Cannabis: scientists call for action amid mental health concerns

The Guardian 15 April 2016
Family First Comment: A UK government spokesperson said its position on cannabis was clear. “We must prevent drug use in our communities and help people who are dependent to recover, while ensuring our drugs laws are enforced. There is clear scientific and medical evidence that cannabis is a harmful drug which can damage people’s mental and physical health, and harms communities.”   Nicely summed up.

The risks of heavy cannabis for mental health are serious enough to warrant global public health campaigns, according to international drugs experts who said young people were particularly vulnerable.

The warning from scientists in the UK, US, Europe and Australia reflects a growing consensus that frequent use of the drug can increase the risk of psychosis in vulnerable people, and comes as the UN prepares to convene a special session on the global drugs problem for the first time since 1998. The meeting in New York next week aims to unify countries in their efforts to tackle issues around illicit drug use.

While the vast majority of people who smoke cannabis will not develop psychotic disorders, those who do can have their lives ruined. Psychosis is defined by hallucinations, delusions and irrational behaviour, and while most patients recover from the episodes, some go on to develop schizophrenia. The risk is higher among patients who continue with heavy cannabis use.

Public health warnings over cannabis have been extremely limited because the drug is illegal in most countries, and there are uncertainties over whether it really contributes to mental illness. But many researchers now believe the evidence for harm is strong enough to issue clear warnings.

“It’s not sensible to wait for absolute proof that cannabis is a component cause of psychosis,” said Sir Robin Murray, professor of psychiatric research at King’s College London. “There’s already ample evidence to warrant public education around the risks of heavy use of cannabis, particularly the high-potency varieties. For many reasons, we should have public warnings.marijuana - primary drug use graph

”The researchers are keen not to exaggerate the risks. In the language of the business, cannabis alone is neither necessary nor sufficient to cause psychosis. But the drug inflicts a clear burden on the vulnerable. Estimates suggest that deterring heavy use of cannabis could prevent 8-24% of psychosis cases handled by treatment centres, depending on the area. In London alone, where the most common form of cannabis is high-potency skunk, avoiding heavy use could avert many hundreds of cases of psychosis every year.

In the US, cannabis is becoming stronger and more popular. Over the past 20 years, the strength of cannabis seized by the Drug Enforcement Administration has increased from 4%-12% THC. Meanwhile, the number of users rose from 14.5 million to 22.2 million in the seven years to 2014.

Coinciding with the upwards trend, young people’s perceptions of the risks of cannabis have fallen, a consequence perhaps of the public discussion over legalisation and fewer restrictions for medicinal uses, according to the US government’s National Institute on Drug Abuse (Nida).

“It is important to educate the public about this now,” said Nora Volkow, director of Nida. “Kids who start using drugs in their teen years may never know their full potential. This is also true in relation to the risk for psychosis. The risk is significantly higher for people who begin using marijuana during adolescence. And unfortunately at this point, most people don’t know their genetic risk for psychosis or addiction.”

….In Australia, a 2013 study found nearly half of the cannabis confiscated on the streets contained more than 15% THC. Prof Wayne Hall, director of the Centre for Youth Substance Abuse Research at the University of Queensland, said that while most people can use cannabis without putting themselves at risk of psychosis, there is still a need for public education.

….In the 1960s, cannabis in the Netherlands had less than 3% THC, but today high potency strains average 20%. Jim van Os, professor of psychiatry at Maastricht University medical centre, said public health messages are now justified. He believes people should be deterred from using cannabis before the age of 18, warned off the stronger forms, and urged not to use cannabis alone or to cope with life’s problems.

… A government spokesperson said its position on cannabis was clear. “We must prevent drug use in our communities and help people who are dependent to recover, while ensuring our drugs laws are enforced. There is clear scientific and medical evidence that cannabis is a harmful drug which can damage people’s mental and physical health, and harms communities.”
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