Long-Term Heavy Cannabis Use Linked to Structural Brain Changes

[David Baxter PhD]

Long-Term Heavy Cannabis Use Linked to Structural Brain Changes
by Caroline Cassels

June 6, 2008 ? Long-term, heavy cannabis use has been linked with structural brain abnormalities, a new study shows.

Investigators at the University of Melbourne, Australia, found the hippocampus and the amygdala tend to be smaller in heavy cannabis users compared with nonusers, with average volume reductions of 12% in the hippocampus and 7.1% in the amygdala. Cannabis use was also associated with subthreshold symptoms of psychotic disorders.

Cannibis use is a controversial topic; the authors note there are many who believe cannabis is relatively harmless and should be legally available. However, the current findings suggest otherwise.

"These findings challenge the widespread perception of cannabis as having limited or no neuroanatomical sequelae. Although modest use may not lead to significant neurotoxic effects, these results suggest that heavy daily use might indeed be toxic to human brain tissue," they write.

It is estimated that 15 million Americans use cannabis in a given month, that 3.4 million are daily users with a duration of 12 months or more, and that every year 2.1 million start using the drug.

Led by Murat Y?cel, PhD, the study is published in the June issue of Archives of General Psychiatry.

Mechanism Unclear
According to the authors, this is the first human study of long-term heavy cannabis use to show marked hippocampal volume reductions. The findings, they add, are consistent with the view that cannabis use increases the risk of psychotic symptoms.

For the study, researchers performed high-resolution structural magnetic resonance imaging (MRI) on 15 men who smoked more than 5 joints daily for more than 10 years. With an average age of 39.8 years and a mean duration of regular use of 19.7 years, the subjects had no history of polydrug abuse or neurologic/mental disorder.

MRI results from these subjects were then compared with those of 16 matched controls who did not use cannabis.

Despite the large magnitude of effect, it is unclear whether volumetric reductions are due to neuronal or glial loss, a change in cell size, or a reduction in synaptic density. The investigators say more research is needed to explain the underlying mechanisms.

The study also showed hippocampal volume in cannabis users was inversely correlated with cumulative exposure to the drug in the left, but not right, hemisphere ? a finding that suggests that "the left hippocampus may be particularly vulnerable to the effects of cannabis exposure and may be more closely related to the emergence of psychotic symptoms."

According to the investigators, "further prospective, longitudinal research is required to determine the degree and mechanisms of long term cannabis-related harm and the time course of neuronal recovery after abstinence."

Source: Arch Gen Psychiatry. 2008;65:694-701. [Abstract]

See also Log In Problems

 

[electric_sheep]

The saddest thing about the chronicle of cannabis use/abuse in this country is the history of sensationalism and hyperbole. Going all the way back to when John Sinclair was thrown in jail for 4 years in the late 60's for having 2 joints on him.

I think the entire country would benefit from a sensible, rational, scientifically based discussion about the POSSIBLE and real dangers of cannabis use... both moderate use and heavy use. Including a discussion about the very real possibility of addiction, even if it isn't a physical addiction, but rather a psychological addiction. The difference between the two may eventually be shown to be transparent anyway. The importance of having a rational discussion cannot be overstated though.

Right now, to be perfectly honest, the illegality of it is simply not even taken seriously by a large majority of the population. This is probably the direct result of a societal reaction and attitude that was disproportionate to the "reality" of cannabis use. I know I smoked it for a year or two when I was a late teenager, and I used to laugh at those "this is your brain on drugs" commercials. There probably are real risks of using cannabis, and so many people simply don't take them seriously because society has simply cried wolf one too many times.

 

[David Baxter PhD]

It seems to me that publicizing the results of research studies like this, instead of publicizing more politics and propaganda on either side of the debate, does in fact constitute the rational discussion you request in your post.

 

[electric_sheep]

It seems to me that publicizing the results of research studies like this, instead of publicizing more politics and propaganda on either side of the debate, does in fact constitute the rational discussion you request in your post.

Absolutely, which is why I welcome it.

I think people in the West have a pretty high degree of faith in science and medicine, so studies like this would be far more effective in swaying public opinion than sensationalism.

Of course, science can only provide us with facts. The policy decisions must balance the risks of addictions and harm with ideas such as personal responsibility and civil liberties (not to mention practical issues like the feasibility and effectiveness of enforcement). The same measuring stick should be applied uniformly too, which begs the question... should we re-evaluate alcohols acceptance in our society? Do studies on the long term effects of heavy alcohol use show it to be of similar harm? Even if they do... should the government control a substance that can be used both safely and destructively? That would include a lot.

 

[David Baxter PhD]

Thanks for the clarification, electric_sheep. I misunderstood your previous post.

 

[timjohnson]

Anybody have any information on psychotic reactions related to cannabis use? I have personally had trouble with it in the past and it's not fun. The doctors were not easy to convince that it was the only thing I had taken in 3 months until they got their toxology reports and everything... One of the psychologists I spoke to a few weeks ago said that there are accruing more findings that some people are "sensitive" to marijuanna or something. I wouldn't doubt that it's the case. On the other hand, some of the marijuanna nowadays has fairly powerful hallucinogenic properties. I know first hand that it's possible to have experiences with it that will keep you up for days and days without sleep and drive you crazy.

I don't want to go too much into that stuff because I know some people take it as a trigger... But having had a psychotic breakdown from it personally I have a lot of anger towards it, and the kinda attitude my friends seemed to have that when you go into the deep water you fend for yourself. They don't tell you that they'll bail if you are in trouble! Then again it's hard to help somebody, or do anything else when you're constantly in a distorted version of the real world. I think the movie "Traffic" kinda shows the attitude I'm talking about, where they just leave their friend in front of the hospital when he's dying. I don't feel honest blaming the people involved, so I blame the drug. I just think it can put people in bad circumstances, and it was like I was constantly skirting disaster, and yet I did it all with a smiling face! I laughed at everything up until it was all over... And now almost a year after some truly horrible events conspired, I am finally starting to remember all of the bad bad things that happened. I somehow had a laugh about being brutalized! And I guess if I had to try to pin down what my addiction was, it was that it covered up all of the things about myself that I didn't want to see. Which I now see is dishonest and undesirable from every perspective. And it seems to me that a lot of people use it to just cover stuff up. And I just think it's at it's core a fashionable, and superficial nothing. And looking back at myself that's the kinda attitude I see then... Then again if somebody said all this to me then I would just shrug it off and tell them they just didn't get it. I sure remember telling my best friend that in the past!

Well anyway, didn't realize I'd blow a gasket responding to this thread! But if anybody has any information about psychotic reactions related to this substance I am fairly interested in it. I guess I want to know more about what happened to me in the past.

 

[ladylore]

I had a similar experience Tim. I have said it on here before but its worth mentioning again - the pot of today is nothing like it was in the 60's. It's stronger and who knows what is mixed in with it. Just because its 'natural' doesn't mean it's safe.

:2cents:

 

[David Baxter PhD]

Apart from the issue of sensitivity to cannabis, one thing many people don't understand is what gets mixed in with weed or hash to cut it or "boost" it. Among the toxins that have been found in street weed are strychnine, PCP, speed, and a variety of household cleansers.

 

[electric_sheep]

Just because its 'natural' doesn't mean it's safe.

I had plenty of friends growing up that were dead heads/hippies, and they used to always extol the virtues of pot and mushrooms based on this idea that they are "natural".

Isn't hemlock natural too? How about the poison from a King Cobra?

The "natural" argument is sort of ridiculous.