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INDIVIDUALS WHO USE cannabis every day are three times more likely to suffer from a psychotic disorder than those who don’t use the drug at all, a new study has revealed.
The study, which examines how cannabis use and strength affects the incidence of psychosis, found that the odds of having the disorder among daily users of the drug were 3.2 times higher than among non-users.
It also found that users of high-potency cannabis were approximately 1.6 times more likely to have a psychotic disorder than those who never used the drug.
The study, published today in The Lancet Psychiatry journal, claims to be the first to show the impact of cannabis use on population rates of psychosis, and highlights the potential public health impact of changes to the legal classification of cannabis.
To carry out the study, researchers compared more than 2,000 people between the ages of 18 and 64 at 11 sites in Europe and one in Brazil between 2010 and 2015, in order to understand the risk factors associated with the disorder.
Of these, 901 patients had presented to mental health services following their first episode of psychosis, while a further 1,237 were studied as “healthy matched controls”.
Comparing the two groups, researchers collected information about participants’ history of the use of cannabis and other recreational drugs.
They used published data on levels of delta-6-tetrahydrocannabinol (THC) – the psychoactive compound in cannabis – to evaluate the potency of cannabis used by participants.
They also separated cannabis used by participants into two categories: cannabis classed as high potency, where its THC content was over 10%, and cannabis classified as low potency (under 10%).
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The research found that daily cannabis use was more common among patients who had their first episode of psychosis (266 of 901 participants), compared to the “healthy” control group (84 of 1,237 participants).
Meanwhile, high-potency cannabis usage was more likely among patients who had their first episode of psychosis (334 of 901 participants) than those in the “healthy” control group (240 out of 1,237 participants).
The study also discovered that psychosis was five times more likely among those who used high-potency cannabis on a daily basis, and estimated that one in five new cases of psychosis across the 12 sites in the study were linked to daily cannabis use.
In two sites, Amsterdam and London, high potency cannabis was found to be a strong predictor of psychotic disorders.
In Amsterdam, four in 10 (43.8%) new cases of psychosis were estimated to be linked to daily cannabis use, and five in 10 (50.3%) new cases were linked to high potency use.
Meanwhile, rates of psychosis in London were 21% among daily users, and 30.3% among those who used the drug with high rates of THC.
The researchers suggested that if high potency cannabis was no longer available, the incidence of psychosis in Amsterdam would be expected to halve from 37.9 to 18.8 per 100,000 people per year, while in London, it would fall from 45.7 to 31.9 per 100,000 people per year.
At-risk individuals
Dr Marta Di Forti of King’s College London, the lead author of the study, claimed the findings were consistent with other studies linking high cannabis potency with adverse effects on mental health.
“As the legal status of cannabis changes in many countries and states, and as we consider the medicinal properties of some types of cannabis, it is of vital public health importance that we also consider the potential adverse effects that are associated with daily cannabis use, especially high potency varieties,” she said.
The research follows observational studies which have supported a causal link between cannabis use and psychosis, although none has previously shown that patterns of cannabis use can influence rates of psychosis on a national level.
Commenting on the findings, Dr Suzanne H Gage of the University of Liverpool suggested that the findings indicated that a new approach to treating psychosis among cannabis users was required.
“Given the changing legal status of cannabis across the world, and the associated potential for an increase in use, the next priority is to identify which individuals are at risk from daily potent cannabis use, and to develop educational strategies and interventions to mitigate this,” she said.
People Before Profit TD Gino Kenny suggested that regulating cannabis for recreational use would allow Irish users to consume the drug more carefully.
Kenny’s Cannabis for Medicinal Use Regulation Bill is currently moving through the Dáil, although the government delayed the Bill with a money message last year.
“We need to have a grown-up conversation about this,” he told TheJournal.ie.
“There are forms of unregulated street cannabis that have very high forms of THC, which can be sold by people who are sometimes unscrupulous.
“Regulation would take it out of their hands and allow users to make a choice about the strength of cannabis they use, even if it wouldn’t stop varieties with high levels of THC.”
He added that the findings did not affect his call for the legalisation of cannabis for medicinal use, which contains low levels of THC.
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London and Paris are just as complicit keeping Putin in power. They should freeze these billionaire oligarchs bank accounts and deport them and their faimilies back to Russia. English football needs to get their money from less dubious sources, or every football fan has a hand in keeping navalny in prison
@Clurichaun: absolutely…… But its Convenient to look the other way. The Russians have used nuclear weapon and biological weapon in the UK. But with brexit they will want Russian money. So the decent Russians are on their own.
@Clurichaun: Did you see the beating the French police were giving protesters yesterday? People on the ground were being birched with big sticks, it’s difficult to be critical when police in Paris & Catalonia are doing exactly the same.
@Joe Thorpe: hardly the same thing. The people of Russia want freedom from generations of corruption and political assassinations. The geniuses in France won’t follow basic public health advice while thousands die in hospitals
@Joe Thorpe: Well that’s yellow vest nut jobs. We have then here too G.O.D I’d buy the French police a beer if what you said is true.
If this happened in the USA the condemnation and screams would be heard from across the Atlantic. I always find it amazing how the Russians and Chinese generally get a free pass from The Western Media. Very strange.
@Crispy Brown: nail on the head mate, why no putin hatred here in Ireland or condemnation, irish people are so manipulated in their thoughts by the mainstream media its hilarious, no putin bashers no?, most Irish people probably don’t even know who he is, just thousands of people on here for months saying how much better off the world is now without Donald trump, yer a joke,
@Crispy Brown: day do not speakit de English
@Hugo Bugo: got one thing right BETTER OFF WITHOUT THE TWITTERING TWIT
One cold-war era trained Heavy, and his favourite acquired sidemen, will be incapable of halting the march of a nation towards true democracy and freedom.
And Navalny is the Leader to see this through, given his past independence from outdated and corrupt Sovereign Governance machine ruling that eleven time-zoned Country for over three decades.
English Electorate, please observe closely and learn for fear of slippage into similar undemocratic ways by your political masters.
@Rory J Leonard: maybe you should check Navalny’s track record before you start putting any hopes in him. Another ‘pro democracy’ merchant with questionable values to say the least. I am not a supporter of Putin either
@alan: track record? Post. But not from Pro kremlin government controlled media
Like him or hate him Russia needs a strong leader like Putin. If Russia was to fall into the hands of anarchists there be dire consequences for the rest of the world.
@Michael Maher: or into US stooges like Yeltsin. A man who brought the country to its knees.
@Eugene Norman: Correct the man was a drunk.
@Eugene Norman: The blame for Putin lies squarely on US shoulders and the West in general. They put Yeltsin in power and enabled oligarchs by privatising public companies so they could do easier business deals. They went back on their promise to Gorbachev not to bring any more countries into Nato in return for a peaceful German reunification. Gorbachev knew exactly how Nato expansion into satellite countries would be used to fuel paranoia in Russia and leverage political opportunities.They even helped write the Russian constitution to suit their own ends. They have destroyed Ukraine through interfering in its economic and political affairs and afforded Putin the opportunity to annex Crimea without breaking sweat. The West has no moral high ground when it comes to Putin. They are reaping what they sowed.
@Michael Maher: It has fallen into the hands of a KGB agent (Putin) and a want to be dictator (Trump)
Apparently no one believed them when they said a Russian oligarch owned the palace with a no fly zone and 2km avoidance zone on the black sea.
Before you jump to conclusions make sure you look into navalny, a far right nationalist should not be supported blindly because you have been told putin is bad doesn’t mean anti-putin is better
Bring back the red flag
have your say