A naturally occurring hormone that’s been prescribed to many children with autism under the thinking that it could boost sociability does not in fact make any difference, according to a large new government-funded study.

There have long been high hopes that using a nasal spray of oxytocin, a hormone often used to induce labor, could treat socialization difficulties associated with autism. The theory gained traction over the last decade or so with some small studies showing promising results.

But now researchers behind the largest study of its kind on the issue say that while the hormone is safe, it does not provide benefits.

“There was a great deal of hope this drug would be effective,” said Dr. Linmarie Sikich, an associate consulting professor in the Department of Psychiatry & Behavioral Sciences at the Duke University School of Medicine and the study’s principal investigator and lead author. “All of us on the study team were hugely disappointed, but oxytocin does not appear to change social function of people with autism.”

The research published this week in The New England Journal of Medicine involved 290 children with autism ages 3 to 17 who either received oxytocin or a placebo daily for 24 weeks. The children’s social abilities were assessed before starting the treatment, halfway through and again at the end of the study period.

Overall, the researchers found that oxytocin was well tolerated and there were few side effects, but there were no significant differences between the kids who received the hormone and those who did not.

“Thousands of children with autism spectrum disorder were prescribed intranasal oxytocin before it was adequately tested,” said Dr. Jeremy Veenstra-VanderWeele of New York State Psychiatric Institute and Columbia University, a senior author of the study. “Thankfully, our data show that it is safe. Unfortunately, it is no better than placebo when used daily for months.”

Veenstra-VanderWeele said the findings show that clinicians and families should expect “strong evidence for the safety and benefit of new treatments” before they are put into use.