Almost nine percent of American children will be diagnosed with ADHD at some point, according to the Centers for Disease Control and Prevention, but that diagnosis is not usually made until kids are around age seven or older. A new study has suggested that genetic testing could help identify children with ADHD sooner, and potentially provide support before complications occur. While it's been thought that the genetics of ADHD would be complex and difficult to elucidate, a this research has suggested that as many as half of ADHD cases can be revealed by looking for certain single-base pair changes in genes. The findings have been reported in JAMA Pediatrics.
"Earlier diagnosis would allow us to support the child and family before secondary problems arise, such as academic problems, social rejection, and stress on the family," said first study author Anne Arnett, PhD, a researcher in the Division of Developmental Medicine at Boston Children's Hospital.
In this study, the researchers examined whole-genome sequencing data obtained from 77 kids who had been diagnosed with ADHD and were between the ages of 6 and 18. Additional data was also included from siblings and parents of the ADHD patients, who both had or didn't have ADHD.
Children who had also been diagnosed with autism spectrum disorder, serious intellectual disabilities, or known genetic diseases were excluded from the study to make the results more specific to ADHD.
"We started finding genetic diagnoses in the children pretty quickly," noted senior study author Ryan Doan, PhD, of the Division of Genetics and Genomics at Boston Children's. "That was a little surprising."
There were forty families, or about 52 percent of study participants who carried genetic variants that were probably causing ADHD. While some of these variants had been inherited, some gene changes were not found in other family members.
The study also showed that some of these causative variants were present in genes that are related to methylation, or the chemical modification of other genes. Many causative variants were present in genes that have been linked to other neurodevelopmental disorders. There is a lot of overlap, noted Arnett, but the mutations are not as extensive in ADHD. In more severe variants, the gene may lose its function and cause intellectual disability, for example, but the changes in the genes are milder in ADHD and only involve one base pair, leading to milder symptoms.
The variations in ADHD symptoms and severity among patients might also be explained by the different genes that can be connected to the disorder, noted the researchers. In additona, this genetic variation could explain why ADHD can be tough to differentiate from other conditions, such as autism.
"Many kids don't fit into diagnostic boxes very well," said Arnett.
This testing won't be available to children and their families yet. With more research that confirms these results, however, it may one day be possible to use genetics to predict who is at risk of developing ADHD, and whether the condition could persist into adulthood.
Sources: Children's Hospital Boston, JAMA Pediatrics
