Is autism genetic?

Autism is a behaviorally defined pervasive developmental disorder that affects how a child functions in several areas, including speech, social skills and behavior. Children who have problems in these areas are sometimes said to have an autistic spectrum disorder (ASD) because the severity of symptoms varies greatly.

Autism affects about 1 in 44 children in the United States. More children than ever are being diagnosed with autism. The rates of diagnosis of ASD are about 10 times higher than in the 1980s, though much or all of this increase may be due to improved awareness and changes in how autism is diagnosed.

Genetically, it is clear that the ASD represents a number of different disorders which have some overlap in features. Genetic inheritance has been strongly suggested by studies of twins and families with multiple affected children. Overall, it is believed that there are many genes involved in ASD along with possible environmental or immunologic triggers.

A number of studies have been performed to estimate the recurrence risk in families who already have a child with ASD. The recurrence when there is a child in the family with autism spectrum disorder could be much higher depending on the number of affected siblings and their gender. For mothers, regardless of the sperm source, the recurrence risk to have a second child with autism is as high as 18.7%. If a man has a child with autism, and then goes on to have a child with a different egg source, the risks are slightly higher than 1/44. The difference between the role of the mother and father are not known at this time, but environmental exposure during the pregnancy is being studied. At the current time, there are no prenatal tests to detect children who will be affected with ASD.