risk factors than the siblings of boys with high autistic behaviour scores.
The researchers looked for this pattern in two large, independent cohorts of non-identical twins: 3,842 12-year-old twin pairs in the UK-based Twins Early Development Study, and 6,040 9- and 12-year-old twin pairs in the Child and Adolescent Twin Study of Sweden. Autistic behaviours of all study participants were measured, and the pairs in which one twin (the proband) scored in the top 10% of the autistic impairment distribution were compared. In both study populations, siblings of female probands displayed significantly greater average impairments than the siblings of male probands. The findings provide support for the existence of a possible female protective effect against familial souces of autistic behavioural impairment.
You can read more about the study here, as well as a commentary on the study.
Reference
Robinson, E.B., Lichtenstein, P., Anckarsater, H., Happe, F., & Ronald, A. (2013). Examining and interpreting the female protective effect against autistic behavior. Proceedings of the National Academy of Sciences of the United States of America, online first publication.
Many recent studies suggest that autism, a neurodevelopmental condition characterised by atypicalities in social interaction, communication, and patterns of behaviour and interest, regularly co-occurs with attention deficit/hyperactivity disorder (ADHD). ADHD is also a neurodevelopmental condition, marked by excessive levels of hyperactive and impulsive behaviours and/or inattentiveness.
There have been several cross-sectional twin studies on the relationship between traits characteristic of autism and ADHD, meaning that the relationship was explored at a single age. These studies have provided evidence that similar genes might underlie these conditions and their characteristic traits.
Despite autism and ADHD being developmental conditions, few studies have used data collected at multiple ages (a longitudinal design). GEL lab members Mark Taylor and Dr Angelica Ronald, working with GEL lab collaborator Prof Tony Charman and a team of researchers involved in the Twins Early Development Study, used a longitudinal twin design to explore how traits associated with autism and ADHD might influence one another across development. The results, published in Psychological Medicine, suggested that while earlier traits of autism influenced later traits of ADHD, earlier of traits of ADHD more strongly influenced later traits of autism. In particular, earlier ADHD-like behaviours influenced later communication atypicalities characteristic of autism. These results highlight the useful insights that longitudinal research might provide in understanding the relationship between co-occurring autism and ADHD across development.
You can read more about the study here.
Reference
Taylor, M.J., Charman, T., Robinson, E.B., Plomin, R., Happe, F., Asherson, P., & Ronald, A. (2012). Developmental associations between traits of autism spectrum disorder and attention deficit hyperactivity disorder: A genetically-informative, longitudinal twin study. Psychological Medicine, online first.
Three GEL lab PhD students, Kostas Papageorgiou, Dominika Sieradzka, and Mark Taylor, all travelled to Boulder, Colorado in the United States to attend the International Workshop on Statistical Genetic Methods for Human Complex Traits in March 2013.
The workshop runs once every two years. A group of renowned researchers in genetics come together to teach the latest methods used to examine the genetics of complex human behaviours, such as cognitive ability, personality, and psychological conditions. Topics included genomewide association studies, genomewide complex trait analysis, and sequencing.
The course was an excellent opportunity to keep up to date with all the lates developments in molecular genetic methods, and to meet other individuals from different institutions working in the field.
And, of course, the team were also able to enjoy the local scenary and see the Rocky Mountains in the snow!