AbDn is a very serious form of A.D.D.N. and Autism. It may cause deformity, death, sensitivity to sound, and etc. People with AbDn behave like toddlers and have obsessions with objects. Also, people can or cannot talk and some might die at birth or at a young age.
The first known person with AbDn is George Pig.
There was a conspiracy theory about Elsa Elephant having AbDn in 2010, but it was proven wrong.