People with autism or ADHD share certain rare mutations, according to researchers from iPSYCH in Denmark, the Broad Institute and Harvard. One of the most commonly shared types of mutations were those affecting the microtubule-associated protein 1A gene (MAP1A), which is involved in the formation of nerve cells. According to this study, the risk of ADHD and autism increases by more than 15 times for people carrying certain MAP1A mutations.
“This is the first time that the genome has been mapped so comprehensively for both ADHD and autism, and the discovery that children with ADHD have the same amount of deleterious gene mutations in their DNA as children with autism is both striking and quite surprising,” says Anders Børglum, who is professor at Aarhus University, principal investigator at iPSYCH and one of the lead authors of the study.
Autism and ADHD can have certain common symptoms, such as violent or aggressive behavior, impulsivity, and having problems in school and with social relations. This study looked at data from 3,962 people in Denmark with autism, 901 with both autism and ADHD, 3,477 with ADHD and 5,002 control subjects without any of the above-mentioned diagnoses. Exome sequencing was carried out on each subject. The researchers also incorporated additional data from approx. 45,000 international control subjects without psychiatric disorders.
The study’s first author is F. Kyle Satterstrom and it appears in the latest issue of Nature Neuroscience.
These new findings point directly towards biological causal mechanisms shared by ADHD and autism.
First, the researchers determined that individuals with ASD and those with ADHD had a similar burden of rare protein-truncating variants in evolutionarily constrained genes, and both had a significantly higher burden of these than controls. Looking more closely, they found:”The gene that is most frequently affected by mutations in people with ADHD or autism is the so-called MAP1A gene. The gene is involved in the formation of the physical structure of nerve cells – their inner ‘skeleton’, so to speak – and is important for the development of the brain,” explains Børglum.
According to the researchers, this is the first time that this gene has been linked to the development of ADHD and autism, and the mutations found give a significantly increased risk of developing autism and/or ADHD. Their work puts the risk of ADHD and autism as more than 15 times higher for people who carry MAP1Amutations.
It is estimated that about 1% of the world’s population suffers from autism, that’s more than 3.5 million people in the US alone. The rate of autism diagnosis in the US has risen by 6-15% every year from 2002 to 2010. ADHD is even more common. It is estimated that 7.2% of children worldwide have this condition.
iPSYCH is one of the world’s largest studies of genetic and environmental causes of mental disorders and now comprises more than 150 researchers within psychiatry, genetics and register-based research. It was founded in 2012 to find the causes of five of the most serious mental disorders; schizophrenia, bipolar disorder (previously manic depression), autism, ADHD and depression. The researchers are examining genes and risk factors in more than 130, 000 Danes who both did and did not suffer from mental disorders.