Around 10pm at a summer solstice party somewhere in Canada on June 20, 2000, about 20 people swallowed glasses of water mixed with the powerful psychedelic LSD. A decimal place error caused them to take about 10 times more of the drug than they thought they were getting. For the 12 hours that followed, they would ride out one of the most intense experiences of their lives, one that would change them forever.

Gram for gram, LSD is more powerful than most recreational drugs. While most substances like MDMA or cocaine are active at the milligram scale, the effects of lysergic acid diethylamide manifest at the _micro_gram scale—or one millionth of a gram. An average hit of LSD is 100 micrograms.

A trip can sometimes last 12 hours or more, pumping up heart rate, intensifying colors and sounds, and altering the perception of time. Because the LSD molecule, which mimics serotonin, has a “lid” that locks into serotonin receptors, it can remain there for hours. This is how low concentrations of the drug can be so potent.

Because of this sensitivity, it can be easy to overdose on LSD. But what happens when people take extreme amounts of LSD? This is the subject of a new report co-authored by Mark Haden, the executive director of MAPS Canada and an adjunct professor at the University of British Columbia, which looked at extreme cases of LSD consumption, revealing some bizarre health outcomes.

One of the cases covered in Haden’s study was that of a 15-year-old girl with bipolar disorder. She was one of the 20 people who accidentally OD’d on acid at the summer solstice party in Canada. She took a whopping 1,100 micrograms. For the next six hours, her behavior became erratic. She lay on the floor in the fetal position tightly clenching her arms. Her friends thought she was having a seizure and called an ambulance, although no one was sure if she was actually seizing, lost consciousness or was just lost in the overwhelming experience.

The next morning, her father visited her in the hospital. She told her dad, “It’s over.” He thought she meant the acid trip. She clarified that no, her bipolar illness, which had caused daily major episodes, seemed to be cured. A week later, her symptoms had still not returned. Doctors followed her progress for over a year, and nearly two decades later, she still hasn’t experienced episodes of depression or mania outside of postpartum depression. Looking back on the overdose, she said it felt like her brain chemistry had somehow been “reset.”

Haden says he was not only amazed that her symptoms resolved, but that such a high dose could ultimately be a positive experience. In his report, published in the Journal of Studies on Alcohol and Drugs, Haden also includes the story of another individual at that infamous solstice party, a 26-year-old woman who only took half a glass (approximately 500 micrograms) of LSD. Unbeknownst to her, she was two weeks pregnant. Yet she experienced no pregnancy complications and her son, now 18 years old, is a perfectly healthy bright young student.

The most remarkable case study included in the report is the 2015 story of a 46-year-old woman, who Haden calls CB, who had chronic pain caused by Lyme disease. CB snorted a line of white powder she thought was cocaine. Fifteen minutes later, she realized something was wrong and called her roommate, who told her what had happened: She had inhaled part of his stash of LSD.

While LSD usually comes in a “blotter” form—tiny pieces of paper dabbed with scentless, clear liquid acid—the drug can also come in a potent white powder form, and is not hard to confuse with other powdered drugs. CB’s roommate weighed the remaining powder and estimated that she had snorted up 55 milligrams—550 times an average dose, enough to get an entire school tripping on acid. It was a rollercoaster mega-trip that would last 34 hours.

The first 12 hours were hellish. She mostly blacked out and vomited frequently, while being looked after by her roommate. For the next 12 hours after that, CB said she felt “pleasantly high,” mostly sat in a chair, “frothing at the mouth, occasionally vocalizing random words and vomiting frequently,” according to Haden’s account.

When the drug finally wore off another 10 hours later, CB felt normal, and her chronic pain had completely disappeared. For seven years she had been taking morphine every day to treat symptoms of Lyme disease. After her LSD overdose, not only had her pain evaporated, she felt no withdrawal symptoms from the opioids she had been taking.

CB stopped taking morphine for five days, and then her pain did return. She then reduced her dose of opioids and started microdosing LSD (taking about a quarter of a typical dose or 25 micrograms) every three days for a few years before completely stopping the morphine in January 2018, again without withdrawal symptoms.

There is some evidence that psychedelics like LSD can treat pain because they are anti-inflammatory drugs, but Haden was surprised it could help with opioid withdrawal symptoms as well. “I heard somebody say that he thought LSD would be good for withdrawals, but I've never seen any evidence of it,” he said. There is almost no evidence LSD may help with bipolar disorder, let alone “cure” it. Ayelet Waldman, author of A Really Good Day, claims microdosing LSD helped manage her mood disorders. A clinical trial in Switzerland is currently recruiting people to look at LSD to treat manic depression. Otherwise, there’s not much there.

CB’s trip isn’t the most intense LSD overdose recorded or even the first time someone mistook LSD for cocaine. In a 1972 report published in the Western Journal of Medicine, four men and four women each snorted two lines of white powder that was acid, not blow. It’s hard to estimate how much they took, but blood samples ranged from 1,000 to 7,000 micrograms per milliliter. That’s about between 260 and 2100 hits of LSD.

Ten minutes later, all of them ended up in the emergency room. Five were comatose, while the others were “extremely hyperactive with severe visual and auditory hallucinations,” according to the report. Three patients stopped breathing and needed to be put on ventilation machines. Other symptoms included diarrhea, vomiting, bleeding, blood clots and fever (the cocaine, which they had also taken, could have caused the bleeding).

All eight patients survived, and fully recovered less than 12 hours later, most with no memory of being admitted to the hospital. The study authors stated that “no apparent psychological or physical ill effects were noted in a year of follow-up examinations of five patients. Most of the patients continue to use LSD intermittently.”

While there’s never been a recorded death from LSD directly, the authors estimated that a lethal dose of LSD would be around 14,000 micrograms. People do sometimes take too much of a psychedelic and stumble into traffic or out of a window. It’s also possible to die from overdosing on drugs like 25I-NBOMe, which often looks like acid blotter, but can be deadly, which underscores the importance of knowing what drug you are ingesting. Overall, this points to the incredible relative safety of LSD, which is regularly confirmed in clinical trials.

“It's a remarkably safe product. It’s unusual,” Haden said. “Albert Hofmann, [the first scientist to synthesize LSD in 1938], said it was one of the least toxic drugs on the planet and that kind of is consistent with David Nutt’s toxicity data. That’s just another reason why it shouldn’t be criminalized — it’s remarkably non-toxic.”