A new research has been done to prove that developing a neurodevelopmental disorder like autism or ADHD and the severity of the mental health disease depends on genetic changes that are beyond a single supposedly disease-causing mutation. Led by the researchers from Penn State the research revealed that the total number of rare mutations -- deletions duplications or other changes in the DNA sequence – in the genome can explain why individuals with a disease-associated mutation can have vastly different symptoms. Published in in the journal Genetics in Medicine Santhosh Girirajan associate professor of biochemistry and molecular biology and of