Its side-effect rate ran no higher than placebo across 35 trials
Across 35 trials and 35,562 people followed observationally. The review found its real harms were almost entirely interactions with other medicines.
What the study found
Side effects at placebo level, and that is what makes it dangerous
Across 35 trials and 35,562 people followed observationally, side-effect rates on St John's Wort ran no higher than placebo, and the national liver-injury database rates it unlikely to cause harm. The same review found its real harms were almost entirely interactions with other medicines.
The caveat · Not designed to catch interactions
The 35,562-patient figure comes from post-marketing surveillance never designed to detect interactions, which duly reported none. The review's searches stopped in 2003. Its conclusion is explicitly conditional on a doctor knowing the patient is taking it, which is the condition most over-the-counter use fails.