New cases of autism in children have levelled off in the UK after a 1990s surge, researchers said.
The occurrence of autism in eight-year-olds reached a plateau in the early 2000s and remained steady throughout 2010, they found.
Writing in the online journal BMJ Open, experts said the cause of the surge in the 1990s “remains in large part a mystery”.
One explanation is that changes to the way autism was diagnosed captured more cases, but this is unlikely to explain the five-fold increase seen.
In the new study, experts from the University College London Institute of Child Health and elsewhere analysed data from the General Practice Research Database, which contains around three million anonymous patient records from GP surgeries in the UK. The typical prevalence of autistic spectrum disorders each year was estimated at 3.8 per 1,000 boys and 0.8 per 1,000 girls. The annual number of new cases was 1.2 per 1,000 boys (1,190 in total), 0.2 per 1,000 girls (217 in total).
The authors said: “In conclusion, the annual prevalence of clinically confirmed autism recorded by UK GPs remained steady for the seven-year period 2004 to 2010.”
Carol Povey, director of the centre for autism at the National Autistic Society (NAS), said: “This study shows that, contrary to media hype, autism has been with us for a long time.
“Evidence suggests that the increase in diagnoses of autism is in large part down to greater awareness of the condition, as well as better diagnostic facilities and improved skills and knowledge among those who carry out diagnoses. More than one in 100 people in the UK have autism and it’s important that we work to ensure they receive the support they need to reach their full potential.”
The study comes as separate research found children with autism were seen as less friendly and trustworthy by their peers, based solely on appearance.
The research, published in the journal Autism, found youngsters were less positive towards children with autism and formed negative impressions after a 30-second encounter.
Dr Steven Stagg, senior lecturer in psychology at Anglia Ruskin University, and psychologists at Royal Holloway, University of London, investigated the initial impressions “typically developing children” form when watching silent videos of children with autism and comparing them with other children. The children were unaware they were watching videos of youngsters with autism.
Typically developing children believed youngsters with autism were less trustworthy than other youngsters. They were also less likely to want to play with them or be their friend.
Dr Stagg said: “Children with autism have a difficult time at school, and research published by the National Autistic Society showed that 40 per cent of children with autism reported being bullied.”
He added: “It is important schools work with typically developing children to educate them about autism in order to break through the negative impressions that can be formed through a moment’s contact.”