https://www.autismsocietycanada.ca/understanding_autism/what_are_asds/index_e.html
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Each individual is unique - no one person with an ASD responds or behaves exactly like another with the same diagnosis.
There are Five Pervasive Developmental Disorders (PDDs)
Childhood Disintegrative Disorder (CDD)
Rett's Disorder (RD)
Autistic Disorder (AD)
Pervasive Developmental Disorder - Not Otherwise Specified (PDD-NOS)
Asperger's Syndrome (AS)
Childhood Disintegrative Disorder (CDD)
Rare: ~0.2 in 10,000 Canadians
Significant losses in social behaviour, language, play and adaptive behaviour after period of normal development of 3 or more years
Severe deficits in cognitive ability
Rett Syndrome (RTT)
Rare: ~1 in 10,000 female births
A developmental disorder found almost exclusively in girls
Symptoms appear after an early period of apparently normal or near normal development until six to eighteen months of life, when there is a slowing down or stagnation of skills
Often misdiagnosed as autism or cerebral palsy
RTT causes problems in cognitive, sensory, emotional, motor and autonomic function. Can affect learning, speech and communication, sensory sensations, mood, movement, breathing, cardiac function and psycho-motor skills
Disabilities caused by Rett Syndrome range from mild to severe.
Autistic Disorder (AD)
Most common: ~20 in 10,000 Canadians
Cognitive impairments
Deficits in verbal and non-verbal communication
Deficits in social understanding
Unusual behaviours, restricted activities
Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS)
Common: ~15 in 10,000 Canadians
Also called atypical autism
Severe and pervasive impairment in some areas such as reciprocal social interaction, or restricted activities and interests but the strict criteria for autistic disorder are not met
Asperger Disorder (also called Asperger's Syndrome, Asperger Syndrome, and AS)
Common: ~5 in 10,000 Canadians
Mild to severe impairments in social interaction and understanding
Restricted and repetitive activities and interests
Language and cognitive development not delayed
Deficits in communication
Reference for prevalence:
Fombonne, E., 2003: Modern Views of Autism, Can. J. Psychiatry, 48:503-505.
Fombonne, E., 2003: Epidemiology of autism and other pervasive developmental disorders: an update. J. Autism.Dev. Disord. 33:365-381
Related Conditions
Several other medical conditions also include some features of PDD, such as Down Syndrome, Prader-Willi Syndrome, Fragile X Syndrome, Landau-Kleffner Syndrome, William's Syndrome or Tourette's Syndrome but PDD does not actually include these medical conditions.