Helping parents understand and respond to their infant's early communication efforts through video feedback-based therapy might aid in modifying or ameliorating emerging autism symptoms, a study has found.

Families with babies at risk of autism can use the video therapy to improve infants' engagement and social behavior, says study leader Jonathan Green, a professor of child and adolescent psychology at Manchester University in England.

"Targeting the earliest risk markers of autism, such as lack of attention or reduced social interest or engagement, during the first year of life may lessen the development of these symptoms later," he says.

The study was conducted with 54 families whose babies were considered at increased risk of autism because an older sibling in the family had the condition.

Previous research has suggested around 20 percent of infants with an older sibling with an autism spectrum disorder develop the condition themselves.

Some of the study families were assigned to a therapy program involving "video feedback" where parents watched videos of their interactions with their baby along with a therapist who made home-based visits to aid parents in learning how to respond to their infants' communication styles.

Other families became a study control group that did not receive the video therapy.

After 5 months, babies in the families assigned to the video therapy group -- ages 7 to 10 months at the start of the study -- showed improvements in their attention span, engagement level and appropriate social behavior, the researchers reported in The Lancet Psychiatry journal.

The findings suggest that although early intervention cannot prevent autism, features of the disorder may be lessened in high-risk children through the use of strategies such as the video-feedback therapy, the researchers say.

"We preach this idea that intervention changes something in the brain, but we rarely have proof of that," says study researcher Mayada Elsabbagh, an assistant professor of psychiatry at McGill University in Montreal. "This is one of the first times in my career that I've seen that so clearly."

While the babies in the study are too young to be assessed for possible autism -- such a diagnoses normally happens around 2 to 3 years of age -- the findings offer strong evidence that intervention may help reduce later symptoms.

However, larger studies would be needed to replicate and confirm the possible benefits of the video-feedback therapy, Green says.

"We would never want to say that early intervention is the only thing that's needed in autism," he says. "But there's something about early development that might be amenable to intervention."