Use of Cannabis in Adolescence Linked to Lower IQ

[holy king]

if i pass by. i'm certainly not planning on getting lost looking for you.

 

[Borachio]

How can you be lost if you can see the entire universe? Where are you? Why, everywhere.

 

[holy king]

it's called psychosis.

 

[GoodGame]

I'm pretty sure JAMA run ran an article about marijuana use negatively affecting memory in some capacity, in the 1990s. I'll have to google scholar it sometime.

http://jama.jamanetwork.com/article.aspx?articleid=396766

Spoiler :

Objective. —To assess whether frequent marijuana use is associated with residual neuropsychological effects.

Design. —Single-blind comparison of regular users vs infrequent users of marijuana.

Participants. —Two samples of college undergraduates: 65 heavy users, who had smoked marijuana a median of 29 days in the past 30 days (range, 22 to 30 days) and who also displayed cannabinoids in their urine, and 64 light users, who had smoked a median of 1 day in the last 30 days (range, 0 to 9 days) and who displayed no urinary cannabinoids.

Intervention. —Subjects arrived at 2 PM on day 1 of their study visit, then remained at our center overnight under supervision. Neuropsychological tests were administered to all subjects starting at 9 AM on day 2. Thus, all subjects were abstinent from marijuana and other drugs for a minimum of 19 hours before testing.

Main Outcome Measures. —Subjects received a battery of standard neuropsychological tests to assess general intellectual functioning, abstraction ability, sustained attention, verbal fluency, and ability to learn and recall new verbal and visuospatial information.

Results. —Heavy users displayed significantly greater impairment than light users on attentional/executive functions, as evidenced particularly by greater perseverations on card sorting and reduced learning of word lists. These differences remained after controlling for potential confounding variables, such as estimated levels of premorbid cognitive functioning, and for use of alcohol and other substances in the two groups.

Conclusions. —Heavy marijuana use is associated with residual neuropsychological effects even after a day of supervised abstinence from the drug. However, the question remains open as to whether this impairment is due to a residue of drug in the brain, a withdrawal effect from the drug, or a frank neurotoxic effect of the drug.(JAMA. 1996;275:521-527)

http://jama.jamanetwork.com/article.aspx?articleid=194703

Spoiler :

< Previous ArticleNext Article >
Original Contribution | March 6, 2002
Cognitive Functioning of Long-term Heavy Cannabis Users Seeking Treatment FREE
Nadia Solowij, PhD; Robert S. Stephens, PhD; Roger A. Roffman, DSW; Thomas Babor, PhD, MPH; Ronald Kadden, PhD; Michael Miller, PhD; Kenneth Christiansen, PsyD; Bonnie McRee, MPH; Janice Vendetti, MPH;
JAMA. 2002;287(9):1123-1131.
Text Size: A A A
Article
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ABSTRACT
ABSTRACT | METHODS | RESULTS | COMMENT | REFERENCES

Context Cognitive impairments are associated with long-term cannabis use, but the parameters of use that contribute to impairments and the nature and endurance of cognitive dysfunction remain uncertain.

Objective To examine the effects of duration of cannabis use on specific areas of cognitive functioning among users seeking treatment for cannabis dependence.

Design, Setting, and Participants Multisite retrospective cross-sectional neuropsychological study conducted in the United States (Seattle, Wash; Farmington, Conn; and Miami, Fla) between 1997 and 2000 among 102 near-daily cannabis users (51 long-term users: mean, 23.9 years of use; 51 shorter-term users: mean, 10.2 years of use) compared with 33 nonuser controls.

Main Outcome Measures Measures from 9 standard neuropsychological tests that assessed attention, memory, and executive functioning, and were administered prior to entry to a treatment program and following a median 17-hour abstinence.

Results Long-term cannabis users performed significantly less well than shorter-term users and controls on tests of memory and attention. On the Rey Auditory Verbal Learning Test, long-term users recalled significantly fewer words than either shorter-term users (P = .001) or controls (P = .005); there was no difference between shorter-term users and controls. Long-term users showed impaired learning (P = .007), retention (P = .003), and retrieval (P = .002) compared with controls. Both user groups performed poorly on a time estimation task (P<.001 vs controls). Performance measures often correlated significantly with the duration of cannabis use, being worse with increasing years of use, but were unrelated to withdrawal symptoms and persisted after controlling for recent cannabis use and other drug use.

Conclusions These results confirm that long-term heavy cannabis users show impairments in memory and attention that endure beyond the period of intoxication and worsen with increasing years of regular cannabis use.

 

[Terxpahseyton]

In other news, drinking heavily or smoking crack on a regular basis for years when you're growing up lowers your IQ too.

Even smoking tobacco excessively does to. It dries up oxygen in your brain.

 

[CaptainF]

Correlation doesn't equal causation. Duh.

Take all the anecdotes you want, but cannabis effects everyone differently. Some children in MMJ states in the U.S. are managing to overcome serious chronic medical issues with medical cannabis.

I really think that cannabis doesn't change your personality all that much. Sure, many people who smoke pot in their teen years go on to be burnouts. In all likelihood, they would have been burnouts anyway. At the same time, there are many people who achieve wonderful success later in life. I know a few individuals who started smoking in their teen or even pre-teen years who now make six-figure incomes in demanding fields.

If anything, it adds one more argument to why cannabis should be legal: to more easily keep it away from children.

 

[civver_764]

Is it bad that this study just makes me want to smoke weed even more?

 

[SS-18 ICBM]

Correlation doesn't equal causation. Duh.

The authors agree that they haven't proved causation.

First, although we were able to rule out a set of
plausible alternative explanations for the association between
persistent cannabis use and neuropsychological functioning, such
as premorbid neuropsychological deficit and hard-drug and alcohol
dependence among persistent cannabis users, our data
cannot definitively attest to whether this association is causal.

They do, however, suggest possible mechanisms.

One hypothesis
is that cannabis use in adolescence causes brain changes
that result in neuropsychological impairment. Several lines of
evidence support this possibility (24&#8211;31, 33, 34). First, puberty is
a period of critical brain development, characterized by neuronal
maturation and rearrangement processes (e.g., myelination,
synaptic pruning, dendritic plasticity) and the maturation of
neurotransmitter systems (e.g., the endogenous cannabinoid
system), making the pubertal brain vulnerable to toxic insult
(33). Second, cannabis administration in animals is associated
with structural and functional brain differences, particularly in
hippocampal regions, with structural differences dependent on
age and duration of exposure to cannabinoids (33). Third,
studies of human adolescents have shown structural and functional
brain differences associated with cannabis use (26, 29, 35).
Alternatively, persistent cannabis users may experience greater
neuropsychological decline relative to nonusers because they
receive less education.

The numbers indicate other papers that support their points. I can furnish the citations if you so desire.

but cannabis effects everyone differently.

So does pretty much every drug. However, what is important is the effect for the majority of people. And their data suggests that there is a decline in IQ, P=0.0007.

 

[Terxpahseyton]

Is it bad that this study just makes me want to smoke weed even more?

Yep (mind you, I like some weed myself). Seems to relate all too well to your statement in the confessions thread.

 

[Borachio]

Wow! Cannabis affects the brain. Breaking news here, eh?

How plastic is the brain, btw? Is it possible to increase one's IQ? So is it possible by hard work and diligence to overcome the negative effects of cannabis, after ceasing consumption?

Just too many variables here to come up with any workable hypothesis.

 

[Hygro]

Or people who smoked hella weed as teenagers just didn't do the things that the non smokers do to keep their brain as sharp. The study comes across like its some kind of chemical brain damage when all it is might just be a lack of brain exercise.

 

[Borachio]

IQ tests are so suspect. Which is why I practice them all the time.

 

[SS-18 ICBM]

Or people who smoked hella weed as teenagers just didn't do the things that the non smokers do to keep their brain as sharp. The study comes across like its some kind of chemical brain damage when all it is might just be a lack of brain exercise.

Except they controlled for that.

How plastic is the brain, btw? Is it possible to increase one's IQ? So is it possible by hard work and diligence to overcome the negative effects of cannabis, after ceasing consumption?

It will be difficult, especially if you're older, but still possible.

Just too many variables here to come up with any workable hypothesis.

What are "sample size" and "controls"?

 

[Borachio]

Yes, I know the study quoted used those. I was thinking of my own, rather hazy, hypothesis.

 

[Borachio]

it's called psychosis.

Only if you find it scary, though. (And indeed I would)

 

[rugbyLEAGUEfan]

I don't see where the study accounts for quantity? Smoking the odd joint on a weekend is a totally different ball game to sitting around every day punching 30 cones.

 

[Borachio]

Two samples of college undergraduates: 65 heavy users, who had smoked marijuana a median of 29 days in the past 30 days (range, 22 to 30 days) and who also displayed cannabinoids in their urine, and 64 light users, who had smoked a median of 1 day in the last 30 days (range, 0 to 9 days) and who displayed no urinary cannabinoids.

Well, I suppose you're right. In a way.

 

[azzaman333]

Doesn't surprise me. Even if the brain is still developingat 18, if that is our age of adulthood, cannabis should be allowed at 18. If brains aren't developed enough, change the age of adulthood.

Did you just say you'd be happy for cannabis to be legalized for adults?!

 

[civver_764]

He's always thought that.

 

[GhostWriter16]

Is it bad that this study just makes me want to smoke weed even more?

Yes

Did you just say you'd be happy for cannabis to be legalized for adults?!

He's always thought that.

For at least a good while...

Although my political concern is mostly for ending the "War on Drugs" moreso than drug laws in themselves, a ban on canabis makes no sense to me, for adults.

Teenagers aren't adults under the law and so it makes sense to me that they shouldn't be allowed to use drugs. I know this will just make civver764 do it even more but a law being in place might stop teenagers from making poor decisions while they are not yet of the age of adulthood. I don't support anyone, even teenagers, going to jail for using any drug though.