Pubdate: Sun, 29 Nov 2015
Source: Forbes Magazine (US)
Copyright: 2015 Forbes Inc.
Contact:  http://www.forbes.com/forbes/current/
Details: http://www.mapinc.org/media/769
Author: Alice G. Walton

DOES HIGH-POTENCY MARIJUANA DO MORE DAMAGE TO THE BRAIN?

There's been a long and heated debate about whether marijuana actually 
triggers long-term changes in a person, both neurologically and 
psychologically. Some research has found that pot is linked to psychotic 
symptoms, and it's certainly been linked to schizophrenia across 
multiple studies. However, it's a bit of a chicken-or-egg problem, since 
it can be difficult to tell which is the pre-existing "condition," the 
pot smoking or the psychological/psychotic symptoms. Now, a new study 
from King's College London finds that smoking skunk, a high-potency 
variety of pot, is linked to changes in the white matter connections 
between the two hemispheres of the brain. And this seems to be true 
whether a smoker experiences psychosis or not.

Skunk has higher levels of the psychoactive compound 
Delta-9-tetrahydrocannabinol (THC) than "regular" pot, and has become 
much more prevalent in recent years, as people seek out more potent 
versions of the drug.

The researchers scanned the brains of 56 people who had sought treatment 
for a first episode of psychosis, and 43 healthy controls. The team 
looked at the density in the brain's corpus callosum, the vast network 
of white matter tracks that extend from neurons in one hemisphere to 
cells in the other. Damage to the white matter connections means less 
efficient communication between brain cells, which itself can be linked 
to cognitive problems.

It turned out that there some significant links between how often a 
person smoked and how likely they were to have changes in their white 
matter: People who smoked skunk more often had a greater likelihood of 
damage their white matter than people who smoked less frequently or who 
smoked lower-potency version. And using skunk was linked to white matter 
damage regardless of whether or not psychotic symptoms were reported.

"We found that frequent use of high potency cannabis significantly 
affects the structure of white matter fibres in the brain, whether you 
have psychosis or not," said author Paola Dazzan. "This reflects a 
sliding scale where the more cannabis you smoke and the higher the 
potency, the worse the damage will be."
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Of course, cause and effect cannot be illustrated with a study like 
this. By definition, the only type of connection here is a correlation, 
since the researchers did not assign people to smoke pot or abstain 
during a set period of time. But the "dose-dependent" relationship 
between pot and white matter changes in the brain could suggest that the 
one causes the other, though more research is need to understand how the 
relationship originates. It could theoretically be the other way round: 
that people who naturally had white matter damage to begin with are more 
likely to smoke pot as a way to self-medicate, and the worse the damage, 
the more active the pot smoking.

This is certainly not the first study to suggest a link between pot 
smoking and brain changes. Earlier research has also found changes in 
other areas of the brain, like the gray matter of the hippocampus, the 
seat of learning and memory. And several have linked marijuana to 
psychotic symptoms and to schizophrenia, but again, it's unclear which 
way the relationships work, and they may very likely work in both 
directions.

What is clear is that high-potency marijuana is more readily available 
than it was. A study earlier this year, analyzing recreational and 
medical marijuana, showed that the THC content in pot can reach up to 
almost 30%, whereas a few decades ago it was just about 10%. Meanwhile, 
the other active compound cannabidiol (CBD), which is thought to have 
therapeutic value, has fallen steadily. There doesn't seem to be much 
regulation in any kind of marijuana these days, and it's unclear how and 
whether this will change moving forward. While researchers are still 
figuring out what kind of brain effects are associated with pot, if 
you're a user, try to use in moderation, and definitely stay away from 
the high-potency stuff. And even more, stay far away from synthetic pot, 
as it's been linked to the most severe symptoms, and even to death. 
Hopefully science will have some more concrete answers to all of these 
questions in the not-too-distant future.
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MAP posted-by: Matt