In a conclusion that won’t please the states that have legalized the recreational use of marijuana, a study found about a third of the psychotic disorders in London are caused by cannabis use.
The study in the Lancet concluded that taking cannabis daily tripled the chances of developing a mental disorder.
“But using forms with high levels of the active ingredient THC made users five times more likely to be affected,” said the Christian Institute, which reported the results.
The study explained, “Between May 1, 2010, and April 1, 2015, we obtained data from 901 patients with first-episode psychosis across 11 sites and 1,237 population controls from those same sites. Daily cannabis use was associated with increased odds of psychotic disorder compared with never users.”
The odds were nearly five times higher “for daily use of high-potency types of cannabis,” the study found.
The incident rates for “psychotic disorder were positively correlated with the prevalence in controls across the 11 sites of use of high-potency cannabis … and daily use,” it said.
The study said: “Differences in frequency of daily cannabis use and in use of high-potency cannabis contributed to the striking variation in the incidence of psychotic disorder across the 11 studied sites. Given the increasing availability of high-potency cannabis, this has important implications for public health.”
The researchers said that in “the context of the well reviewed epidemiological and biological evidence of a causal link between heavy cannabis use and psychotic disorders, our findings have substantial implications for mental health services and public health.”
“Education is needed to inform the public about the mental health hazards of regular use of high-potency cannabis, which is becoming increasingly available worldwide.”
The BBC reported lead researcher Marta Di Fort warned, “If you decide to use high potency cannabis bear in mind there is this potential risk.”
“People experiencing psychosis lose touch with reality, and may hear voices, see things that are not actually there or have delusional, confused thoughts. It is a recognized medical condition and different to getting high on a drug,” the BBC said.
The researchers, from King’s College in London, found that even removing the most potent forms of the drugs would reduce the number of “psychosis” cases.
The Guardian of London reported powerful cannabis, such as skunk, “has levels of the psychoactive substance tetrahydrocannabinol (THC) above 10%.”
A Home Office spokesman said: “No illegal drug can be assumed to be safe as there is no safe way to take them. Drugs can devastate lives, ruin families and damage communities.”
Former Metropolitan Police Chief Bernard Hogan-Howe previously said after the legalization of cannabis in Canada and some states that the U.K. should reconsider its position on the drug.