Autism Probably Not Caused by Single Factor
June 7, 2004

NEW YORK (Reuters Health) - In a new study researchers have identified a number of perinatal factors that are associated with an increased risk of autism. Several obstetric complications were linked to the disorder, which the authors believe are most likely also the result of underlying genetic factors.

"To our knowledge, this study is the largest reported population-based sample to date of people born and diagnosed with an autism spectrum disorder within a single geographical area, using prospectively collected obstetric data and comparing siblings and autism subgroups in a single research design," lead author Dr. Emma J. Glasson, from the University of Western Australia in Crawley, and colleagues note.

The study involved 465 patients born in Western Australia between 1980 and 1995 and diagnosed with autism spectrum disorder by 1999. Comparison groups included 481 siblings of the case patients and 1313 population-based controls.

The researchers' findings are published in the June issue of the Archives of General Psychiatry.

Compared with controls, case patients were more likely to be first born and to have older parents, the authors note. In addition, an increased frequency of threatened abortion, epidural caudal anesthesia use, labor induction, and labor lasting < 1 hour was seen among mothers of case patients.

Obstetric complications linked to autism spectrum disorder included fetal distress, delivery by c-section, and a 1-minute Apgar score of < 6. Among patients with the disorder, those with autism experienced more complications than patients with pervasive developmental disorder NOS or Asperger syndrome. The complication profile of nonaffected siblings was more similar to that of their affected sibling than to that of control subjects.

"It is unlikely that single factors or events cause autistic disorders, although it is possible that early nongenetic influences may act on the causal pathway for some cases," the investigators state. The current findings support the hypothesis that the development of such disorders primarily depends on the genotype, they add.

Arch Gen Psychiatry 2004;61:618-627.