There's good evidence that products containing preparations of the herb St John's wort (SJW) can be useful for the treatment of mild depression. Many studies looking at short-term use of SJW have found its better than a placebo and as effective as some antidepressants, with fewer side effects.
However, not all preparations containing SJW are created equal: the final product can vary according to the growing conditions for the herb, the plant parts used, time and method of harvest, extraction and other manufacturing processes, and storage.
The active ingredients in SJW aren't known exactly, nor is it known what levels of even the suspected actives are needed to be effective. This makes it difficult to create a standard for an effective preparation, although there are some guidelines for extraction processes and minimum levels of key components.
Complementary medicines in Australia haven't traditionally been subjected to the same level of pre-market evaluation for effectiveness as conventional pharmaceuticals, and post-market surveillance tends to occur on a random basis or when issues arise with particular products or manufacturers.
Yet consumers and health professionals interested in using SJW for mild depression need to be confident that products sold in Australian pharmacies, supermarkets and healthfood stores are equivalent to the effective products reported on in medical studies.
We took a look at SJW and the herbal medicines industry to determine what level of confidence we can place in its products. In particular, we were interested in the kinds of claims manufacturers are making, and the evidence they have to back up their claims. We also tested some products to try to check the levels of suspected active ingredients, although this wasn't quite as straightforward as we'd hoped - see Chemical conundrums
, for more.