More than 100 genes associated with autism were identified in a "landmark study" that could help better understand what causes the disability, researchers say.

In the large genetic-sequencing study, a team of researchers led by scientists at Mount Sinai and relying on international collaboration identified the 102 genes associated with autism spectrum disorder (ASD).

The team relied on samples from more than 35,000 participants, of which almost 12,000 had autism, and they were able to study both genes that were inherited and those that occurred when egg or sperm are formed.

Of the 102 genes, 49 were also tied with other development delays, the researchers say.

"With these identified genes we can begin to understand what brain changes underlie ASD and begin to consider novel treatment approaches," Joseph Buxbaum, the director of the Seaver Autism Center for Research and Treatment at Mount Sinai, said in a statement.

The study was published Thursday in the peer-reviewed journal Cell.

In 2015, only 65 genes associated with ASD were known, the researchers say. Dr. Andrew Adesman, the chief of developmental and behavioral pediatrics at Cohen Children’s Medical Center of New York, said the study is the latest in a string of advances to help understand the genetic factors associated with autism in some children.

"Identification of these new genes associated with autism may not only help pinpoint a likely cause for ASD in some children, but it will also help researchers better determine the biological mechanisms that underlie autism," he wrote in an email to USA TODAY. Adesman was not involved in the study.

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Autism spectrum disorder affects communication and behavior, and its effects usually appear early in life, according to the National Institute of Mental Health.

The condition is known as a spectrum disorder because an array of behaviors and their severity may vary depending on the individual, the institute says.

Reduced eye contact, lack of response to their name or indifference to caregivers are among some of the traits seen in early infancy, according to the Mayo Clinic. Some children later become withdrawn or aggressive or lose language skills, the hospital says.

About 1 in 59 children has been identified with ASD, according to data from the Centers for Disease Control and Prevention.

Adesman said the research is encouraging because with genetic testing, the findings increase the likelihood of determining a probable genetic cause for some children's autism. Still, Adesman tempered some exceptions: "Unfortunately, even though this latest research has newly identified many genes associated with ASD, the reality is that for many affected children, a specific cause may not be identified."

Among the other findings in the study: No one major class of cells alone are tied to autism, instead, a host of disruptions in brain development and in neuronal function can lead to the condition, Buxbaum said.

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