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.

One of the largest genome-wide association studies for autism spectrum disorders, reported last week in Human Molecular Genetics, allows only one definitive conclusion: it isn’t large enough.

Several independent groups have found previously unknown risk genes for autism, schizophrenia and mental retardation. The candidate genes have one thing in common: they encode proteins that are needed for the healthy function of synapses, the junctions between neurons.

A whopping 95 percent of children with autism have at least three other psychiatric disorders, and 74 percent have five or more, according to a study in the Journal of Autism and Developmental Disorders.

Several studies in the past year in people, mice and honeybees have tied autism to a protein that helps neurons communicate. Problems with the protein, neurexin 1, are associated with a wide range of autistic behaviors, such as impaired social interactions, anxiety and problems with learning and memory.

Writing in Science, leading scientists call for a 10-year, $2 billion international scheme that would combine the latest in genetics and animal research to combat psychiatric diseases.

We know that carrying one specific DNA variant can increase your risk of autism. What if you carry two?

The proposed connection between premature birth and autism may be more complicated than it seems, according to a new report. Early birth may not cause classically defined autism but, rather, may predispose children to autism-like symptoms that are part of a larger syndrome, the researchers say.

Several genetic and animal studies in the past year have found intriguing ties between autism and DISC1, one of the oldest candidate genes for psychiatric disorders.

Researchers are using dogs as models of psychiatric and behavioral conditions, including obsessive-compulsive disorder and autism.