In families with more than one child diagnosed with autism, younger siblings appear to be more severely affected by the disorder, according to new data presented Tuesday at the Society for Neuroscience annual meeting in San Diego.

Scientists have pinpointed two major gene networks relevant to autism by analyzing gene expression in brain tissue from individuals with the disorder. Researchers presented the data Sunday at the Society for Neuroscience annual meeting in San Diego.

Infection early in pregnancy is more harmful to the fetus than at later stages, triggering brain and behavioral changes in the offspring similar to those seen in people with schizophrenia, according to two mouse studies published in October. A third study suggests that exercise can mitigate some of these effects.

People with autism may belong to one of four distinct categories based on their medical history, according to a study published in the October Autism Research.

Two new studies use medical records from countries with nationalized health care to link autoimmune disease and obesity in parents to the likelihood of having a child with autism.

Chemicals produced by their mother’s immune system in utero alter the size of several key brain regions in people with schizophrenia, enlarging chambers that store cerebrospinal fluids, and shrinking parts of the cortex involved in processing emotion and memory.

A study of postmortem tissue shows that microglia, cells that provide immune protection to the brain, are altered in the brains of individuals with autism.

In order to understand the interaction between genes and environment in autism, researchers in different disciplines will have to move back and forth between those two realms, stretching out of their intellectual comfort zones. But if the mood at an interdisciplinary workshop two weeks ago is any indication, that challenge is also a source of excitement.

The biology of obsessive-compulsive disorder becomes even more baffling with the release of two new mouse models, each implicating a different type of brain cell.

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.