Around one in 10 cases of psychosis, a condition where a sufferer has trouble determining what is real and what is fake, has been linked to daily use of strong strains of cannabis.
Research published Tuesday, in The Lancet Psychiatry Journal, connects high levels of THC, the cannabis ingredient that gets you high, to the likelihood of first episodes of psychosis, with daily users becoming up to five times more likely to experience the psychotic disorder.
The study focuses on ”skunk” cannabis, which contains 14 percent THC, and makes up 94 percent of the drug strain being sold in London, where nearly a third of the psychotic disorder diagnoses have been linked to its use.
An estimated 30 percent of cases in highly affected areas, like South London and Amsterdam, could have been avoided if high-THC level cannabis was not as easily available.
Scientists estimate that the removal of high-THC cannabis would decrease the psychosis incidence rate in London from 46 percent to 32 percent, per 100,000 people yearly.
Researchers studied five countries in the EU–the Netherlands, UK, France, Spain, and Italy– and found that amongst those suffering from the psychotic episodes, 30 percent used cannabis, with THC levels over 10 percent, daily.
Psychosis, or experiencing a psychotic episode, consists of delusions and hallucinations, from hearing voices to seeing things that aren’t there, and does not relate to the side effects of getting high.
Medical cannabis is legal in most countries in the EU; however, personal, recreational cannabis use is only legal in the Netherlands, Spain, and the Czech Republic.
Many European countries are contemplating legalising recreational cannabis use, though the impact on health is still unknown.
Similar links to heavy cannabis use have been found in those suffering from depression and paranoia.