Teenage pot smoking may lower IQ – for life

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poledriver

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NZ - Lasting IQ harm from teen dope use

NZ - Lasting IQ harm from teen dope use

The persistent use of cannabis before age 18 has been linked to lasting harm to intelligence, according to a large study.

Analysis of more than 1000 New Zealanders found those who took up cannabis in adolescence and used it for years afterwards experienced an average decline in IQ of eight points when measured at age 13 and 38.

People who did not begin using cannabis until they were adults, with fully formed brains, did not show the same declines.

Experts here and abroad say the findings are significant and could offer some explanation for the "teenage stoner" stereotype.

Lead researcher Madeline Meier of Duke University in Durham, North Carolina, said quitting cannabis later in life did not appear to reverse the loss of intelligence.

Higher IQ correlated with higher education and income and better health, she said.

"Somebody who loses eight IQ points as an adolescent may be disadvantaged compared to their same-age peers for years to come."

The study, to be published in the Proceedings of the National Academy of Sciences, examined individuals in the Dunedin Cohort study, which has followed 1037 people born in 1972-73 in Dunedin from birth.


About 5 per cent of the study group were considered cannabis-dependent, or used the drug more than once a week before age 18.

At age 38, all of the study participants were given a range of psychological tests to assess memory, processing speed, reasoning and visual processing. People who smoked cannabis persistently as teens scored significantly worse on most tests.

The decline in IQ among teenage users could not be explained by alcohol, other drug use or having less education, the team of international researchers found.

Dr Meier said a drop of eight IQ points was significant.

NZ and international experts have said the research provides valuable insight into the harm that could be caused by cannabis.

"Clearly we must focus energy on reducing the prevalence of cannabis use in adolescence," said Dr Simon Adamson, of Otago University's National Addiction Centre.

Ross Bell, head of the NZ Drug Foundation, said a clear picture had emerged that drugs such as cannabis and alcohol were particularly damaging for adolescents.

"The worrying thing in New Zealand is that young New Zealanders have pretty easy access to alcohol and cannabis and substances like butane."

Simply banning drugs such as cannabis and then thinking that was the problem solved would not work, Mr Bell said. "What we're lacking in New Zealand is support for widespread, high-quality, well-constructed prevention messages targeted at younger people."

New Zealanders are among the highest users of illegal drugs in the world, and top the list for cannabis use, according to a United Nations study released in June.

Robin Murray, professor of psychiatric research at King's College London, said the study could offer some explanation for the "teenage stoner" stereotype.

"It is of course part of folklore among young people that some heavy users of cannabis - my daughter calls them stoners - seem to gradually lose their abilities and end up achieving much less than one would have anticipated."

http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10829929
 
ZOSIA BIELSKI
The Globe and Mail
Published Monday, Aug. 27 2012, 6:18 PM EDT

Chronic use of the chronic before age of 18 can cause “lasting harm to a person’s intelligence, attention and memory” – and quitting pot later in life doesn’t reverse the damage, says daunting new research out of New Zealand.

The study, which followed 1,037 Kiwis for nearly 40 years, found that adolescents who smoked marijuana persistently for years showed declines of eight IQ points when their scores were tabulated at age 13 and then at 38. Teens who got stoned regularly all scored significantly worse than their sober counterparts on tests measuring memory, reasoning and processing speed, with family and friends of users corroborating the findings anecdotally.

“Marijuana is not harmless, particularly for adolescents,” lead researcher Madeline Meier, a post-doctoral researcher at Duke University, said in a release. “Somebody who loses eight IQ points as an adolescent may be disadvantaged compared to their same-age peers for years to come.”

Adolescent tokers are particularly vulnerable to lasting mental deficits because their brains are still developing, the researchers explained. Subjects who didn’t hit the bong until they were adults “with fully-formed brains” did not exhibit these drastic mental declines.

(Approximately five per cent of the respondents were deemed “marijuana-dependent,” that is, lighting up more than once a week before turning 18. The researchers controlled for other drug and alcohol use and disparities in education.)

What isn’t clear from this study is what quantity of weed causes damage, and what age (if any) might be safe for regular use.

Marijuana use is up among American teens, who are now more likely to smoke pot than tobacco, according to a 2011 University of Michigan study.

That study found one in every 15 high-school seniors getting high on a daily or near daily basis, the most substantive rates seen since 1981.

cont at
http://www.theglobeandmail.com/life...smoking-may-lower-iq-for-life/article4503763/
 
Teenage Marijuana Use May Hurt Future IQ

Reported by Drs. Tiffany Chao and Shari Barnett

Teenagers lighting joints may end up less bright, according to new research released Monday.
In a study of more than 1,000 adolescents in New Zealand, those who began habitually smoking marijuana before age 18 showed an eight-point drop in IQ between the ages of 13 and 38, a considerable decline.
The average IQ is 100 points. A drop of eight points represents a fall from the 50th percentile to the 29th percentile in terms of intelligence.

The research, published in the Proceedings of the National Academy of Sciences, charted the IQ changes in participants over two decades.

Researchers tested the IQs of all of the study subjects at age 13 before any habitual marijuana use. Researchers then split the study into five “waves” during which time they assessed cannabis use — ages 18, 21, 26, 32, and 38. They again tested IQ at age 38. The authors also controlled for alcohol use, other drug use and education level.

The eight-point drop in IQ was found in subjects who started smoking in adolescence and persisted in “habitual smoking” — that is, using cannabis at least four days per week — in three or more of the five study waves.

People who started smoking in adolescence but used marijuana less persistently still had a hit to their IQ’s, but it was less pronounced than the group that used it early and persistently.

In contrast, those who never used marijuana at all gained nearly one IQ point on average.

Madeline Meier, lead researcher and a post-doctoral associate at Duke University, said that persistent use of marijuana in adolescence appeared to blunt intelligence, attention and memory. More persistent marijuana use was associated with greater cognitive decline.

“Collectively, these findings are consistent with speculation that cannabis use in adolescence, when the brain is undergoing critical development, may have neurotoxic effects,” Meier writes in the study.

Of particular worry is the permanence of these effects among people who began smoking marijuana in adolescence. Even after these subjects stopped using marijuana for a year, its adverse effects persisted and some neurological deficits remained. People who did not engage in marijuana smoking until after adolescence showed no adverse effects on intelligence.

Experts in child development said the reasons adolescents may be more susceptible to the harmful effects of marijuana may have to do with a substance called myelin. Myelin can be thought of as a kind of insulation for nerve cells in the brain that also helps speed brain signals along — and in adolescent brains, the protective coating it forms is not yet complete.

“Frontal lobe myelination is not fully completed until age 25 years or so, and the pre-myelinated brain is more susceptible to damage from neurotoxins,” says Dr. Richard Wahl, director of adolescent Medicine at the University of Arizona. “Cannabis, most likely, is a neurotoxin in high and continuous doses.”

The study appears to lend credence to “stoner” stereotypes in popular media. However, no previous studies can provide data for this phenomenon, since establishing whether a drop in IQ has actually occurred requires that a baseline IQ be obtained before a person ever started using marijuana. This study did just that.

“[The findings] provide evidence for the actual — rather than ideological and legal — basis for concerns regarding cannabis use,” said Dessa Bergen-Cico, a assistant professor of public health, food studies and nutrition at Syracuse University. “These findings reinforce recommendations on the importance of primary prevention, evidence based drug education and policy efforts targeting not only adolescents, but elementary age children before they start.”
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from
http://abcnews.go.com/blogs/health/2012/08/27/teenage-marijuana-use-may-hurt-future-iq/
 
I do not trust studies. Especially in the U.S. during an election year.

and Obama, if you happen to be reading this, you sold us down the river with medical m.j. Now there are going to be a flurry of studies showing marijuana in a bad light? That's convenient.

Romney is a Mormon so enough said about him.

I'm so glad I have a little crop. I wish it was bigger since the government in the U.S. is getting more conservative each day.

I wish I could move to Canada.
 
Just wanted to point out that nobody can tell you exactly what IQ scores measure.
They are claimed to measure intelligence, but the people who make these claims cannot define intelligence.
They certainly measure something, but what it is is not clear.
It certainly is culturally-based, and based in mainstream Western/U.S./North American culture specifically.
Therefore, if weed smokers get lower scores on IQ tests, it may be because they have diverged from the mainstream culture in various ways, and it may have little to do with "intelligence".
 
For years, regular marijuana users have dismissed cautionary warnings that the habit killed brain cells, believing it was some kind of urban myth. Well, now scientists have produced evidence to back up the myth: a study of more than 1,000 people in New Zealand who were followed over two decades found that those who started habitually smoking marijuana before age 18 eventually showed an 8-point drop in IQ.
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from
http://atlantablackstar.com/2012/08/27/study-smoking-weed-as-teen-reduces-adult-iq/
 
What does this spell for those of us that started consuming heavily at the age of 18? : P My concern is not great as whatever intelligence I have left, were it actually affected in the first place, is more than enough for even the loftiest ambitions.
 
arohydro said:
What does this spell for those of us that started consuming heavily at the age of 18? : P My concern is not great as whatever intelligence I have left, were it actually affected in the first place, is more than enough for even the loftiest ambitions.
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I like your confidence :)
But no one has shown that intelligence is affected in any way.
If you believe this study, then IQ scores are affected. Very different thing.
 
ugly said:
Who paid for this study?
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Some 14 year old with more pot than sense!

slimvictor said:
Just wanted to point out that nobody can tell you exactly what IQ scores measure.
They are claimed to measure intelligence, but the people who make these claims cannot define intelligence.
They certainly measure something, but what it is is not clear.
It certainly is culturally-based, and based in mainstream Western/U.S./North American culture specifically.
Therefore, if weed smokers get lower scores on IQ tests, it may be because they have diverged from the mainstream culture in various ways, and it may have little to do with "intelligence".
Click to expand...

I remember seeing a documentary on TV years ago about a guy, Cyril Burt, who promoted the IQ test. Apparently, after he died, it was discovered that he fiddled his scientific results for years. There is also an interesting book on IQ.

I believe this is the abstract to the paper in question...
http://www.pnas.org/content/early/2012/08/22/1206820109.abstract
 
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Young cannabis smokers run risk of lower IQ, report claims

Young people who smoke cannabis run the risk of a significant and irreversible reduction in their IQ, research suggests.

The findings come from a study of around 1,000 people in New Zealand.

http://www.bbc.co.uk/news/health-19372456


I think NZ is probably the wrong place to do any kind of study on IQ's :)

Only kidding, I know it's not fair to joke at the expense of our cross Tasman cousins but hey ITS SO EASY lol.

Seriously though, I wish they would do a similar study of the IQ's of people who watch main stream TV through their teenage and young adult years compared to people who don't, I think the results would be astounding.
 
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Bugger, just seen this is already posted in an earlier thread today, Mods please merge it, thanks.
 
Daily Mail - Cannabis is not an innocent drug, teenagers addicted..IQ...brain damage

Cannabis is not an innocent drug, teenagers addicted to it risk damaging their IQ and causing significant brain damage

By Dr Robert Lefever

PUBLISHED: 11:36, 28 August 2012

A magistrate, Yvonne Davies, when sentencing a cannabis grower to community service, urged him to stay away from the drug – after revealing that addiction to cannabis had killed her brother. She spoke about the ‘living hell’ her family had been through. She said, 'If I can stop one family going through what I went through it will be worth it.' Her brother killed himself after becoming a cannabis addict and developing schizophrenia and depression.

Mrs Davies said: ‘He was a very caring and clever person but he had this addiction. ‘At first he would just smoke it at weekends and the family knew about it but we weren’t happy at all. ‘We tried to discuss it with him on a few occasions but he would just brush off our concerns saying that it wasn’t dangerous. ‘But we noticed a change when he started smoking it more than just at weekends.’ He began using the drug on a daily basis. Eventually he lost his job after his employers became aware of his addiction. Mrs Davies said that her brother could not cope with unemployment and so he smoked more cannabis, eventually developing depression.

She said: ‘We noticed a definite change in his personality as he would get angry and very anxious. He was trying to hide it from us but we all knew what was going on and were hoping that he would stop.’ One night, after a row with his parents, he stormed out with the family dog – which returned on its own, soaking wet, several hours later. After ten days, his body was found in a canal.
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The scientific evidence continues to mount. Cannabis is not the innocent weed that some people say it is. Cannabis is a nasty dangerous drug that is addictive in some people. It can cause significant damage to brain function, particularly in the young.

This is the message that needs to be emphasised by social workers, teachers, doctors, politicians and magistrates as well as by parents.
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http://www.dailymail.co.uk/debate/a...ging-IQ-causing-significant-brain-damage.html
 
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