Three articles published in the past few weeks show that diagnostic categories marked off neatly on the page often bleed together messily in the clinic.

The Autism Birth Cohort, based on data from 100,000 Norwegian children and their families, aims to uncover genetic and environmental factors contributing to the disorder.

A region of the brain that controls language is more extensively curved in children with autism than in those with Asperger syndrome, according to a study published in the Journal of Child Neurology. The findings offer preliminary biological evidence that Asperger syndrome, a disorder on the autism spectrum, is distinct from high-functioning autism.

Attention deficit hyperactivity disorder (ADHD) and autism may have more in common than childhood onset and a few similar symptoms. New research suggests the conditions share genetic roots.

The psychiatrists who literally write the book on the definitions of mental illness have announced their plan to group all autism spectrum disorders, including Asperger syndrome, under a single category.

A newer version of the psychiatric manual may expand the definition of autism, folding in Asperger syndrome and pervasive developmental disorder not otherwise specified.