WebMD.com

The idea of marijuana causing a psychotic breakdown sounds like something out of the camp film classic "Reefer Madness," but many experts argue it's not that far-fetched.

As legalization of recreational marijuana spreads across the United States, more people are showing up in ERs with psychotic symptoms after consuming too much pot, said Dr. Itai Danovitch, chairman of psychiatry and behavioral neurosciences at Cedars-Sinai in Los Angeles.

"If somebody gets too high, they use more than intended, they can have psychotic symptoms. That typically resolves as the drug wears off," Danovitch said. "After it's worn off, there's no subsequent psychosis. That's just a direct effect of over-intoxication."

But some unlucky souls with a family history of mental illness might wind up with a full-fledged psychotic disorder that will require extended treatment, Danovitch noted.

"That risk is concentrated among a minority of people who have an existing vulnerability to develop a psychotic disorder, a family history of psychosis," Danovitch said. "There are environmental factors that influence whether somebody develops schizophrenia who has a risk. It appears cannabis probably is one of those factors."

Vaping a potent form of THC -- the intoxicating ingredient in pot -- prompted a psychotic episode last year in 24-year-old Madison McIntosh of Scottsdale, Ariz., according to USA Today.

McIntosh appeared at the driving range where he worked on his day off, wandering around and talking babble for 12 hours straight. His family rushed him to a hospital, where he told his father that he was seeing double rainbows. Doctors diagnosed him with cannabis use disorder and unspecified psychosis.

McIntosh remembers feeling "out of it, delusional," at the driving range, where he thought people were following him. "I was pretty scared," he told USA Today of the March incident. "I didn't know where I was at."

Disagreement over pot-psychosis link

Despite anecdotes like these, skeptics argue that the science on a potential link between pot and psychosis remains far from solid.

"It would appear to be premature, at best, and sensational, at worst, to opine that a strong causal relationship exists between cannabis exposure and psychiatric disorders, given the lack of consensus among experts in the field and the fact that rates of psychosis and mental illness have largely remained static over the decades while at the same time rates of cannabis use have fluctuated dramatically," said Paul Armentano. He is deputy director of NORML, a nonprofit calling for the reform of marijuana laws.