EXPERIMENTS on animals have lent support to claims that a drug used widely in the treatment of acne can cause depression.

Roaccutane is highly effective in treating serious cases of acne, but in recent years the drug has been implicated in causing serious side-effects, including suicidal behaviour. The packaging spells out these risks, but why it should have this effect has never been clear; nor has it been proven that the drug is responsible, since adolescents with severe acne may feel depressed anyway.

A team at the University of Bath and the University of Texas in Austin investigated the effect of Roaccutane on mice, and reports the results in Neuropsychopharmacology. “You can’t ask a mouse if it is depressed,” Sarah Bailey, of the University of Bath, said yesterday. “So we used two tests to model behaviour.” Both involved putting the mice under stress. In one, they were put in water and forced to swim; in the other, suspended by their tails.

Under these circumstances mice will normally swim, climb or thrash around to try to escape, interspersed with periods of immobility when they appear to be resigned.

A mouse that is depressed will spend longer in the immobile state than one that is healthy. So the team gave Roaccutane to adolescent mice in doses equivalent to those given to human adolescents, and found that the periods of immobility significantly increased. The conclusion, Dr Bailey said, was that Roaccutane tended to increase depression-related behaviour in adolescent mice.

The drug belongs to a class of chemicals called retinoids, which have an effect on the way genes are “read” by the body, and reduce the rate at which new brain cells are generated. Roaccutane has been shown to damage the foetus in the womb, and precautions are taken to ensure that it is not used by women who are likely to become pregnant. However, recent findings suggest that brain-cell generation may be important not only in foetuses but also in adolescents and even adults, Dr Bailey said. The suspicion is that Roaccutane may influence the system responsible for producing the mood hormone serotonin, lowering the levels.

The evidence on those given the drug suggests that perhaps only 5 to 10 per cent are vulnerable to the effect. But there have been suggestions that retinoids may be implicated in Alzheimer’s disease and schizophrenia, so understanding more about how they work could lead to new treatments.

Roche, the makers of Roaccutane, said in a statement: “While no causal link has been established between Roaccutane and either depression or suicide, we are constantly monitoring all available safety databases on Roaccutane worldwide.”

13 MILLION USERS

The World Health Organisation reports 720 cases of psychiatric problems arising from the use of Roaccutane, including 84 suicides and suicide attempts

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