A new study published in Thursday's New England Journal of Medicine adds to the theory that autism may start in the womb.
Autism researchers at the University of California, San Diego, examined the brains of children with autism who died.
They found abnormal patterns of cell growth in tissue samples from regions important for regulating social functioning, emotions and communication — which can all be troublesome for children with autism, the Associated Press reports.
The abnormalities were found in 10 of 11 children with autism, but in only one of 11 children without the disease. The children's brains were donated to science after death; causes of death included drowning, accidents, asthma and heart problems.
The authors of the study said the clusters, detected with sophisticated lab tests, are likely defects that occurred during the second or third trimesters of pregnancy.
There is often nothing about how people with ASD look that sets them apart from other people, but people with ASD may communicate, interact, behave, and learn in ways that are different from most other people. The learning, thinking, and problem-solving abilities of people with ASD can range from gifted to severely challenged.
A diagnosis of ASD now includes several conditions that used to be diagnosed separately: autistic disorder, pervasive developmental disorder not otherwise specified (PDD-NOS), and Asperger syndrome. These conditions are now all called autism spectrum disorder.
Autism is more than twice as common as officials said it was just seven years ago.
The Centers for Disease Control and Prevention estimates autism affects roughly 1.2 million U.S. children and teens. The estimate means 1 in 68 U.S children have autism or a disorder related to autism, The Washington Post reports.
The paper notes that health officials say the new number may not mean autism is occurring more often. Much of the increase is believed to be from a cultural and medical shift, with doctors diagnosing autism more frequently, especially in children with milder problems.
There are no blood or biologic tests for autism, so diagnosis is not an exact science. It’s identified by making judgments about a child’s behavior.