Pubdate: Tue, 19 Jan 2016
Source: Denver Post (CO)
Copyright: 2016 The Associated Press
Contact:  http://www.denverpost.com/
Details: http://www.mapinc.org/media/122
Author: Malcolm Ritter, The Associated Press

STUDY CHALLENGES POT'S LINK TO TEEN INTELLIGENCE DROP

New York (AP) - A new analysis is challenging the idea that smoking 
marijuana during adolescence can lead to declines in intelligence.

Instead, the new study says, pot smoking might be merely a symptom of 
something else that's really responsible for a brainpower effect seen 
in some previous research.

It's not clear what that other factor is, said Joshua Isen, an author 
of the analysis. But an adolescent at risk for smoking pot "is 
probably going to show this IQ drop regardless of whether he or she 
is actually smoking marijuana," said Isen, a lecturer in psychology 
at Loyola Marymount University in Los Angeles.

The study was released Monday by the Proceedings of the National 
Academy of Sciences.

Researchers examined data that had been collected for two big U. S. 
studies of twins. They focused on 3,066 participants who were given a 
battery of intelligence tests at ages 9 to 12 - before any of them 
had used marijuana- and again at ages 17 to 20.

They tracked changes in the test scores and studied whether those 
trajectories were worse for marijuana users than for nonusers. Most 
tests revealed no difference between the two groups, but users did 
fare more poorly than abstainers in tests of vocabulary and general knowledge.

If smoking pot harmed test scores, the researchers reasoned, people 
who had smoked more pot should show poorer trends than those who had 
smoked less. But that's not what the data revealed.

The study also looked at 290 pairs of twins in which one had used 
marijuana and the other had not. Again, the pot users did not fare worse.

So, the researchers concluded, pot smoking itself does not appear 
responsible for declines in test scores. Isen noted that the work 
says nothing about other potential harmful consequences of smoking 
marijuana in adolescence.
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MAP posted-by: Jay Bergstrom