(Nature) – RFK Jr has vowed to find out what’s responsible, but scientists say he is ignoring answers from decades of research.

There are several reasons to think that a rise in diagnoses explains a large part of this trend. One is that the diagnostic criteria have changed over time in two periodically updated tools used by health professionals: The Diagnostic and Statistical Manual of Mental Disorders (DSM), used mainly in the United States, and the International Classification of Diseases (ICD).

These describe autistic people generally as showing differences in social interaction and communication, as well as having ‘restricted and repetitive behaviours and interests’. But until the early 1990s, the manuals had a narrow definition for autism, says Diana Schendel, an epidemiologist who studies autism at Drexel University in Philadelphia, Pennsylvania. For instance, the third edition of the DSM recognized autism only in young children and required that they meet a minimum number of criteria. (Read More)