Every day our brains help us make sense of the world around us, interpreting the experiences we see, hear, taste, touch and smell. But if someone’s brain has trouble processing this incoming information, it can be hard to communicate, understand or learn.
Autism spectrum disorders (ASD) are characterized by difficulties in social interaction, verbal and nonverbal communication and repetitive behaviors. These disorders include autism, Asperger syndrome and pervasive developmental disorder-not otherwise specified (PDD-NOS).
About one in 88 children have been identified with an autism spectrum disorder, and over 2 million people are affected in the United States, according to the Centers for Disease Control and Prevention. Government statistics also suggest that the proportion of people with autism spectrum disorders have increased 10 to 17 percent annually in recent years. This is in part due to wider awareness and better screening, but the continued increase is not fully understood.
The cause of ASD is also not fully known, but current research indicates that it is likely due to a complex combination of genetic predisposition and environmental risk factors that influence early brain development. Significant environmental risk factors include the advance age of either parent at the time of conception, maternal illness during pregnancy, extreme prematurity and very low birth weight.
Over 40 years ago, epidemiological studies determined that the risk of having a child with ASD is increased when the mother has an infection early in the pregnancy. Since a wide range of bacterial and viral infections can increase the risk, studies suggest that activation of the mother’s general immune system is responsible. However, scientists do not completely understand how the activated immune system can disrupt normal brain development to cause ASD.