New research in genetics from the Université de Montréal shows that a gene mutation linked to autism spectrum disorder (ASD) can regularly result in a 25 point drop in IQ.
What’s more, those carrying the mutation may or may not manifest outward symptoms of autism.
The study looked at 700 family members who had at least one relative carrying the 16p11.2 gene deletion on chromosome 16, thought to predispose to ASD, and found that the people carrying the mutation, even those who showed no signs of either mental health issues or abnormal cognitive abilities, were regularly testing at a 25 point drop in IQ. A further result showed that the addition of a gene copy in the same genomic region also resulted in a 16 point decrease in IQ.
“Intellectual faculties are the sum of many factors,” says Dr. Sébastien Jacquemont, geneticist and clinical researcher at CHU Sainte-Justine and professor at the Université de Montréal, “the majority of which are genetic and inherited from parents. Strangely enough, even if carriers show much differentiated sets of symptoms – and sometimes no symptoms at all – the specific effect of these two mutations seems to remain the same.”
The University of Montreal study concludes that further work is needed to quantify and characterize the effects of genetic mutations associated with autism. The study was published online in the journal JAMA Psychiatry.
In Canada, the rates of autism spectrum disorder are on the rise. Though there have been no recent nation-wide data on ASD, according to the National Epidemiologic Database for the Study of Autism in Canada (NEDSAC) the prevalence of ASD is estimated at one case per 94 children.
In the United States, the Center for Disease Control (CDC) estimates that one in 68 children is identified with ASD.
Diagnosing ASD is difficult, as doctors and specialists have to rely on behavioural and developmental assessments to locate disorders. According to the CDC, autism disorders can sometimes be detected at 18 months or younger and by age 2 many diagnoses are considered reliable, but in many other cases a definitive diagnosis is not possible until years later.
Last year, CTV News reported that a genetic indicator for autism may become a reality. Researchers at Toronto’s Hospital for Sick Children conducted a study with more than 250 children with suspected ASD diagnoses and found that when two separate genetic tests were combined – a chromosomal microarray analysis (CMA) and whole-exome sequencing (WES) -16 per cent of the children were found to have an ASD-related genetic indicator.
Shane Cunningham Boles, a development co-ordinator with Autism Ontario, says “Many children don’t get diagnosed for many years, so with the genetic testing and the increased diagnosis, it will lead to better support for those kids affected by autism,” According to Autism Ontario, Canadian support systems and services for children and, especially, for adults affected with ASD are inadequate to suit the current needs of families dealing with ASD.