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Several studies in the past two years have claimed that brain scans can diagnose autism, but this assertion is deeply flawed, says Nicholas Lange.
A study published recently in the widely read clinical journal Radiology correctly identified 36 out of 39 children and adolescents with autism solely by the use of functional magnetic resonance imaging (fMRI)1. The researchers reported that as the subjects listened to their parents' voices, those with autism had lower brain activity in the superior temporal gyrus, a brain region involved in language reception, compared with controls.
Although this finding makes sense, we should be cautious about its interpretation. This is not an autism-detecting brain scan. Language deficits are a core and defining feature of the disorder; one doesn't need a brain scan to show this. And there are many people with language difficulties who do not have autism. Therefore, a technology that detects language problems doesn't move the ball towards a differential diagnosis.
To diagnose autism reliably, we need to better understand what goes awry in people with the disorder. Until its solid biological basis is found, any attempt to use brain imaging to diagnose autism will be futile. I agree with my colleagues who have said that any candidate biomarker for any disorder is of no clinical use unless we first establish a stable and biologically valid concept of the illness2.
During the 70 years since psychiatrist Leo Kanner originally observed and named autism, its diagnostic criteria...