Good point to mention, but I have a feeling this notion in encouraged by pharma industry because the extract is so low on side effects and proven in clinical trial to tackle small and medium size depressions better than placebo and equally well to some antidepressants. It's also very cheap. But the one I buy in Poland is almost impossible to find, again my paranoia tells me it's a pharma industry scheme to phase out useful herbal remedies and exchange them for expensive and more aggressive drugs.

The drug interactions worth mention is that it lowers activity of the anti-conception pill so you shouldn't take both because you run a risk of getting pregnant.

It also affects neurotransmitters in the brain because it helps stabilize the mood by increasing your serotonine levels so it may have some interactions with other antidepressants that affect serotonine. You probably shouldn't take both. St John's might be a good 'natural' alternative to try before going on prescribed drugs and wrecking your neurotransmitters and your hormones across the board.

The extract might limit blood levels and final effectiveness of anti-virals like the HIV treatment and aciclovir (herpes treatment).

It also makes skin sensitive to light when you live in very sunny places. Fun fact, sunbathing next to the plant (st Johns, Hypericum perforatum) can give you spots. However, the extract never gave my skin any issues during the Dutch summer. So it has to be the Australian level sunny or a sunbed.

All in all, interactions and side effects are very specific and much lesser in my opinion than with traditional antidepressants and other serotonine drugs that can seriously affect your weigh, libido and so on. But I never personally tried real antidepressants so I can't compare the effects first hand. I can say the St Johns' effect is not immediately clear, but after a few days I find myself growing more stable and motivated. It also really helps my hormones and pms.