More research is needed to help doctors balance the risks and benefits of controversial ADHD drug Ritalin, a team of scientists says.
Even after 50 years of use, the quality of available evidence on Ritalin is poor, said the scientists who reviewed 185 studies involving children and teenagers prescribed the drug for attention deficit hyperactivity disorder.
They found that Ritalin, the best-known brand name of the drug methylphenidate, appeared to produce modest improvements in symptoms, general behaviour and quality of life.
There were also signs that children on Ritalin were more likely to experience sleep problems and loss of appetite.
However, the team from the Cochrane Library which publishes research intended to shape health policy, said it could not be confident about any of the results.
Co-author Dr Morris Zwi, consultant child and adolescent psychiatrist at Whittington Hospital NHS Trust in London, said: "This evidence is important for health professionals and parents of children with ADHD.
"Our expectations of this treatment are probably greater than they should be, and whilst our review shows some evidence of benefit, we should bear in mind that this finding was based on very low-quality evidence.
"What we still need are large, well-conducted trials in order to clarify the risks versus the benefits for this widely used treatment."
Dr Camilla Groth, from Herlev University Hospital in Denmark, said: "This review shows very limited quality evidence for the effects of methylphenidate on children and adolescents with ADHD. Some might benefit, but we still don't know which patients will do so.
"Clinicians prescribing methylphenidate must take account of the poor quality of the evidence, monitor treatment carefully, and weigh up the benefits and adverse effects."
ADHD is a behavioural disorder characterised by difficulty maintaining attention, impulsive behaviour and extreme hyperactivity.
The trials reviewed recruited more than 12,000 patients aged three to 18 mainly from the US, Canada and Europe. All compared Ritalin treatment with a dummy placebo drug or no intervention.
The Cochrane scientists pointed out that some of the results could have been distorted by bias. It might have been possible for people involved in the trials to know which treatment the children were taking, they said.
They also drew attention to incomplete reporting of results and inconsistent analysis.
