Pubdate: Sat, 16 Apr 2016
Source: Guardian, The (UK)
Copyright: 2016 Guardian News and Media Limited
Author: Ian Sample, Science editor


UN Meeting to Discuss Growing Drugs Problem

Up to Quarter of Psychosis Cases Could Be Prevented

The risks of heavy cannabis use 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 the first special session on the global drugs 
problem 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, 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."

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 estimates suggest that deterring heavy use 
could prevent 8 to 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 presence of the high-inducing substance THC 
(delta-9 tetrahydrocannabinol) has increased from 4% to 12% in 
cannabis seized by the Drug Enforcement Administration. The number of 
users rose from 14.5 million to 22.2 million in the seven years to 2014.

But young people's perceptions of the risks have fallen, a 
consequence perhaps of the public discussion over legalisation and 
fewer restrictions for medicinal use, 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.

In the UK, cannabis is the most popular illegal drug, and according 
to Public Health England data more young people enter treatment 
centres for help with cannabis than any other drug, alcohol included. 
The number of under-18s in treatment for cannabis use rose from 9,000 
in 2006 to 13,400 in 2015. The drug now accounts for three-quarters 
of young people receiving help in specialist drugs centres. The most 
common age group is 15- to 16-year-olds.

The reasons for the upward trend are unclear. As hard drugs fall in 
popularity, clinical services may simply pull in more cannabis users. 
But the rise in young people in treatment may be linked to the skunk 
that has taken over the market.

Skunk and other strong forms of cannabis now dominate the market in 
many countries. From 1999 to 2008, the cannabis market in England 
transformed from 15% to 81% skunk. In 2008, skunk confiscated on the 
street contained on average 15% THC, three times the level found in 
resin seized that year. The Home Office has not recorded cannabis 
potency since. "There is no doubt that high-potency cannabis, such as 
skunk, causes more problems than traditional cannabis, or hash," 
Murray said. "This is the case for dependence, but especially for 
psychosis." 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.

"People are not going to develop psychosis from having a couple of 
joints at a party. We're talking about people who smoke every day and 
throughout the day."

The evidence that cannabis can cause psychosis is not 100% 
conclusive. It is still possible that people who are prone to 
psychosis are simply more likely to use the drug.

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.

Public health campaigns can easily fail. To prevent a single case of 
schizophrenia, several thousand heavy cannabis smokers would probably 
have to quit.

As with any campaign, credibility is everything. "There is an issue 
of getting a message through to those who are vulnerable without 
causing alarm, being overly sensationalist and thus being ignored," 
said Dr Wendy Swift of the National Drug and Alcohol Research Centre 
at the University of New South Wales.

A UK government spokesman 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."


What are the risks?

Can people overdose on cannabis?

Not easily. Scientists estimate that the lethal dose of the drug is 
somewhere in the range of 15 to 70g. That is far beyond the daily 
consumption of even the most enthusiastic user.

What are the short-term effects?

Beyond the high that attracts about 180 million people a year 
worldwide are side effects that range from anxiety and paranoia to 
problems with attention, memory and coordination. The acute mental 
impairment explains why stoned drivers are twice as likely to crash 
their cars as unimpaired drivers.

Can people become dependent on cannabis?

Yes. Studies suggest that one in 10 regular users become dependent on 
the drug, or one in six of those who start in their mid-teens. The 
number of people seeking professional help to quit or control their 
cannabis habit has risen in Europe, the US and Australia.

What are the long-term effects?

Mental health problems are one of the greatest concerns. Nearly 30 
years ago, a study of Swedish conscripts found that those who 
reported using cannabis more than 50 times by the age of 18 were 
three times more likely than others to have schizophrenia at 45. 
Other studies support the findings, but do not prove beyond doubt 
that cannabis causes mental health problems.

Is high-potency cannabis more harmful than weaker strains?

Last year, scientists at King's College London studied a population 
of south Londoners and found that those who smoked skunk every day 
had five times the normal risk of psychosis. A later study from KCL 
found that those who smoked skunk daily had subtle changes that could 
impair communication between the two sides of the brain.

How big is the risk to regular users?

Daily users have a 2% chance of developing schizophrenia in their 
lives, about double that of the general population. Work is now under 
way to find out who are the most vulnerable people.
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MAP posted-by: Jay Bergstrom