Autistic and schizophrenic people and have been shown to have certain chromosomal defects called copy number variants (CNVs). This study was undertaken to determine if certain CNVs were the genetic cause for attention-deficit hyperactivity disorder (ADHD) and whether these CNVs were related to those associated with autism and schizophrenia. Results suggested that it was indeed true. On analysis, it was also observed that there were more genetic defects when ADHD and mental disability presented together.
ADHD is a childhood disease that makes children inattentive, careless and physically hyperactive. This disease affects around 2 percent of children and most of those affected continue to deteriorate as they age. Though ADHD is transmitted genetically, the specific genes responsible for ADHD have not been identified to date. This comparative study conducted at Cardiff University in Wales suggested various complex genetic abnormalities associated with the origin of the disease. It also proved that the cause for ADHD is definitely more than the social environment influencing the child.
* 410 children of British origin aged between 15 and 17 years and diagnosed with ADHD were chosen from children’s clinics for this study. Samples of their blood or saliva were taken.
* The genetic components of these children were compared with computer-stored genetic data of 1,156 British individuals.
* Genetic data was analyzed using specific tests that could read and compare enormous quantity of DNA rapidly, yet accurately. CNVs that corresponded to regions of deleted or added genetic information were looked for. The results were statistically analyzed.
* Large and highly significant chromosomal abnormalities in the form of deletions or duplications were found in children with ADHD when compared with the normal participants in the study.
* Irrespective of the type of sample (blood or saliva) collected from the children, there was no significant difference in the detection of these chromosomal defects i.e. CNVs.
* The CNVs were more than two times higher if the ADHD patients had associated mental disability.
* The areas of chromosomal defects in ADHD were similar to those in diseases like autism and schizophrenia.
This study involved only a particular group of children. They were all of British origin and it is known that a genetic disease may have different outcomes depending on the race, sex and build of each individual. An important factor in diseases affecting children is the influence of the environment. Better environmental enrichment could reduce the severity of certain diseases. In this study, however, environmental factors were not considered.
This study has given new insights into the mechanism of the genetic cause of ADHD. It indicated that ADHD is not a mere socially disruptive condition but a medical disease. New and better methods to assess these patients are currently available. More research in this area could help understand the disease better. Results from this study suggest that children with ADHD and a mental disability should be taken to clinical geneticists for a complete assessment of the condition. This would aid in understanding the condition and severity of the disease.
For More Information:
Genetic Basis of Attention-Deficit Hyperactivity Disorder
Publication Journal: The Lancet, September 2010
By Nigel M. Williams, Irina Zaharieva; Cardiff University, UK