This Hallucinogenic Plant May Have Been Used to Induce a Trance-Like Rage in the Vikings' Toughest Warriors

A caste of Viking warriors fought with such ferociousness and vigor that they were said to howl like wild beasts and even bite their own shields out of rage. It is said that they entered combat in a trance-like state—or, in Norse: "berserkergang"—and completely naked except for animal skins and, perhaps, a piece of horned headgear.

These warriors were called berserkers and accounts of them date back to the ninth century. Now, an ethnobiologist has proposed the source of their in-trance rage: a plant called henbane.

It is thought the English word "berserk⁠"—meaning "out of control; wild or frenzied"—derives from berserkers, and most likely comes from combining "bjorn" meaning "bear" or "berr" meaning "without armour" with "serkr" meaning "coat".

Writing in the Journal of Ethnopharmacology, Karsten Fatur from the University of Ljubljana, Slovenia, challenges traditional assumptions that the trance was induced by self-provoked hysteria, epilepsy, mental illness, large quantities of alcohol or—as most widely believed—a species of toadstool with hallucinogenic properties.

The mushroom, amanita muscaria, is toxic—but it is said that it can be consumed if treated properly. Indeed, communities in Siberia and central Asia have been known to use the fungi for its psychoactive properties, which induce feelings of euphoria, hallucinations, drowsiness, a red flush and muscle jerks among other things.

These symptoms mirror descriptions of berserkers during one of their trance-induced rages. This includes delirium, twitching, a change in color to the face and an altered state of consciousness followed by weakness.

UNITED STATES - CIRCA 1895: Amanita Muscaria Poisonous (Photo by Buyenlarge/Getty Images)

But Fatur argues the effects of henbane are a better match. What's more, it is much more common to Scandinavia than the amanita muscaria mushroom, he says.

Our knowledge of beserkers, accounts of which date back to the ninth century, is filled with holes and what we do know relies largely on first-hand accounts recorded in a handful of Norse myths and sagas. Even these do not necessarily agree on many details beyond their blood-thirsty rage.

A description of King Hálfdan's berserkers in Hrólf's Saga, for example, describes them like this:

"On these giants fell sometimes such a fury that they could not control
themselves, but killed men or cattle, whatever came in their way and did not take care of itself. While this fury lasted they were afraid of nothing, but when it left them they were so powerless that they did not have half of their strength, and were as feeble as if they had just come out of bed from a sickness. This fury lasted about one day."

According to historical accounts, the condition of these rages began with shivering, teeth chattering and a general chill. Then, face swelling and reddening, followed by an intense rage during which the beserkers could not tell friend from foe. When the rage subsided, the warriors were left weak and feeble, sometimes for several days at a time.

Henbane can cause feelings of delirium, inhibition loss and manic episodes—hence, the excess so often described in accounts of beserkers. It can also trigger visual disturbances, hallucinations, drowsiness and red skin, as well as dull pain—which would explain the apparent invulnerability of the warriors.

Henbane (Hyosciamus niger) , by Giglioli E., 20th Century, ink and watercolour on paper. Whole artwork view. Drawing of the flower of henbane. (Photo by Electa/Mondadori Portfolio via Getty Images)

Henbane use can create side effects long after the initial effects—or rage—wears off, which Fatur says amanita muscaria does not. But, as Jennifer Oullette at Ars Technica points out, it doesn't account for all symptoms like, for example, the chattering of teeth.

For now at least, henbane is another hypothesis to add to the list—alongside self-provoked hysteria, epilepsy, mental illness, large quantities of alcohol and, of course, amanita muscaria.