The review said not every difficulty required a medical response and there was a risk of blurring the lines between diagnosable ADHD and autism and what should be considered the normal human variation in brain function, cognition and behaviour.
It said there was a risk society was now moving from an era of under-diagnosis to over-diagnosis or mis-diagnosis, pointing to data showing more than 4% of children aged six to 17 were now diagnosed with autism, well above the 1-2% that studies suggest is the true level.
But it said because some of these figures date back nearly a decade it was not possible to be absolutely certain or conclude over-diagnosis was currently occurring at scale.
Mel Merritt, of the National Autistic Society, said the report shows that successive governments “have failed autistic people”.
“The harm and distress autistic people are facing is real and widespread and there is a desperate need to build a system that supports the needs of autistic people.”
Abigail Ampofo, of charity YoungMinds, said: “For years, young people have told us they feel blamed for their mental health or accused of making it up. We hope this review goes some way to show them their distress is not their fault and the systems around them are failing.”
But she said that would require major reform.
The government welcomed the publication of the report and said it would be setting out a new model of providing support in its forthcoming mental health strategy, which is expected before the end of the year, and also promised to introduce tougher regulation of ADHD and autism assessments.
Health Secretary Yvette Cooper added: “Professor Fonagy’s review has shown the importance of early intervention to address mental health and neurodevelopmental conditions and the huge distress these can cause.”