There are highly significant differences when comparing PDA to autism and Asperger syndrome. PDA and its diagnostic criteria are regarded as more complex in comparison.
The following differences are significant at 0.001 level:
PDA children are LESS likely:
PDA children are MORE likely:
The above data is taken from Pathological Demand Avoidance syndrome: Discriminant Functions analysis demonstrating its essential differences from autism and Asperger syndrome: Elizabeth Newson and Kathryn le Marechal, Early Years Diagnostic Centre and University of Nottingham, England.
People with PDA can become obsessive about particular individuals or relationships. They tend to show a high level of impulsivity, excitability and sometimes violent behaviour, often associated with these obsessive interests, and occasionally involving harassment of another child or adult. Their obsessive interests are qualitatively different from those seen in autism/Asperger.
Like all children with a pervasive developmental disorder, people with PDA will have certain communication problems, although these may be masked by their superficially high social skills of distraction and avoidance, thus the underlying deficits can be quite easily overlooked. Semantic pragmatic language (the social use of language, including body language) may also be affected, but not to the degree found in autism and Asperger syndrome. Bizarre content of language is more common than in autism, sometimes due to interest in fantasy.
Individuals with PDA tend to have over-active imagination as opposed to under-active, and this clearly sets them apart from Wing's description of the autistic Triad of Impairments. Individuals with PDA quite often become confused as to the boundaries of reality and imagination (as they also do with other boundaries). They may submerge themselves into characters that they have modelled themselves on, either from TV or from real life, and sometimes they can seem to have lost touch with their 'real' selves. Many children with PDA take on the role of their teacher in great detail, and will tell other children what to do (much to their annoyance!) Keeping the tolerance and sympathy of other children in the classroom can be a difficult task for teachers who are trying to meet the needs of a child with PDA.
Most of the characteristics mentioned tend to persist in various forms into adult life, but research in this area is not extensive at present. The prevalence of PDA compared with autism is not known.