Genetics of Autism
	Twin Studies • Monozygotic twins are about 78% concordant for autism and spectrum disorders. • Dizygotic twins are about 17% concordant. Recurrence Risk • Approximately 3% of affected probands have an affected sibling with autism (15% for autism + spectrum). • Relative risk • Recurrence risk/prevalence • 50-100 fold increase risk to first-degree relatives compared to general population.