Today, children in the UK are nearly three times less likely than those in the US to be labelled with the conditions. Around four in 1,000 children in the UK are diagnosed with autism, compared to 11 per 1,000 in the US. The same levels of diagnosis are also seen in cases of ADHD.
The stark contrast between the two nations started to appear at the start of the decade, when diagnoses of new cases dropped dramatically in the UK from the year 2000 onwards. Up to then, the UK was keeping pace with the US, and the rate of new cases had increased five-fold throughout the 1990s. The US has continued to see an increase, however, with a 78 per cent rise in the rate of new cases diagnosed in children aged eight between 2004 and 2008.
Researchers aren't sure why UK rates rose so dramatically in the 1990s, and have flat-lined since, other than to suggest the whole thing is a mystery. Perhaps it's all to do more with fashion than genuine diagnosis.
(Source: British Medical Journal, 2013; 3: e003219)