The epidemiology of autism in Western Australia

[Truncated] Autism is a neurodevelopmental disorder that is characterised by impairment in social interaction and communication and by a presence of stereotypic behaviour. It is considered to be a genetic disorder that may have environmental influences in some cases. People diagnosed with autism show large individual differences in their symptomatology and although unusual features are often noticed by 12 months of age the diagnosis is not typically made before 3 years of age. There are many aspects of autism and the related autism spectrum disorders, Asperger syndrome and Pervasive Developmental Disorder Not Otherwise Specified, which remain unknown. The aetiology, the relevance of various physical characteristics, the importance of prenatal associations, and the association with biological markers in people who develop the disorders are yet to be identified. It is important to examine these issues within large populations using high-quality data. The presence of obstetric complications was investigated amongst all known people diagnosed with an autism spectrum disorder born in Western Australia between 1980 and 1995 (n = 465). Birth records were extracted from the state Maternal and Child Health Research Database, which is a register of information collected at the time of birth. The case siblings (n = 481), a random sample of non-autism births matched for sex (n = 1313), and their respective siblings (n = 1634) were used as control groups.