Current Events . . . Community
42 Members
Avatar universal

Cannabis Use in Teens Linked to Irreparable Drop in IQ

Cannabis Use in Teens Linked to Irreparable Drop in IQ
Fran Lowry
Apr 26, 2013

ORLANDO, Florida — Cannabis users who start smoking the drug as adolescents show an irreparable decline in IQ, with more persistent use linked to a greater decline, new research shows. On the other hand, adult-onset cannabis use is not linked to a decline in IQ.

"Our results suggest that adolescents are particularly vulnerable to develop cognitive impairment from cannabis and that the drug, far from being harmless, as many teens and even adults are coming to believe, can have severe neurotoxic effects on the adolescent brain," lead investigator Madeline H. Meier, PhD, from Duke University, Durham, North Carolina, told Medscape Medical News.

The study was presented here at the 14th International Congress on Schizophrenia Research (ICOSR).

Prospective Study

Studies on the neurocognitive effects of cannabis are particularly timely, inasmuch as 18 US states have legalized cannabis. The drug is also being used for medical indications, such as pain relief, which further creates the idea in people's minds that it is harmless, Dr. Meier said.
Dr. Madeline Meier

"Case-control studies show that light to heavy cannabis use can cause enduring neuropsychological problems, but they are retrospective and there are no tests of premorbid functioning," she said.

In the current study, Dr. Meier and colleagues used data from the Dunedin Longitudinal Study, which was conducted in Dunedin, New Zealand. This prospective study included a birth cohort of 1037 individuals born in 1972 and 1973, who were followed from birth and were seen every 2 years to age 38.

"This study has collected prospective life histories on its participants and had 95% retention," Dr. Meier said.

Participants' cannabis use was ascertained in interviews at ages 18, 21, 26, 32, and 38 years. IQ testing was done at age 8, 11, and 13 years, before the start of cannabis use, and again at age 38, after a pattern of persistent cannabis use had developed. One third of the cohort had never used cannabis.

After controlling for alcohol or drug dependence, socioeconomic status, and years of education, the researchers found that persistent cannabis use was associated with IQ decline when it was begun during the teenage years but not when begun in the adult years, after the age of 18.

Between the ages of 8 and 38 years, individuals who began using cannabis in adolescence and continued to use it for years thereafter lost an average of 8 IQ points. In contrast, IQ among individuals who never used cannabis actually rose slightly, Dr. Meier said.

Cessation of cannabis did not restore IQ among teen-onset cannabis users, she added.

"Anybody working with adolescents in particular has to be aware that adolescents are more at risk for cognitive functioning problems," Dr. Meier said.

"Also, when you are working with an adult patient in therapy who has been using cannabis since adolescence, be aware that they may not be functioning at their highest cognitive level, and so therapy should take that into account," she said.

Additionally, pediatricians and others adults who come in contact with children regularly should be aware of the danger, Dr. Meier added.

"I think teachers, parents, health educators, and pediatricians should all be trying to get the message out to adolescents that drugs, especially cannabis, are not harmless. I think that data in the US especially show that adolescents seem to be getting the message that cannabis is harmless, and trying to counteract that erroneous view is really important."

Particularly Potent Pot?

"As psychiatrists, we are all interested in psychosis, but we have to remember that psychosis only affects about 2% of the population, but we all have IQ," commented Robin MacGregor Murray, MD, DSc, professor of psychiatric research at the Institute of Psychiatry, Kings College, London, United Kingdom.
Dr. Robin Murray

"If these results are borne out in other studies, and if what we have heard from Madeleine is true, because you can't immediately presume that one study is predictive of all studies, but if the effect of cannabis on IQ is replicated, then that's a really big deal," Dr. Murray told Medscape Medical News.

He added that the cannabis in New Zealand is very strong and has been so for years, with a THC content of approximately 9%. "That might account for these results," he said.

Dr. Murray also noted that other studies have shown that it takes a long time for the effects of cannabis to "wash out," and he would also like to see research on how long it takes adults to regain their memory and other cognitive functions once they stop using the drug.

Dr. Meier and Dr. Murray report no relevant financial relationships.

14th International Congress on Schizophrenia Research (ICOSR). Abstract S267. Presented April 25, 2013.

16 Responses
1310633 tn?1430227691
Right at the end, it sort of addresses my question... how long does it take for the effects to go away?

If you smoke between the age of say 14 & 18, then stop, how long will it take for you to undumba$$?

I can't say I'm surprised about the link (between lower IQ and weed-use). Looks like the stereotypical "pothead", "stoner" portrayed on TV, has some validity, scientifically.  
Avatar universal
Interesting.  I agree with el... look at the stereotypical pothead.  Normally not the brightest lamp in the furniture store.
Avatar universal
I think you both are overlooking the main point which is the deleterious effects of adolescent marijuana use. A chronic abuser of any substance is not likely to be at the top of his/her game...like drunks and coke heads and speed freaks and heroin addicts and chain smokers. There are exceptions but, as a rule, the stereotypical abusers aren't the the best performers.
Having said that, I do know occasional pot smokers who are extremely successful. A friend of mine in college smoked pot several times a week and is now a self made billionaire. I also smoked in college and law school and I've done alright. A few months ago 4 other friends of mine went to dinner together in a limousine and brought with them 4 bottles of wine worth approximately $1400 a bottle. Obviously they are all quite successful financially with good jobs and they all have good family lives too. They smoked a joint together on the drive to dinner and from their account they had a great evening.
The study I posted is not conclusive in my opinion but it does suggest that adolescent marijuana abuse may be fraught with danger. I would very much like to see some follow up studies on this issue.
Avatar universal
If you smoke between the age of say 14 & 18, then stop, how long will it take for you to undumba$$?
You crack me up el!!!

I wonder about the other variables in the life of a teenager who smokes pot regularly.
The lifestyle of an adolescent pothead would not be conducive to intellectual growth considering the other needs of a growing mind for nutrition, structure, enrichment and stimulating activities and so on.
1530342 tn?1405020090
Umm, I dunno abowt dis won..LOL
Avatar universal
I think I got what the article was about.  I was referencing the few teenagers I know that smoke up on a regular basis.  First of all, the kids I am talking about weren't too bright to begin with.  (They live in households where there is no real parental guidance and no support systems.)  And since these kids have been smoking (2 years that I know of) both are doing worse in school, neither is motivated to do anything.  It's tragic and you can almost hear them getting dumber.

It is a sad, sad, thing.

I know adults who smoke regularly and have gone on to make something of themselves, but they also had a little something upstairs to start off with.  That teemed with a bit of gumption/motivation has put a few of them in very good positions financially.  
Avatar universal
Brice I agree 100%. By no means was I implying that smoking pot had anything to do with my friends' success. It just didn't seem to get in the way.
206807 tn?1331939784
I smoked Pot on a regular basis when I was a Teen and I don’t think it affected me at all long term (I’m sure some of you object to that). I think Pot is a lot stronger now than it used to be. It use to relax me but I tried it a couple of years ago and it didn’t relax me at all. Like Mike, I know several, successful people that occasionally smoke it but I also know several people my age that smoke it on a regular basis and not one of them will ever be accused of being the “Sharpest Knife in the Drawer.”
Avatar universal
I wonder if the three college friends of the terrorist all smoked for a long time? That might explain why they seem so stupid to be in college.
163305 tn?1333672171
I'm such a damn skeptic~ I want to see what the test questions to determine IQ are.

Truthfully, anything can be done in excess. Look at the obesity that is hard to ignore and yet, no food, no life.

I'd still rather the kids smoke a little weed than get drunk though we older folks always want the kids to stay  sober little virginal darlings.
However that's not real life.
Avatar universal
we older folks always want the kids to stay  sober little virginal darlings.
However that's not real life.

Isnt that the plain truth of it! LOL
Avatar universal
Marijuana Not Medicine, Addiction Experts Say

Kathleen Louden
Apr 29, 2013

CHICAGO — Illinois should not legalize cannabis, and physicians should not write recommendations for patients to use marijuana for medical purposes, because it is a dangerous, addictive drug and is not approved by the US Food and Drug Administration (FDA), a group of addiction medicine physicians said during a press conference here.

"Marijuana should not be approved outside of FDA-approved channels," said Stuart Gitlow, MD, MPH, president of the American Society of Addiction Medicine (ASAM), which sponsored the news conference here during the society's 44th Annual Medical-Scientific Conference.

Dr. Gitlow reiterated ASAM's position against "medical marijuana" days after the Illinois House of Representatives passed a bill that would legalize medicinal cannabis in the state if approved by the Illinois Senate.

To be medication, marijuana would need proper consideration by the FDA as to its risks and benefits, dosage, and timing of the drug, he said.

"There is no such thing as medical marijuana," Dr. Gitlow stated.

Marijuana "Unstable and Unpredictable"

Another speaker, Andrea Barthwell, MD, an addiction medicine specialist and a coauthor of ASAM's white paper on the legalization of marijuana, called cannabis "unstable and unpredictable" and said that the drug should be subject to the same standards that apply to other medications.
Dr. Stuart Gitlow

She told Medscape Medical News that the Illinois bill, known as the Compassionate Use of Medical Cannabis Pilot Program Act, does not require the same standards.

"Under the Illinois bill, you have to be certified to obtain physician-recommended marijuana only once," Dr. Barthwell, a former deputy director for demand reduction in the White House Office of National Drug Control Policy, said in an interview. "If you get a prescription for a narcotic painkiller, when you finish the prescription, you have to go back to the physician."

Narcotic painkillers are schedule II controlled substances. Marijuana remains a schedule I controlled substance in the United States, meaning the Drug Enforcement Administration (DEA) finds that it has no currently accepted medical use, lacks accepted safety for use under medical supervision, and has a high potential for abuse.

Marijuana is the most common illicit drug causing dependence in the United States, according to a 2011 survey from the Substance Abuse and Mental Health Services Administration.

The Illinois Compassionate Use of Medical Cannabis bill proposes implementation of a 4-year pilot program aimed at protecting "patients with debilitating medical conditions, as well as their physicians and providers, from arrest and prosecution" for using marijuana for medical reasons, such as to control pain or nausea.
Dr. Andrea Barthwell

The bill allows use of cannabis in any form, including smoking, which Dr. Barthwell and other speakers said is unsafe because it exposes the smoker to carcinogens.

If the bill is enacted, Illinois would become the 20th state, along with the District of Columbia, to allow the medical use of marijuana.

In another argument against the proposed legislation, John Peterson, MD, president of the Illinois Society of Addiction Medicine, said during the press conference, "For every disease and disorder for which marijuana has been recommended, there is a better, FDA-approved medication."

Such medications, he said, include dronabinol (Marinol, AbbVie), an oral synthetic cannabinoid approved to treat nausea and vomiting associated with cancer chemotherapy and to treat appetite loss and wasting in people with AIDS.

However, some people with vomiting reportedly have problems swallowing a pill. In addition, advocates of legalization of medical marijuana say some patients do not get any relief from available medications or derive greater benefit from marijuana than from other medicines.

When asked by Medscape Medical News at the press conference to comment on this suggestion, Dr. Gitlow said, "There are probably very few patients for whom marijuana is the only drug that makes them feel better. Is it worth the risk to our society to give one person an intoxicant to help them feel better — while not getting better — and put our entire society at risk by making that intoxicant available to all?"

Opposing Views

That argument was disputed by Christopher Fichtner, MD, a public health psychiatrist in Riverside, California, and a former Illinois state mental health director, who is a member of the Marijuana Policy Project, which lobbies to legalize marijuana for seriously ill patients.

When asked by Medscape Medical News to comment by telephone, Dr. Fichtner, who was not involved with the ASAM press conference, said, "The idea that marijuana is very dangerous is pure fiction. Just like anything, there can be abuse. It's up to the individual to use it responsibly."

He also disagreed with another argument raised during the press conference, that the dose of marijuana cannot be regulated. In California, which legalized medical cannabis in 1996, marijuana products undergo laboratory testing for potency and purity, and the products carry a label that states the amount of tetrahydrocannabinol, the active ingredient, according to Dr. Fichtner, who said he does not write medical marijuana recommendations.

"The physicians I know who make recommendations view marijuana as safer than opioids and a lot of our over-the-counter medications, such as anti-inflammatories," he said. "Plus, a lot of people who are taking marijuana as their primary relief for pain are greatly reducing their use of opioid narcotics."

Illinois' Compassionate Use of Medical Cannabis Pilot Program Act lists approximately 30 debilitating medical conditions, including cancer, AIDS/HIV infection, cachexia, and spinal cord diseases, for which patients would be eligible for the program. The bill would allow a person with one of these physician-diagnosed conditions to possess up to 2.5 ounces of usable cannabis during a 14-day period.

David Ostrow, MD, PhD, president of the American Academy of Cannabinoid Medicine and a former psychiatrist specializing in addiction medicine in Illinois, said that he considers the number of eligible conditions listed "very restrictive."

Dr. Ostrow, who was not involved in the press conference, told Medscape Medical News that the proposed allowable amount of cannabis is reasonable.

"Some people need a lot of marijuana to ease their symptoms," he said.

Dr. Ostrow added that physicians who write marijuana recommendations should follow best medical practices. He believes they also should receive training regarding safe and effective use of marijuana to treat medical conditions, stating that such training is available from the American Academy of Cannabinoid Medicine.

During the ASAM press conference, former DEA administrator Peter Bensinger said that 2.5 ounces of marijuana is "almost a dealer quantity, equivalent to 183 joints." He said that if this high amount is allowed, it will lead to patients giving away or selling some of the drug.

Dr. Gitlow reports that he is a consultant to Orexo AB, a pharmaceutical company headquartered in Uppsala, Sweden. None of the other sources report any relevant financial relationships. Dr. Gitlow is executive director of the Annenberg Physician Training Program in Addictive Disease, which has multiple program sites. Dr. Barthwell is director of Two Dreams Outer Banks Drug and Alcohol Treatment Center in North Carolina.

American Society of Addiction Medicine (ASAM) 44th Annual Medical-Scientific Conference. Press Conference. Presented April 25, 2013.

You must join this user group in order to participate in this discussion.
Didn't find the answer you were looking for?
Ask a question
Popular Resources
A list of national and international resources and hotlines to help connect you to needed health and medical services.
Here’s how your baby’s growing in your body each week.
These common ADD/ADHD myths could already be hurting your child
This article will tell you more about strength training at home, giving you some options that require little to no equipment.
In You Can Prevent a Stroke, Dr. Joshua Yamamoto and Dr. Kristin Thomas help us understand what we can do to prevent a stroke.
Smoking substitute may not provide such a healthy swap, after all.