Conversely, Ritalin (methylphenidate), a cocaine-like drug, is used as an antihyperactive drug in children, but produces a stimulant effect in adults.

Without adequate studies, it is left to postmarketing surveillance, when it exists, to turn up adverse effects. The results are often distressing.

Recent reports have raised concerns that SSRIs may be associated with an increased risk of suicide in children. Two of these - venlafaxine (Efexor) and paroxetine (Seroxat/Paxil) - have recently been banned for children because the risk is so great. Last September, the UK Committee on Medicines announced a ban on Efexor. Only months earlier, Seroxat was similarly banned for children in the UK, Canada and Ireland.

In both cases, previously concealed evidence from controlled clinical trials conducted by the drugs’ manufacturers, Wyeth and GlaxoSmithKline, respectively, had shown that children taking SSRIs were driven to acute emotional distress, leading some to become suicidal or homicidal.

Only when this concealed information had been uncovered did healthcare providers receive letters from the manufacturers confirming that the drugs caused an increase in problems such as aggression, suicidal thoughts and attempts, and self-harm rates by up to 3 per cent.

Newspaper reports suggested that both drug companies knew for several years that their products could be causing children to feel murderous and suicidal (see www.guardian.co.uk/uk_news/story/0,3604,1045902,00.html).

The manufacturers were able to conceal these effects in their own studies by describing the intense emotional distress and violent behaviour of the children taking the drugs as 'emotional lability', a euphemism not uncommon in clinical research that should have, but didn’t, raise alarm bells for drugs regulators.

The increased risk of suicide among young children is not new. In one study carried out by Yale University, 14 per cent of young people aged 10 to 17 developed tendencies towards, and thoughts of, self-injury while taking fluoxetine (J Am Acad Child Adolesc Psychiatry, 1991; 30: 179-86). This effect has been noted in adults as well (Am J Psychiatry, 1990; 147: 207-10).

While Efexor and Seroxat are no longer recommended for children, the suicide risk has not gone away. A review by the US Food and Drug Administration (FDA) of 20 placebo-controlled trials, involving over 4100 children and adolescents prescribed one of eight antidepressants - citalopram, fluoxetine, fluvoxamine, mirtazapine, nefazodone, paroxetine, sertraline and venlafaxine - conceded that these were all more likely than a placebo to cause suicidal thoughts.

Adding insult to injury, the FDA also concluded that there was no evidence that the drugs were effective in treating childhood depression.

Pfizer, the manufacturer of sertraline (Lustral/Zoloft), was quick to distance itself from the review by recently funding a study of 376 depressed children (aged 6-17) that found that sertraline was 'effective and well-tolerated' - despite the fact that 17 of the children withdrew from treatment because of an adverse effect, and that two attempted suicide (JAMA, 2003; 290: 1033-41).

In the face of overwhelming evidence, the UK’s Medicines and Healthcare Products Regulatory Agency finally banned the prescription of SSRIs to under-18s in December 2003, although the practice continues elsewhere in the world.

Developmental damage Whether the use of antidepressants and stimulants leads to addiction later in life is also poorly studied. Although recent evidence suggests childhood use of stimulants like Ritalin does not lead to stimulant addiction in later life (J Clin Psychiatry, 2003; 64 [Suppl 11]: 9-13), there’s a catch. These studies generally look for physical, not psychological, addiction.