Can cannabis use cause psychosis?
Yes, but so can overuse of caffeine, nicotine, alcohol, stimulants and hallucinogens. Psychosis is a symptom: a temporary disorientation that resembles a waking dream, with odd, imagined sights and sounds, often accompanied by paranoia or an ominous sensation. The vast majority of people who have this kind of psychotic experience do not go on to develop a persistent condition such as schizophrenia, which is characterized by episodes of psychosis that recur for years, as well as cognitive problems and social withdrawal.
Can heavy use cause schizophrenia or other syndromes?
That is the big question, and so far the evidence is not strong enough to answer one way or the other. Even top scientists who
specialize in marijuana research are divided, drawing opposite conclusions from the same data.
"I've been doing this research for 25 years, and it's polarizing even among academics," said Margaret Haney, a professor of neurobiology at Columbia University Medical Center. "This is what the marijuana field is like."