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.

Babies born to rhesus monkeys infected with the flu virus during pregnancy have significantly smaller brains than normal, and other brain abnormalities seen in schizophrenia, researchers have found. The study, published last month in Biological Psychiatry, provides the first evidence in non-human primates linking flu infection to a higher risk of schizophrenia.

Mice engineered to carry a well-known risk factor for schizophrenia show disruptions in the connections between two brain regions that coordinate memory and learning. And these disruptions directly cause problems with working memory — the ability to actively hold information and to recall that information to make a decision, according to a study published in Nature.

People with autism harbor more copy number variants (CNVs) — deletions or duplications of large chunks of DNA — compared with controls, but only in the protein-coding regions of the genome, researchers reported Wednesday in Nature. The study also pinpointed more than 100 new risk genes for autism.

Some brain areas involved in speech are larger and some smaller in children with autism compared with healthy controls, according to a series of imaging studies conducted by a Boston research group.

Two independent teams have identified the genetic culprits of three rare, inherited diseases by sequencing the genomes of several members of the same family. As the cost of whole-genome sequencing plummets, this family-based approach will reveal candidate genes not just for rare diseases but for common, complex disorders such as autism, experts say.

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.

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.

Researchers have found a higher density of several types of interneurons — nerve cells that connect sensory and motor neurons in the brain— in postmortem brain tissue from individuals with autism, compared with healthy controls. The findings appear in the February issue of Acta Neurologica Scandinavica.

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.