The high levels of serotonin seen in the blood of some autistic people have confounded scientists for more than half a century. Despite so little progress, some researchers refuse to give up.

Worms and zebrafish missing both copies of the gene CHD7 have disrupted cellular signaling, a dearth of inhibitory neurons and behavior changes — all of which are reversed by the stimulant drug ephedrine.

Elizabeth Berry-Kravis has spent decades uncovering molecular clues to fragile X syndrome and crafting trials of treatments. Her efforts are paying off.

Researchers have defined a change in score on a popular autism rating scale that signifies a meaningful improvement in core traits. The measure could help scientists assess the effectiveness of autism treatments in clinical trials.

Multiple types of bias and an overreliance on caregiver reports have clouded research on the effectiveness of early interventions for autism for nearly three decades.

The investigational drug arbaclofen may right an imbalance between inhibitory and excitatory signaling in the animals’ brains.

A drug that prevents an enzyme from breaking down a key molecule involved in learning and memory improved cognition and behavior in a small study of men with fragile X syndrome.

Applied behavior analysis is the most widely used therapy for autistic children in the United States, but some regions lack the staff needed to provide it.

Motor and memory training early in life postpones the onset of difficulties in those areas in a mouse model of Rett syndrome, and stimulating neurons involved in those skills appears to mimic the effects of training.

To guard against hype, scientists studying oxytocin’s role in autism and its potential as a treatment need to embrace robust theories, rigorous delivery methods and reproducible research practices.