The U.S. has recorded a three-fold increase in autism diagnoses, and recent research suggests that something other than vaccines may be responsible for the surge. According to a report from UPI, the increase is mainly due to the reclassification of people with other disorders, and not necessarily a rise in the number of people who actually suffer from autism.

Scientists have attributed the mass reclassification in part to the similarities between autism and other neurobiological disorders. There has also been a loosening of the criteria for autism diagnostics.

According to data from the Center for Disease Control and Prevention, autism rates have increased from 1 in 5,000 in 1975, to 1 in 150 in 2002, all the way to 1 in 68 in 2012.

Based on observational evidence, scientists found it hard to accurately diagnose autism cases because patients often exhibited many different combinations of characteristics of a wide range of other disorders. According to Santhosh Girirajan, an assistant professor of biochemistry and molecular biology and anthropology at Penn State University, the criteria for diagnoses have been widened to address the variations in autism cases.

The study followed an average of 6.2 million children in special education classes between 2000 and 2010 using information from the Individuals with Disabilities Education Act (IDEA). They found a 331 percent increase of autism cases over the course of the last decade.

About 65 percent of this uptick can be ascribed to the reclassification of children from intellectual disability to autism. About 59 percent of 9-year-olds were reclassified as autism patients, and that figure jumped to 97 by the time many of the children reached age 15.

The wide range of mental characteristics of autism makes it difficult to diagnose, but a 300+ percent increase in reported cases may not be the best way to learn more about the disorder.