Iboga root, central to several Gabonese ritual traditions, is believed to have huge potential for use in treating addiction and some mental illnesses

The temple is dark, its sandy floor edged with candles. People sit shoulder to shoulder beneath palm fronds hung from the rafters. Through the night, they swallow what they have come here for: a bitter root bark called iboga.

Tabernanthe iboga is a slow-growing central African rainforest shrub, the root bark of which has long been used in several Gabonese ritual traditions.

Experts peel back the evidence to see whether any of the health claims about vitamin patches stick – or whether it’s the placebo effect at work

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Feeling fatigued and listless? Searching for an energy boost? Want to improve your mood and motivation? The solution may be, according to a proliferation of online articles and wellness TikToks, not to seek medical advice but to whack on a vitamin patch.

Wearers purport to feel more focused or energised when adorned with the patches, some of which look like transparent squares, and others which are cuter and more colourful, resembling stickers or temporary tattoos.