After years of rising cases of autism, the number of kids diagnosed with the developmental disorder might be leveling off, according to new statistics.

Survey data suggest cases of autism among children and adolescents have not jumped over the last few years in the same way they did for the 20 years before, according to a research letter in the Journal of the American Medical Association. The rate of kids diagnosed with autism, which comes with symptoms that interfere with communication abilities and social skills, has become more stable.

“Previous surveys have reported a steady increase in ASD prevalence in U.S. children over the past two decades,” the letter says. But in recent years, the numbers have hit a “plateau” — between 2014 and 2016, the estimate of children and adolescents with autism was about 2.4 percent, “with no statistically significant increase over the three years.”

The letter explained, however, that the estimated prevalence of the developmental disorder was based on self-reported diagnoses. Family respondents during the survey were asked if a doctor or other health professional had diagnosed a child with an autism spectrum disorder, which includes Asperger’s syndrome and autistic disorder.

The survey information was gathered through the Autism and Developmental Disabilities Monitoring Network, which is funded by the U.S. Centers for Disease Control and Prevention.

As the researchers note, the survey results follow previous findings of a possible plateau in diagnoses in 2012.

A leveling of autism diagnoses does not translate to fewer kids developing the disorders — the data only speak to the number of reported cases.

“This is a descriptive study, so the researchers did not gather information about underlying causes for the findings and cannot make conclusions about their medical significance,” JAMA reported.

Scientists have been getting closer to the root of autism, finding differences in brain structure and neural connections among kids with the disorders. They have also found possible connections between autism and hormone and vitamin levels. One study found that children on the autism spectrum were born with less vitamin D in their bodies, while another found that symptoms of autism dissipated in rats who were treated with the hormone oxytocin.

This article originally appeared in Medical Daily.