Since the Salem witch trials happened in 1692 and 1693 and took the lives of at least 19 people, they've been an American obsession.

What if there were a theory to explain that most inexplicable of tragedies? And what if that theory involved baking?

That's the spooky idea Linnda R. Caporael floated in her 1976 paper Ergotism: The Satan Loosed In Salem. In search of a concrete explanation for the witch-hunting mania, she stumbled upon a theory so wild it just might be true: A fungus in bad bread caused the symptoms of "witchcraft" that drove Salemites to persecute one another.

She pegged ergotism as the culprit. It's a condition that results from a fungus that grows on rye. It looks like overbaked grain:

But its effects are much more serious. If people ingest it, they can develop gangrenous ergotism (which causes the limbs to fall off) or convulsive ergotism (which can include convulsions, choking, pricking, and even hallucinations). That tipped off Caporael, since those symptoms sounded similar to the ones reported by people who'd fallen prey to "witchcraft" in Salem.

The best case that the Salem witch trials were caused by bad bread

There are other medical theories for the Salem witch trials Ergot isn't the only medical explanation for the Salem witch trials (though, like ergotism, these explanations are on the fringe for historians). Some say that a slave, Tituba, dosed girls with jimsonweed that caused them to experience symptoms of witchcraft, while other theories propose that encephalitis lethargica (the sleeping sickness featured in the film Awakenings) may have been present in Salem.

Without a doubt, the theory is controversial (more on that later). But Caporael and later supporting scholars, like Mary Matossian, present a compelling case that a fungus was among the people of Salem.

On an agricultural level, the growing conditions were right for ergot to flourish — a wet season in 1691 would have been perfect for ergot to spread on the rye. In addition, Salemites were unlikely to have known what ergot was, and Caporael found later letters that showed ergot was a significant problem in the area.

Social conditions back up the theory too. Caporael notes that it's likely the minister was paid in grain from the western part of town, and his daughter and niece were some of the first to be "afflicted" by a witch's symptoms. Moreover, the afflicted (those who might have suffered ergotism) were concentrated in the western part of town, where ergot was likely to have flourished.

Finally, and perhaps most important, the effects of a "witch's curse" matched well with convulsive ergotism's symptoms, now documented in the online archives of Salem records.

The most intriguing symptom involves a thoroughly modern drug. LSD — the familiar hallucinogenic — was first synthesized from ergot in 1938. It would be wrong to imagine Salemites as paper-dot-popping day trippers due to bad bread, but some symptoms of ergotism do resemble LSD (albeit in lower intensity). Villagers' reports of quivering lights in the distance sound similar to LSD's effects.

It's a compelling idea: All those witch accusations were due to a few bad trips. But there are also some people who think it's about as realistic as a flying broomstick.

The best case that the Salem witch trials weren't caused by bad bread

The most common political explanation for the trials Historians can spend their entire careers combing through archives and developing a unique theory about Salem, so there are many stories about the crisis. Picking a common one, however, leads you to something like a less sexy version of the classic play The Crucible. It is, roughly speaking, the picture painted in books like Salem Possessed: Salem was a community riven by political disputes between Salem Town and Salem Village, as well as by the polarizing minister Samuel Parris. As disputes over Parris's payment and function intensified, the "witchcraft" afflictions appeared in his house. Though it's not often explicitly stated, the theory might be that he had his daughter and niece fake "affliction," and this exacerbated existing political fissures between the town and village, causing a wave of accusations, "afflictions," and trials.

Caporael's theory is, for the most part, fringe, especially in historical circles. Though many in the sciences have cited her landmark paper (as well as many in the media), it's largely ignored in historical studies of Salem. The most vocal objectors said she wasn't merely misgiven, but just plain wrong.

Nicholas Spanos wrote two papers arguing that Caporael's theory was bunk (he's been joined by other scholars, like Alan Woolf). Spanos's objections are numerous, including, at base, that some of the reported symptoms didn't match the symptoms of ergotism. For example, bruised skin is common but is hard to find in the records.

Spanos also pokes holes in Caporael's claims that the Salem witch trials were an isolated event, noting smaller witch trials in neighboring historical towns. And he's explicit in the implications for Caporael's theory:

Understanding the demonic enactments, the pattern of accusations, and the legitimation of those accusations that occurred at Salem requires that these events be viewed as part of a sociopolitical drama that was played out in terms of the implicit worldview and explicit religious assumptions that held sway among seventeenth-century Puritans. The ergot hypothesis neither fits the facts of the case nor, in any way, helps to elucidate those facts.

Ergotism has probably affected some towns. We may never know about Salem.

Caporael didn't pull her theory out of nowhere — she was inspired by a 1951 mass poisoning in Pont-Saint-Esprit, France, that's widely attributed to an ergotism outbreak (though conspiracy theorists now claim it was part of a CIA experiment with LSD). Other scholars have attributed many cases of mass hysteria, like the Dancing Plague of 1518 and many of the European witch trials, to ergotism. It's even known as Saint Anthony's Fire, after an order of monks who treated the widespread disease in medieval times (though they were probably often cases of gangrenous, not convulsive, ergotism).

Even with historical precedent, there's only so much we'll ever know about ergotism, especially in Salem. We can't do a forensic examination of a 300-year-old piece of bread. Though historians generally eschew a scientific explanation for the crisis, there's no firm consensus on what caused the witch trials in Salem.

There's also something fundamentally magical about the current historical explanations for the Salem witch trials. Many ergotism skeptics, like Spanos, blame "mass hysteria" and boundary disputes for the witch accusations, casting Salem as a victim of particularly vicious gossip. Others blame social dynamics among teenage girls, as if 1600s Puritan Salem were Heathers or Mean Girls. It's possible to see some commonality between mass hysteria and the idea of possession — they're two explanations without an identifiable catalyst in the real world.

Caporael, whose original paper is modest in its conclusions, gestures toward a third way: Perhaps a medical explanation provided a vehicle for the fervor. Maybe ergot was responsible for a few of the symptoms, but Salem's Puritan mania and political divides turned a few real cases into a witch-hunting epidemic. There's a reason her paper wryly proposes that "one Satan in Salem may well have been convulsive ergotism."

Ultimately, how you perceive the Salem witch trials might depend on which threat you fear more. If you don't want to believe that a community could be destroyed over petty land disputes alone, than ergot helps the trials make sense. But if you don't like thinking society can crumble because of a few loafs of fungal bread, then you'd lean toward a social explanation of the trials.

Either way, it's perfect for Halloween: No matter which theory you believe explains the trials, the outcome is still frightening.