Thousands of Scottish children, some as young as six, are wrongly being labelled hyperactive and given controversial drugs to stop anxious parents thinking they are to blame for unruly behaviour, a leading academic has warned.

Dr Gwynedd Lloyd says doctors are wrongly diagnosing ADHD (attention deficit hyperactivity disorder) when many youngsters are just behaving badly as a normal part of growing up.

The Edinburgh University academic claims this is leading to "widespread abuse" of the controversial drug methylphenidate, commonly known as Ritalin, by doctors who over-rely on checklists when deciding on medication for children.

Ritalin, nicknamed the "chemical cosh", has been criticised amid claims it has dangerous side-effects, including abdominal pain, anxiety, dizziness, headaches and psychosis.

Lloyd, head of the educational studies department at Edinburgh University, claims that a lack of proper investigation by doctors and pressure from parents are leading doctors to diagnose ADHD inappropriately.

She said: "Our research shows that a lot of children are being categorised without evidence from school about their behaviour problems. There is no objective measurement for judging if ADHD is present. In many cases, decisions are being made on very general descriptions of behaviour. Some parents are even going private to get their children diagnosed."

Some 46,000 children are diagnosed as having the condition, with more than 9,000 eligible for drugs therapy, the Scottish Medicines Consortium reports. In the past year, 42,832 prescriptions were made for Scottish children with ADHD, an annual increase of 11.7%.

ADHD sufferers have difficulties with impulsiveness, lack of concentration and hyperactivity. The condition, which Lloyd accepts does exist, leads to tantrums and social clumsiness and is usually identified in early childhood.

However, in Lloyd's latest book, Critical New Perspectives On ADHD, which the child behaviour expert has written with two other academics, she argues many parents are looking for a quick fix when their child misbehaves at school.

She said: "Parents feel that the schools are blaming them when their child is behaving badly at school, but teachers do not have the time to deal with individual problems when they are teaching a class of 30 or more. Doctors think they are helping these families but they are actually clustering children together under a catch-all condition on the flimsiest evidence."

On the use of Ritalin, Lloyd added: "This kind of medication for children as young as six is crazy. Their brains are still developing and yet they are being given mind-altering drugs."

Disparities among Scottish health boards led the health standards watchdog, QIS Scotland, to launch an inquiry into Ritalin prescribing rates last year. NHS Fife is the largest single user of ADHD drugs, with 154.73 prescriptions per 1,000 population (aged six to 14) in 2004-2005. The average for Scotland in the period was 70.36.

Louise Brunton, from Glenrothes, whose son Aaron was diagnosed with ADHD six years ago, last night agreed with Lloyd that many parents wrongfully put forward ADHD as an excuse for bad behaviour.

Brunton, 34, who until recently was involved in a parents' support group, said: "Families would turn up and say that their son or daughter had ADHD, but they clearly didn't. They were just badly behaved. Some parents fail to acknowledge that their children can be bad and they are soft on discipline. It makes it harder for genuine cases of ADHD to be treated sympathetically by doctors."

Brunton, whose son was prescribed Ritalin but now uses Concerta, an alternative drug, added: "From a young age, Aaron did not have normal responses, his behaviour went well beyond misbehaving. He set fire to my old house twice and he has also flooded our home. He has no concept of danger."

However, Dr Chris Steer, a consultant paediatrician at Victoria Hospital, Kirkcaldy, said: "It is up to clinicians to diagnose ADHD, not academics or educationalists, but there are safeguards in place.

"The usual age for children being able to use medication [such as Ritalin] is school age. The aim is to improve their learning, not to sedate them. The drugs for ADHD have been thoroughly tested."

Eric Taylor, a professor at the Institute of Psychiatry in London, described Lloyd's views as "extreme".

He added: "ADHD is not easy to diagnose, as symptoms can be similar to other behaviour problems, but I am not aware of misdiagnosis being a problem in Scotland."