The news comes as a United Nations-backed body, the International Narcotics Control Board, has drawn attention to the sharp increase in Ritalin consumption, especially in the United States.

But Chile seems to have its own Ritalin epidemic. “No other ‘pathology’ - not even winter flu - affects this many children,” says Dr Arturo Grau, a child psychiatrist, who heads the psychiatric unit at a Santiago children’s hospital.

Eighty per cent of the children referred to Dr Grau are there because teachers or parents suspect that they are suffering from Attention DeficitHyperactive Disorder.

Dr Bernarda Contreras, a paediatrician, says that she is frequently sent children as young as four whose parents or day-carers believe they have this neurological disorder. “I ask for a written report, before referring them to a neurologist,” she says. “Often . . . the teachers decide it is not worth the time.”

ADHD occurs in about 3-5 per cent of the school-age population, says Dr Grau, way below the estimated 25-30 per cent of children currently being treated in Chile. The symptoms - short attention span, erratic performance at school, difficulty following instructions, frustration and rebelliousness - are virtually indistinguishable from many other problems. While most children diagnosed for ADHD use Ritalin, children of low-income families use other stimulants.

Ritalin is “an excellent medication, but horrible for a person who doesn’t need it,” says Dr Grau. “Many children end up worse, like someone drinking 10 cups of coffee a day.”

Even more seriously, many of the children should not be taking Ritalin at all. Grau blames medical misdiagnosis, rigid teaching techniques that do not consider pupils’ attention spans and the extreme competitiveness of the school system for the overuse of the drug, which may depress appetite and growth and can cause hyperactivity in children when they stop taking it.

“Everyone’s convinced that children need medication in order to have good results at school and be successful,” Grau says.

Most teachers and paediatricians refer children suspected of ADHD to a neurologist, who is not an expert in child psychiatry - a relatively new discipline with only about 100 specialists in Chile.

“Anxiety syndromes and depression both tend to have identical syndromes to ADHD,” says Grau. He has found that many children respond as well, or better, to treatment based on placebos. The added attention - special letters to teachers, conversations with parents and solid advice on caring and teaching - seem to produce these results.

With class sizes around 40, it is hard for teachers to get to know each student. Dr Grau says that children’s attention span is about three minutes per year of age: “Five-year olds can concentrate for about 15 minutes,” says Grau. “But they’re supposed to sit still for 45.”

A 1995 study found teachers spend up to a quarter of their time disciplining their students. When a student is disruptive, the teacher typically refers him or her to a specialist, says Ana Maria Olguin, who has taught for 32 years.

Olguin, Grau and others say the pressures of Chile’s highly competitive economy have altered family life, so that children often don’t get the support and rest they need.

Chile has one of the highest rates of family violence in the world. The drive to get ahead means parents struggle to get their children into the most prestigious schools. Many children travel an hour or more to reach school by 8am.

In its 1995 report, the INCB urged all governments “to exercise the utmost vigilance in order to prevent ‘overdiagnosing’ of ADD in children and medically unjustified treatment with methylphenidate [the non-proprietary name for Ritalin] and other stimulants.”