Genetic and environmental influences are common to ADHD and reading difficulties but not IQ
30 June 2010
Previous studies have shown there are genes common to attention deficit hyperactivity disorder (ADHD) and reading difficulties (RD). In a study published online at the Journal of Abnormal Child Psychology, researchers from the Institute of Psychiatry (IoP) King’s College London (KCL) have identified that child-specific environmental factors are also common to both conditions and that neither shared genes or child-specific environments are linked to IQ.
Using a large general population sample of 1312 twins aged between seven and ten, the study confirmed previous findings of shared genetic influences. The use of a general population sample allows for a breadth of data without the potential bias associated with clinical samples and studying twins helps disentangle the sharing of genes and environments.
PhD student Yannis Paloyelis, who led the study said: 'As well as shared genetic influences we were very excited to find the addition of child-specific environmental factors common to both ADHD and RD. The absence of a link of either factor to IQ means this co-occurrence is not influenced by IQ as previously thought.'
Principal Investigator Dr Jonna Kuntsi said: 'Understanding the genetic, environmental and behavioural causes common to ADHD and RD is important, as it may have implications for how best to treat both problems more effectively. Further research to identify what the specific environmental factors are could provide targets for future behavioural intervention studies or gene environment interaction studies.'
The study was part of the Study of Activity and Impulsivity Levels in children (SAIL); a project funded by The Wellcome Trust which aims to investigate behaviour in children representative of the general population.
‘The Genetic Association Between ADHD Symptoms and Reading Difficulties: The Role of Inattentiveness and IQ’ Yannis Paloyelis; Fruhling Rijsdijk; Alexis C Wood; Philip Asherson; Jonna Kuntsi, is available online and will be appearing in a forthcoming issue of the Journal of Abnormal Child Psychology. To read the paper in full, please follow the link: http://www.ncbi.nlm.nih.gov/pubmed/20556504.