Attention deficit hyperactivity disorder, or ADHD, is one of the commonest psychiatric disorders in childhood, and the most common drug used to treat it is methylphenidate. Cochrane reviewers published the most comprehensive review of the evidence on its effects in November 2015 and the lead author Ole Jakob Storebø, a senior researcher from Psychiatric Research Unit, Region Zealand, Denmark, tells us what they found.
John: Attention deficit hyperactivity disorder, or ADHD, is one of the commonest psychiatric disorders in childhood, and the most common drug used to treat it is methylphenidate. Cochrane reviewers published the most comprehensive review of the evidence on its effects in November 2015 and the lead author Ole Jakob Storebø, a senior researcher from Psychiatric Research Unit, Region Zealand, Denmark, tells us what they found.
Ole: ADHD affects approximately one child in every 30 under the age of 12, and causes problems with attention, hyperactivity, and impulsivity. It impairs their functioning or development. We investigated whether methylphenidate, which is better known as Ritalin or Concerta is beneficial or harmful for the treatment of ADHD in children and adolescents, and have found that much uncertainty remains even though methylphenidate has been used for the treatment of ADHD for over 50 years.
For our review, we searched for randomized trials that had compared the drug with placebo or no intervention in children and adolescents and had looked at the effects on ADHD symptoms, serious adverse events, non-serious adverse events, general behaviour and quality of life. We found a very large number of studies, with 38 parallel group trials and 147 crossover trials in which the patient acted as their own control. These 185 studies included a total of more than 12,000 patients whose average age was just under 10.
Our analysis of the parallel group trials suggests a beneficial effect of methylphenidate on teacher rated symptoms, general behaviour and quality of life; with no evidence that methylphenidate increased serious adverse events. However, there was sparse data on this outcome and we cannot rule out serious adverse events based on the randomized trials. Methylphenidate was associated with an increased risk of non-serious adverse events.
In summary, we cannot be certain about the size of the effects because of the risk of bias in the included studies, and the very low quality of the evidence on the outcomes. The evidence is not strong enough to provide a definitive guide for practice. The median duration of drug treatment was less than two months and few trials lasted more than six months, which means that we can conclude little about the benefits and harms of methylphenidate use for longer than six months. Our findings are therefore in disagreement with published guidelines and meta-analyses, with many recently published reviews and guidelines claiming large beneficial effects of methylphenidate. The reviews and meta-analyses have several methodological shortcomings and many have not assessed harms. With that in mind, we are now systematically reviewing adverse event data from observational studies, which might provide information on the harms of methylphenidate when it is used for longer periods and we hope to publish this review by the end of 2016.
John: If you would like to find out more about the information that Ole Jakob and his colleagues were able to find in the randomized trials of methylphenidate, you can find their full review at Cochrane Library dot com, with a search for 'adhd and methylphenidate'.