Sir

Sahakian and Morein-Zamir's reference to attention-deficit hyperactivity disorder (ADHD) as heritable and affecting 4–10% of children worldwide is contentious (Nature 450, 1157–1159; 2007). The claimed incidence of ADHD varies strikingly over time: less than 0.1% in the United Kingdom before 1990, and now generally claimed to be between 1% and 5%. This variation is equally dramatic by country: highest in the United States, followed by Australia and Iceland, but low in Italy, for instance.

The diagnosis is in many cases questionable, and evidence for its heritability is shaky except in highly selected groups. The marked increase in the number of prescriptions of methylphenidate (Ritalin) — from 2,000 a year in 1991 to more than 300,000 in the United Kingdom today — says more about fashions in the diagnosis and treatment of naughty, inattentive or badly parented children than it does about a genuinely heritable 'disease.”

In the United States, the Federal Drug Administration has called attention to the 'epidemic' of schoolyard Ritalin use. As Sahakian and Morein-Zamir note, there is disturbing evidence of long-term, adverse sequelae associated with the use of such amphetamine-like drugs, especially on young and developing brains.

The assumption behind the cognitive-enhancer debate is that users are essentially making free choices about whether or not to take risks. But children being prescribed Ritalin are being drugged as a method of social control.

That, it seems to me, is a real ethical issue. If we don't recognize the real-world situation in which drugs are bought, prescribed and used, then the ethical debate is vacuous.