Aetiology of autism: findings and questions.

BACKGROUND: Although there is good evidence that autism is a multifactorial disorder, an adequate understanding of the genetic and non-genetic causes has yet to be achieved.

METHODS: Empirical research findings and conceptual reviews are reviewed with respect to evidence on possible causal influences.

RESULTS: Much the strongest evidence concerns the importance of susceptibility genes, but such genes have yet to be identified. Specific somatic conditions (such as tuberous sclerosis and the fragile X anomaly) account for a small proportion of cases. Over recent decades there has been a major rise in the rate of diagnosed autism. The main explanation for this rise is to be found in better ascertainment and a broadening of the diagnostic concept. Nevertheless, some degree of true rise cannot be firmly excluded. However, the epidemiological evidence on the main hypothesized environmental explanation, namely the measles-mumps-rubella vaccine, is consistently negative.

CONCLUSION: Progress on the elucidation of the causes of autism will be crucially dependent on the combination of epidemiology with more basic science laboratory studies.