Sam Cook has been on medication since his attention deficit hyperactivity disorder was diagnosed three years ago. The ten-year-old from Hitchin, Hertfordshire, takes Concerta, a slow-release type of methylphenidate, once a day.

“We noticed a change almost straight away, and the school did as well,” his mother, Sarah, said. “He used to be disruptive in class and upset other children. We tried a lot of things, taking him swimming to tire him out for example, but Sam is like a whirlwind, a Duracell bunny, and sometimes I cannot control his energy. He cannot keep still.

“The medication doesn't change him - he is still full of energy - but it takes that edge off him and makes him easier to manage. You can get through to him when he is on the medication.”

Ms Cook said that she had noticed a few side-effects from the drug. Sam was a bit more anxious than he used to be and his sleep had been disrupted slightly.

“It can be tough, but the medication has been good and it has made a massive difference. He is actually learning things at school and you can get through to him. The drug makes him more manageable,” she said.

Ms Cook said that she would continue to use drugs to treat her son's ADHD, and would pay for them privately if necessary. Not using the medication, she said, “is not a road that I would even think about going down. It is not just Sam that is affected by his behaviour - it is everybody in that classroom. He was not able to deal with a classroom situation.”

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