A year 12 student from Ryde Secondary College said mixing crushed Ritalin in energy drinks was common among his peers "to get a good boost during tests". He tried the mixture while studying for his trial exams earlier this year, and said that it drastically increased his word rate. "I was set to write around 2000 words but at the end I noticed I had written over 9000," he said. Students asked each other whether or not they sat the exams "natty" (naturally), he said. He said the Ritalin costs $5 to $10 a pill. Students generally mix two to three with energy drinks, and also report snorting it.

"Usually a student who is prescribed it sells them to get some extra money," the student said. A student from Normanhurst Boys High School says he and many of his peers have tried Concerta, which is also used to treat ADHD. Five of his friends reported using the drug regularly. "It pretty much keeps you focused and on task for whatever you're doing," he said. "It makes it really easy to pump out hours of study without a break because your mind doesn't start wandering or getting tired.'' Another student who spoke to The Sun-Herald has been diagnosed with ADHD, for which he has been prescribed Concerta. "But when I need to study longer I up my dosage, which does wonders," the student, from Mosman High School, said.

''I have spoken to some of my friends about letting them try some of my ADHD medication but most are too scared of what could happen.'' He said he had also taken ''dex'', or dexamphetamine, also prescribed to people with ADHD, while studying but used it sparingly because it was "a harder drug". The latest Medicare data available shows about 24,000 people under 19 were on ADHD medications in NSW in 2010. And nationwide statistics show prescriptions for all stimulants used to treat ADHD rose 87 per cent between 2002 and 2009, while prescriptions for the drug commonly sold as Ritalin rose 300 per cent. Almost 70,000 HSC students across the state will sit the English paper tomorrow, which is the start of the four-week written exam period.

Jayne Lucke, a researcher specialising in the use of pharmaceutical stimulants by healthy people, suspects the increase in prescriptions is because it is easier to obtain the medicine and people are more comfortable with the idea of taking it for a non-medical reason. But, while she is not surprised by reports of the drugs being used by students, Ms Lucke said without any official Australian research, it would be unwise to speculate about the prevalence. ''But if this is being talked about, perhaps it is a common thing that we should investigate more," the researcher from the University of Queensland's Centre for Clinical Research said. Lee Sutton, a paediatrician, said taking ADHD drugs for non-medical purposes was dangerous and potentially lethal. "That's why drugs are prescribed, because they are not suitable to buy over the counter," she said.

Medical complications associated with misused stimulants can include loss of appetite, seizures, cardiac arrhythmia and psychotic episodes. Dr Sutton said stories of students combining Ritalin with caffeinated energy drinks were of particular concern. "All it's going to take is one kid who may have some congenital [heart] abnormality … to take this combination and then they drop dead. Of course, that's not going to be common but, nevertheless, it's risky," she said. Dr Lucke said that there were a number of ways students could get their hands on the medication - getting a prescription from a sympathetic doctor, buying it from those with legitimate prescriptions or obtaining via the internet. The Sun-Herald sought comment from the various schools of the students spoken to via the NSW Education Department, which notified the schools mentioned.

They responded that there was no evidence of the pervasive use of illegal stimulants in any of them. "[The principals] will speak to their schools' counsellors and offer any students concerned additional medical support if required," a spokeswoman for the department said.