The number of prescriptions for drugs to treat attention-deficit hyperactivity disorder (ADHD) has shot up more than 50% in just six years, official figures show.

NHS prescriptions for methylphenidate drugs, such as Novartis' Ritalin, leapt from 420,000 in 2007 to 657,000 in 2012, a rise of 56%, according to the Care Quality Commission.

Over the same timeframe, private prescribing rose from just under 2,000 to just under 5,000.

Steve Tomlin, spokesman for the Royal Pharmaceutical Society, told SKY News that better understanding of the disease's states has led to more appropriate diagnoses and therefore treatment. 

In addition, the scope of treatment has recently been extended into adulthood in a NICE guideline, also increasing the number of prescriptions.

However, also fuelling the rise is thought to be a growing trend among students for so-called "smart drugs" believed to stimulate brain activity.

"We are aware of reports in the media and scientific literature that it is being abused as a 'smart' drug to improve cognitive function," the CQC said, but warned "the long-term risks of this practice are not known".

Abuse potential

And because of the possibility that methylphenidate could be "diverted and abused", the watchdog has recommend that its use should be "monitored carefully".

Consultant psychiatrist Professor Tim Kendall told BBC Radio 4's Today programme that the rise in ADHD drug prescriptions is concerning, because of the potential detrimental effects of treatment with methylphenidates, which can stunt growth in a child by up to an inch in just a year.

"I think there's also increasing evidence that it precipitates self-harming behaviour in children and in the long term we have absolutely no evidence that the use of of Ritalin reduces the long-term problems associated with ADHD," he said, but did stress that its "very difficult" to treat the condition in children "without using Ritalin as well".