Treating children who have Attention Deficit Hyperactivity Disorder (ADHD) with drugs has no advantage over other treatments in the long term, research has shown.
A study obtained by the BBC's Panorama programme says drugs such as Ritalin and Concerta work no better than therapy after three years of treatment.
The findings by an influential US study also suggested long-term use of the drugs could stunt children's growth.
The Multimodal Treatment Study of Children with ADHD has been monitoring the treatment of 600 children across the US since the 1990s.
In 1999, the American study concluded that after 14 months, medication worked better than behavioural therapy for ADHD.
The study now concludes that this advantage is lost after 36 months.
Most of the estimated 500,000 children in Britain with ADHD receive no treatment at all.
But of those that do, most - about 55,000 last year - are prescribed stimulants like Ritalin and Concerta.
The cost of these drugs to the NHS is about £28m.
The National Institute for Clinical Excellence is currently revising the treatment guidelines for ADHD.
Panorama: What Next for Craig? BBC One 8.30pm, Monday, 12 November 2007
Correction February 19 2010: Following a ruling by the BBC Trust, this report has been amended and some material removed. Details of the Trust's finding can be
The Panorama programme was also the subject of a ruling by the BBC's Editorial Complaints Unit, which can be