Ricardo Espinoza L/ShutterstockWhen Donald Trump gave a press conference in late September urging pregnant women to avoid taking paracetamol unless medically necessary because of a possible link to autism, the reaction from the scientific community was swift and loud. There is no scientific evidence that paracetamol – commonly sold as Tylenol in the US – causes autism. Instead, decades of research points to a complex interplay of genetic and environmental factors that may increase the risk for autism, although no one gene for autism has been identified. Trump’s finger-pointing at paracetamol was part of a push by his health secretary, Robert F Kennedy Jr to explain a sharp rise in the number of autism cases in recent decades that he’s labelled an “epidemic”. Yet, as American politicians give oxygen to unproven theories about what might be behind the rise, experts repeatedly point to the changing nature of how autism is diagnosed and viewed. A key moment in the history of autism diagnosis was the publication in 1994 of a new version of the Diagnostic and Statistical Manual of Mental Disorders IV (DSM). The DSM, published by the American Psychiatric Association, is a reference book of psychiatric conditions and how to diagnose them. It’s based on the latest science and is used by psychiatrists and psychologists around the world.In this episode of The Conversation Weekly podcast, we speak to Andrew Whitehouse, a professor of autism research at the University of Western Australia, about why this shift in autism diagnosis happened in the 1990s, what impact it had, and what it’s meant for the support autistic people get. When I started in the field in 1998-9, we diagnosed about one in every 2,000 children. That was pretty much the same in every anglo-western country … Nowadays, in Australia we’re seeing diagnosis of one in every 40 children. That’s an extraordinary increase.Listen to the conversation with Andrew Whitehouse on The Conversation Weekly podcast. This episode of The Conversation Weekly was written and produced by Katie Flood, Mend Mariwany and Gemma Ware. Mixing and sound design by Michelle Macklem and theme music by Neeta Sarl.Newsclips in this episode from NBC News, NBC Montana and Rain Man.Listen to The Conversation Weekly via any of the apps listed above, download it directly via our RSS feed or find out how else to listen here. A transcript of this episode is available on Apple Podcasts or Spotify.Andrew is a Director on the Board of Autism Awareness Australia.