St John's wort is better tolerated than a traditional antidepressant in cases of mild to moderate depression, according to a recent study (BMJ 2000;321:536-9).

Three hundred and twenty four outpatients in Germany took either the extract of the herb St John's wort (Hypericum perforatum) or the tricyclic antidepressant imipramine, one of the most frequently prescribed antidepressants. The two drugs had the same therapeutic value. But only 39% of the patients taking St John's wort suffered from any side effects, compared with 69% of those taking imipramine.

Side effects of antidepressants include dry mouth, sweating, nausea, weakness, and headache. In the study, 3% of patients stopped treatment with St John's wort because of its negative effects compared with 16% of those taking imipramine.

"The results of this study support the conclusion that the two treatments are therapeutically equivalent," says Helmut Wolke, the author of the study. "Hypericum should be considered for first line treatment in mild to moderate depression, especially in the primary care setting."

St John's wort is grown and used throughout Europe, north America, and elsewhere, can be traced back to the ancient Greeks. Its value as an antidepressant has been suggested before, but until now few studies have established whether it is as effective as traditional forms of medication.

Earlier this year the Medicines Control Agency issued a warning that St John's wort should not be taken by women using oral contraception or by patients being treated for HIV or depression. It is believed that the herb interferes with the action of these drugs. For the same reason the agency also advised patients taking warfarin, digoxin, or theophylline to seek medical advice before taking the herb. Scientists at Cambridge University are currently developing a synthetic version of the herb that does not have these interactions.