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Teens who smoked marijuana at least four times a week and used marijuana throughout their life saw their IQ drop an average of 8 points, according to a new study.
By Tia Ghose, LiveScience
Teens who smoke marijuana see their IQs drop as adults, and deficits persist even after quitting, according to a new study.
"The findings are consistent with speculation that cannabis use in adolescence, when the brain is undergoing critical development, may have neurotoxic effects," study researcher Madeline Meier of Duke University said in a statement.
The study followed 1,037 New Zealand children for 25 years. Subjects took IQ tests at age 13, before any of them had smoked marijuana, and again at age 38. Throughout the study, participants also answered several surveys about their drug use.
Roughly 5 percent of the participants started using marijuana as teenagers. Those who smoked marijuana at least four times a week and used marijuana throughout their life saw their IQ drop an average of 8 points, the equivalent of going from an A to a B student. The drop was not explained by other drug use, years of education, schizophrenia or using marijuana in the day before the test.
People who eventually quit smoking pot still had lower IQs than they did at the start of the study.
Interestingly, people who picked up the habit as adults had no IQ drop, suggesting that marijuana may not be as harmful to the mature brain.
The findings are the first to associate intelligence declines with marijuana use. Past work linked low IQ and marijuana, but couldn't rule out the possibility that people who choose to smoke pot are inherently less smart than abstainers.
It's not clear why pot is bad for teen brains.
One possibility is that teenagers are more vulnerable to marijuana's effects on brain chemistry, said Susan Tapert, a neuropsychologist at the University of California, San Diego, who was not involved in the study.
During adolescence, neural connections are pruned in the hippocampus and the prefrontal cortex, critical regions for learning, memory and planning, Tapert said.
Those regions may also soak up the active ingredient in marijuana."A lot of the areas that are still developing during adolescent years happen to be the areas with high cannabis receptor density," Tapert told LiveScience.
But those who consistently smoke marijuana may simply make less intellectually stimulating choices at critical points in life.
"What people tend to do when they're under the influence is different than they would otherwise," Tapert said.
For instance, pot users may be less inclined to attend classes or do other activities that give the brain a workout. Getting off track early on can also limit future opportunities and thereby reduce IQ, she said.
Related: 10 Ways to Keep Your Mind Sharp
"Teens need to view cannabis as not an entirely benign compound, but as something that can impair your judgment and might not be great for your brain," Tapert said.
The study is detailed Aug. 27 in the journal Proceedings of the National Academy of Sciences.
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This just in being born leads to death. The assumptions some people jump to today are funny. The question I would ask is did they look into all factors that lead to reduced IQ? Even aging can lead to reduced IQ.
nice try..pot has nothing to do with stupid
This study must be biased, because I was a heavy daily user of pot all through high school, and still managed to keep a 3.8 GPA in all the college prep classes (calculus, physics, chem, etc). Not only did I use daily, I would be high for most tests and while doing homework. My college CPA was the same while studing to be an Electronic Engineer. I admit I never had my IQ tested in adolescence, but it's been consistent since college through middle age at 135.
Wow: Wonder what it would be if you'd stayed off the mind altering drugs?
138
If memory serves me correct. Back when I qualified to join Mensa, there were 2 scales for IQ. One I believe was the Cattell scale? Can't remember the other....
Educate yourself on marijuana before you come to the conclusion that it is bad for you. Yes like anything it is bad for minors because their brain is still developing but for adults it is good for so many diseases!! Diabetes, cancer, Tourette's, your eyes, blood pressure, heart disease, any sleeping disorder as it helps regulate your sleep, eating disorders, bipolar disorders, ADHD... and i can go on all day long... The risk of a marijuana user that smokes it getting cancer is only slightly higher than someone who doesn't smoke anything and way below the percentage that cigarettes cause!! Does anyone think that there might be reasons that ppl lie to the world about marijuana effects!! um let me see for one if made legal it may cripple the tobacco industries which invest in the government!! and many other reasons!! Alcohol is dangerous, it kills your liver and impairs your brain functions, and has slim to no medical uses!!
It could be however that these 38 year old have just simply forgotten the basic skills that are on the IQ test and have focused their intelligence on their career path as many of us do as we get older and do the same repetitious things day in and day out!! I mean come on we have all seen "Are You Smarter Than A 5th Grader?" right. It is not the marijuana that makes a bad name for itself, its the dumb people that choose not to look at all aspects of the situation and then come to an educated decision about it!! research all sides and be knowledgeable about it before you knock it!! I have used marijuana for 10 years and I am 25!! I graduated High School with honors and about to graduate college with a 3.8 GPA I have a full time 8-5 office job m-f take care of my smart beautiful child by myself and live very well off all by myself.... You would be surprised of the intelligent people that you may have contact with everyday smoke weed on a regular basis!!
they figure its about time they better find something negative about marijuana compared to alcohol which ruins and kills thousands a people a year legally or cigarettes which kills much more.
Don't like what you're hearing? Just change the subject. LOL.
Nearly 600,000 people killed yearly from alcohol and tobacco. With many of them sucking up my tax dollars for heath care they have no hope of paying for.
Not one confirmed death from cannabis usage though.
I am not saying that cannabis usage wont make you complacent in your life, or prevent you from moving up a corporate ladder, but this is just another fear mongering campaign.
If it weren't for stoners, who would work at our convenience stores?
I hate how everyone says "Nobody has ever died from marijuana." How the hell do you know? If a person dies from lung cancer due to a life of smoking cigs, they don't list the cause of death as "Cigarettes".
okay, find 1 documented case of stoner dies from lung cancer. ive been smoking my whole, i probably work harder then 99% of the people on these forums, and i know im in better shape then you and 99% of these people on the planet. i never get sick, i trail run 4 to 5 miles at altitudes above 8000 feet up to 10,000, during winter i ski 5 days a week and never get tired. im up at 6am and dont sit down until 8 or 9pm. i have had my lungs checked and the dr said i have a greater lung capacity then most of his patients over his 20 years as a Dr. of course he doesn't recommend that i smoke but he cant see any negative side affect it has caused me.
The death certificate would list drug overdose if it was from Cannabis since it's listed as an illegal narcotic.
maybe if they found the person dead in the street. if they got lung cancer from cannabis they would suffer for however before they died and it would say died of lung cancer from smoking.
Pot does not have cancer causing agents
Ryan:
Because if there was a documented case where someone died directly as a result of smoking pot the Prohibitionist crowd would be shoving it down our throats.
As of yet, they have failed to find that one documented case.
Ha ha all the pot heads! Whoa man its for everyone! Well apparently not!
I know alot of people that can handle booze and others can't..what the hell are you thinking or not that its fine for everyone?
Oh I liked the moron that said "legalize it and this will reduce the use from minors"...study proves that IQ's do decrease over time! Idiot!
....yep...and these same teens grow up to become democrats.
When I was in high school I could find pot pretty easy but had to really work (and pay!) to get someone to purchase alcohol or cigarettes for me. Not sure if that has changed in the past 20 years, but it just goes to shows that legalization and regulation work.
I am alleady stupid, can't find my bong. Where did i place it?
Maybe you ex boyfriend was stupid from the get go. Maybe you are stupid to have made him your boy friend.
Read what you wrote. Better yet, get someone NOT stoned to read it to you. Then call her stupid again.
No such thing as a free lunch....No such thing as a free high. And the higher and/or more frequent the high, the more you pay in the long run.
good thing pot safer than alcohol,a ceeper free ride.
ameridian:
Pay more in the long run how?
so, I should tell my kids they cant' smoke pot until they are 20?
richlee:
No. 21.
I guess that is why the teenagers that use pot are aptly called pot heads. And yet a great many people think pot is an alright drug. Any drug that affects your brain is not an all right drug.
guenavere:
Pot is an "alright" drug compared to alcohol, tobacco, caffeine, and definitely compared to the other illegal hard drugs.
If you had read the article (which either you didn't, or did but are twisting the facts to support your prohibitionist stance) people who smoke after their brains are fully developed don't have a reduction in IQ. It's only young developing people that should abstain from all drugs until they are adults.
Mind altering drugs have been around for thousands of years and for you to come along and try and change that you will fail miserably.
But, according to your last statement we should outlaw anything that affects your brain. That would include many legal substances, too, no?
Outlaw things that affect the brain....hmmmm...sugar, caffeine, chocolate, etc. THAT list would pretty endless.....
is this story a politically corrct joke!!?? the high school i went to,the pot heads were the smart kids. they may not of had a lot of friends,but they were very smart.
lies from the murder machine, so if you know a pot smoker and he make far more money than you that makes you what? dumber than dumb.other study say other wise. i know drunks that have been drinking from early teen yrs. and man they can't make it out a wet paper bag or go to work stay married on and on.
Hey Bud,
Spicoli begs to differ!
If you haven't tried it, don't knock it.... Now where did i put the pipe?
Yep, My Dr. just tried to give me opiates. Ha Ha Ha Ha and that stuff must be safe right?? Well he got to keep it.
It has nothing to do with the pot. Kids are getting more and more stupid on thier own. The are lazy and have no respect for anything or anyone. I live in the country and last halloween we witnessed a 10 year old boy threatening to mug old people as they walked around and nobody did anything about it, and if he was high he would have been much calmer.
Lazy too - if potheads would drop that Twinkie and get off mom's sofa for a few minutes. Grow their own then dopers would not have to depend on dealers or worry about the law. Medical pot could be grown in the attic, basement or closet but because users are lazy or have a IQ problem - growing is almost impossible.
oldandtried - Actually growing is very easy, emphasis on very. I grew my own for 2 years, and I know absolutely nothing about growing. It's not too difficult to stick a plant in dirt, give it some water, and let Mother Nature do the rest. Drop the Twinkie and get off mom's couch? I'm 56 years old, and smoked for over 20 years. I've always had my own home, paid taxes, and raised 2 great kids. Ppl like you w/ this attitude of smokers all being indolent and good-for-nothings really need to get an education. Smokers comprise a thick cross-section of people and occupations. You are ignorant and need to do some research. If you're really old, maybe you've missed your chance...
Did any of you morons actually make it thru the article? Their assertion is that pot has caused these people to be lazy and not attend school or other brain enhancing activities,,,I say bs, this entire article is ridiculous.
one study and yes it was bia from start
Whoa - Dude! No Way, Man! I'm 29 years old delivering pizzas for Papa Johns, living in my mom's basement, & smokin doobies - that's way smart, man!
Way to perpetuate a stereotype.
Bobs ur uncle, do some research and try educating yourself. Reality is a wonderful thing.
Odd. I have smoked marijuana. I was an A student when I was young. I am an A student now. Usually the people who complain the most about marijuana take a list of pharmaceutical drugs. Of course the medical profession will complain, addicting people to pharmaceutical drugs is how doctors make their money. All the doctor has to do is fraudulently document the medical records to cover their tracks. Take a look around your area and see how many doctor and/or dentist offices have caught fire. If the whole building isn't destroyed, the rear of the building where the records are kept is destroyed. That has happened with quite a few offices in my neighborhood. Believe me it is not a coincidence. The medical profession is that corrupt.