Washington

The potential link between antidepressants and suicidal behaviour in children has been given further substance by a study from the US Food and Drug Administration (FDA).

Children and adolescents on antidepressants called selective serotonin reuptake inhibitors are 1.8 times more likely to experience suicidal thoughts or behaviour than those who do not take the drugs, the FDA said on 20 August. The analysis, by Tarek Hammad, an FDA safety reviewer, rests on drug-company data from 25 clinical trials.

The study confirms earlier findings by Andrew Mosholder, an epidemiologist at the FDA, who produced an analysis of the data in February but was banned from presenting his results in public. The FDA said at the time that the findings were only preliminary, but news of the suppression fuelled fears that data on the drugs were being withheld by drug companies and government regulators.

Mosholder's analysis put the risk only slightly higher, at 1.9 times greater for children on the drugs. But unlike that study, Hammad's analysis did not find a significantly higher risk for the subgroup of children with serious depression.

The risk also varied for the nine drugs studied. Fluoxetine, marketed as Prozac, did not increase the risk of suicide. Others, such as venlafaxine (Effexor), were linked to a significantly higher risk of self-harming thoughts and behaviour.

The analysis increases the pressure on the FDA to further discourage doctors from using the drugs ‘off-label’ — prescribing them in cases for which they are not approved. Of the nine drugs in the study, only fluoxetine is specifically approved to treat childhood depression. The FDA has already asked makers of the drugs to use labels warning that adults and children on the medication must be monitored for suicidal behaviour, but two advisory committees will meet next month to discuss whether more should be done.

The data used in the study are largely unpublished, leading to renewed calls for the government to require drug makers to release results from clinical trials. “Mosholder's initial findings have been confirmed and reconfirmed,” says Senator Chuck Grassley (Republican, Iowa). “When there are known risks with a drug, the information must be made available in a timely way.”