"There were no significant associations between lifetime use of any psychedelics, or use of LSD in the past year, and increased rate of any of the mental health outcomes," Pål-Ørjan Johansen and Teri Krebs from the Norwegian University of Science and Technology in Trondheim concluded in their study published in the PLOS One journal on Tuesday.
"Rather, in several cases psychedelic use was associated with a lower rate of mental health problems."
For the study, the researchers analyzed data on the more than 130,000 Americans who took drug use surveys between 2001 and 2004, of which 22,000 had used a psychedelic drug at least once.
"Despite popular perceptions, expert harm assessments have not demonstrated that classical serotonergic psychedelic substances such as LSD, psilocybin, and mescaline are demonstrated to cause chronic mental health problems," Johansen told The Local.
"Everything has some risk: psychedelics can elicit temporary feelings of anxiety and confusion, but accidents leading to serious injury are extremely rare," Krebs added. "Over the past 50 years tens of millions of people have used psychedelics and there just is not much evidence of long-term problems."
She said that their results were consistent with the guidelines of the UN, EU, US, and UK official drug education programs.
Johansen said that earlier studies which demonstrated that psychedelic drugs damaged mental health had been based on a small number of case reports from patients who were already mentally ill.
"Both mental illness and psychedelic use are prevalent in the population, likely leading to many chance associations," he said.
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He pointed out that about three percent of people suffer a psychotic disorder over their lifetimes, while as many as one in six Americans have taken psychedelic drugs.
Moreover, as the use of psychedelics and the onset of mental illness both tended to take place in late adolescence, mistaken causal inferences had often been made.
In an earlier study, published last year, the two neuroscientists demonstrated that a single dose of LSD was an effective treatment for alcoholism.