Hektoen International

A Journal of Medical Humanities

Going berserk

Howard Fischer
Uppsala, Sweden


Berserk: frenzied, furiously, or madly violent.
– Oxford English Dictionary


A yelling man is about to attack with a large club.
Imaginative drawing of a berserker in a fur loincloth. From Den Skandinavska Nordens Historia (The Scandinavian North’s History) by Gustaf Henrik Mellin, published 1850. The British Library on Flickr via Norwegian Wikipedia. No known copyright restrictions.

The word berserkr in the original dialect probably meant “bear-shirt” because the berserkers fought wearing only bear skins.1,2 The bear, not the lion, was the “king of the beasts” in Europe until the Middle Ages. Dressing in bearskin and acting like a bear was a mark of status. The oldest known statue, about 20,000 years old and found in Southwest France, represents a bear.3 Before going to battle, berserkers would perform ritual dances and drink bear’s blood.4

While fighting, they would howl, foam at the mouth, and bite the edge of their shields. They believed that they were invulnerable to fire and to penetrating steel weapons, but not to clubs or hammers. In early Scandinavian sagas and poems, they are portrayed as bodyguards and elite soldiers. Later they are shown as wild men who loot, plunder, and kill indiscriminately. The earliest surviving reference to them is from the ninth century. In North America, continental Europe, as well as in Scandinavia, there are legends of “wolf-warriors” dressed in wolf skins. These were also known as berserkers in Scandinavia. Having attained a state of frenzy, the men would shiver, their teeth chattered, their face would appear swollen, their color would change, and they would become enraged.5

How did they get into such a state? Suggestions include self-induced hysteria, marijuana, and alcohol.6 Alcohol, however, was generally taken to induce a state of unconsciousness. More probable are several psychoactive substances. “Performance-enhancing drugs” have long been used by armies before combat: the Incas chewed coca leaves, Mexicans smoked marijuana, opium was used by Turkish soldiers, and both sides fighting in World War Two provided amphetamines to their armed forces.7 It has long been thought that the berserkers ingested the mushroom Amanita muscaria before battle. This pretty, red-and-white mushroom has been used in Siberia as an intoxicant, possibly in association with religious rituals. It is also known as “fly agaric,” either because it was used in the Middle Ages to attract and kill flies, or because it was believed that flies were in the heads of insane or bizarre persons.8

A. muscaria is poisonous, but in small amounts is hallucinogenic. Its active ingredient mimics the effect of serotonin on the brain, producing euphoria, repetitive actions, feelings of increased strength, and visual hallucinations.9 High doses will produce trembling, delirium, and seizures.10 The North American Mycological Association points out that there have been “no reliably documented deaths from…these mushrooms in the past 100 years.”11 We also have this anecdote: “During a march… in 1814 a Swedish officer noticed that some of his men…[had] wild raging…[and] foaming at the mouth.” They had eaten A. muscaria to put themselves in a “fighting mood.”12

The other contender to produce the berserk state is the flowering plant Hyocymus niger, also known as henbane. It is part of the family of Solanacea, which includes potatoes, tomatoes, peppers, and Datura stramonium, or jimson weed. Like Datura, H. niger contains anticholinergic alkaloids, and has been used as an anesthetic. Ingestion produces increased strength, a red face, delirium, twitching, but also aggressive rage. It lowers blood pressure, which might mean that an intoxicated, wounded person would bleed less. There is also decreased pain perception. A pouch of H. niger seeds was found in a Viking grave in Denmark.13

In Beowulf, “the oldest of the long great poems written in English,” the eponymous hero kills the monster Grendel. There is some suggestion that Grendel may be a berserker, based on his resemblance to an animal-like monster, his rage, and his invulnerability to fire or sharp, penetrating weapons.14,15

As the North adopted Christianity, the Church there sought to eliminate traces of paganism, including the bear cult. The bear was made into an enemy of Christians, sometimes even a tool of the Devil.16 In 1123, Icelandic Christian law banned the berserkers and their cult.17,18



  1. Berserker. Wikipedia.
  2. NA. Berserkers, National Museet Danmark. en.natmus.dk
  3. Jay Smith. “Review of ‘The Bear: History of a Fallen King,’ by Michel Pastoreau,” J Modern History, 85(2), 2013.
  4. Phil Gibbons. “Crazy facts about Viking berserkers, history’s extreme Norse warrior-shamans,” 2020. ranker.com
  5. Berserker. Wikipedia.
  6. Madison Margolin. “Did berserkers take psychedelic drugs? The Viking warriors explained,” Netflixtudum, 2022. netflix.com
  7. NA. “Better fighting through chemistry? The role of FDA regulations in crafting the warrior of the future,” [Third year paper], 2004. dash.harvard.edu
  8. Jennifer Ouelette. “How Vikings went into a trancelike rage before battle,” WIRED, Sept 21, 2019. wired.com
  9. Sara Gorham. “Darling amanita,” Agni, 67, 2008.
  10. Ouelette,”Vikings.”
  11. Amanita muscaria. Wikipedia.
  12. dash.harvard.edu,”Chemistry.”
  13. Ouelette, “Vikings.”
  14. Christie Ward. “Grendel and Berserkergang,” Lambda Alpha J, 40, 2010.
  15. Meyer Abrams, ed. The Norton Anthology of English Literature, sixth ed., New York: W. W. Norton and Company, 1993.
  16. Smith, “Review.”
  17. Michael Speidel. “Berserks: A history of Indo-Europeans warriors,” J World Hist, 13(2), 2002.
  18. Abrams, Anthology.



HOWARD FISCHER, M.D., was a professor of pediatrics at Wayne State University School of Medicine, Detroit, Michigan.


Spring 2022  |  Sections  |  History Essays

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