Are autism spectrum disorders (ASD) really more prevalent or are we just better at collecting the data and identifying the disorder at younger ages?

"It's likely both," says Judith Miller, PhD, training director at the Center for Autism Research, Children's Hospital of Philadelphia. Also contributing to the increased number of diagnoses is heightened awareness of subtle forms of ASD and broader application of the diagnostic criteria, she adds. Then factor in new data suggesting that 15 percent to 30 percent of autism cases may be due to the increasing average age of new fathers (see Catching autism earlier).

When it is released next year, the Diagnostic and Statistical Manual of Mental Disorders-5 is expected to combine the subgroups of Asperger's syndrome, pervasive developmental delay (PDD) and autistic disorder into one broad category—autism spectrum disorder, or ASD. While some wondered if combining the criteria for these subgroups in DSM-5 would lead to fewer people being diagnosed with autism, a study this year in the Archives of General Psychiatry (Lord) suggested it will have little effect in that regard.

Further, the data collected from 12 university-based sites suggests that removing these subtypes will make it easier to make accurate, consistent ASD diagnoses, says study co-author Ellen Hanson, PhD, a psychologist and research lab director at Boston Children's Hospital.

On a practical level, having one overarching diagnosis in DSM-5 may help some people with ASD access additional treatment and support, Hanson notes. People with diagnoses such as Asperger's have not always been eligible for certain services.

—Eve Glicksman