Pubdate: Tue, 28 Aug 2012
Source: New Zealand Herald (New Zealand)
Copyright: 2012 New Zealand Herald
Contact:  http://www.nzherald.co.nz/
Details: http://www.mapinc.org/media/300
Author: Nicholas Jones

TEEN DOPE USE CAUSES LONGLASTING HARM TO IQ

Big NZ-Based Study Sounds Alarm Over Danger of Smoking Drugs Early

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."
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