13 Oct, 08 | by Steven Reid, Evidence-Based Mental Health
The benefits of St John’s wort (SJW) have been widely reported this week following the publication of this study. It’s not, as some articles suggest, a new trial but actually an update of a Cochrane systematic review and meta-analysis. The review is comprehensive, with the addition of some big recent RCTs, and the authors have restricted the inclusion criteria to major depression. The results reinforce those of earlier reviews: SJW is as effective as standard antidepressants in mild and moderate depression with the benefit of fewer side effects.
Perhaps the most interesting finding is that studies from German-speaking countries show much more favourable results. In fact taking out the German studies from the meta-analysis removes any benefit of SJW over placebo. It’s not easy to explain this difference – you can insert your own cultural jokes here. What is notable is that the German trials predominantly recruited from private practices in primary care with a long tradition of prescribing SJW. This contrasts with the remainder where studies were carried out in academic or hospital settings where SJW is not licensed as a drug. Despite matching inclusion criteria there may have been differences between the types of patient entering the trials (selection bias). Andere Länder, andere Sitten.
So given this ‘natural’ alternative why don’t I recommend SJW to people I see with depression? Well in the UK it’s not licensed as a medicine but sold as a dietary supplement, and comes over the counter in a variety of formulations: pills, potions, lotions – you might even to able to smoke it. That means it can be difficult to know what you are getting and dosages in this review varied from 240 to 1800 mg per day. The active ingredient and mechanism of action is still unknown – not that we really understand how standard antidepressants work either. The other concern is the potential for drug interactions. SJW stimulates those liver enzymes that break down medicines such as warfarin, HIV drugs and oral contraceptives rendering them ineffective. Combining it with other antidepressants can also have nasty effects: I had a near miss with a woman starting on the antidepressant sertraline, who hadn’t admitted to SJW use as it was a ‘herb’ she was taking for migraine. So it may be a plant extract but it is certainly not innocuous.