Autism is largely genetic, but evidence also points to "triggers" in the prenatal environment.
Worry has always been a side effect of pregnancy. But one anxiety--will my baby be normal?--has recently come to include a new concern: autism. First identified in 1943, the disorder is commanding unprecedented interest, mostly because of the reported rise in its incidence, but also because its origins lie in the fascinating crux between genes and the environment. "Autism is primarily genetic, but something beyond genes is also involved," says pediatric neurologist Andrew Zimmerman, M.D., an associate professor of neurology at Johns Hopkins University School of Medicine and a research scientist at the Kennedy Krieger Institute in Baltimore. That something may be found in the womb.
Among the most intriguing areas of investigation is how environmental influences might "hijack" fetal genes and alter their effect on brain development. But tracking cause and effect in such a complex syndrome is difficult, and scientists expect that results will come slowly. "If you think of autism research as a game of Monopoly, we just passed Go," says toxicologist Isaac Pessah, Ph.D., director of the Children's Center for Environmental Health and Disease Prevention at the University of California, Davis.
The who, what and when of autism
Neither a disease nor a mental illness, autism is a behavioral syndrome that originates early in life, possibly well before birth. It's the most severe of a range of developmental problems known as autism spectrum disorders (ASD), and it affects far more boys than girls. Whether its incidence is increasing remains controversial (see "Autism's Rise: Real or an Illusion?" at left), but everyone agrees that the syndrome has a powerful impact on affected children and their families.
Because their brains are "wired" differently, autistic children may react intensely to sensations such as sound and touch. Most have limited interests and trouble with language, social skills, communication and attention. Only recently have scientists understood that autism is actually several different disorders, the causes of which may involve many different genes and environmental exposures.