No one disputes that diagnosed rates of autism have increased enormously over the past 15 years or so, around the world. However, other people write it off as essentially a cultural phenomenon: we’re getting better at detecting the disorder and more willing to label kids as having it.
I subscribe to the latter view, but there’s very little hard evidence for it. To prove that diagnostic changes have occurred, rather than a true increase in autism, you’d have to know what would have happened to today’s kids, say, 20 years ago. Would they have been diagnosed? We have no way of knowing. At least not until someone invents a time machine.
However, a new study just out offers a valuable new perspective on the debate: Spatial clusters of autism births and diagnoses point to contextual drivers of increased prevalence.
According to authors Soumya Mazumdar and colleagues, there’s a zone of high autism prevalence in California, areas where kids aged 0-4 years old are more likely to be diagnosed with the condition. The epicentre is L.A.; there’s actually three overlapping hotspots centred on Santa Monica, Alhambra and North Hollywood.
In these clusters, autism rates are between 2 and 6 times higher than the rest of the state.