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Cannabis and Teen IQ: get the factsIf you follow me on Instagram or Twitter or Facebook, you might know I was at the Mason County KY town hall on medical Cannabis hosted by KY4MM.org. Mason County is the first county in KY to stand up for patient’s rights — bravo!

During the discussion following the presentation, a doctor spoke her mind about Cannabis and teen IQ. She said Cannabis has a negative long-term effect on teens; my research says otherwise. I asked her to share her evidence and she sent me 18 studies.

If you are interested in seeing those studies and my comments, they are at the bottom of this post. Meanwhile, here’s my response to her:

Dear Dr. CA,

Thank you for sending these studies. While interesting, none of them are conclusive or significant. They are all opinions, full of “mays”, “mights” and “possibly”s. Most start off with a hypothesis to prove. This may be acceptable for a study concluding that more research might be called for (which some of these do), but it’s not science and certainly draws no reliable conclusions.

While repetition is key to establishing reputable data, repeating the same thing over and over again does not make it true. It just makes people believe it’s true. Repetition is only scientifically valid when the exact same results are found conclusively. That is not the case here.

The glaring problem with all of these studies is the veritable mountain of uncontrolled variables, including:

  • lifestyle choices such as food, sugar, sleep, fitness;
  • no accounting for the health of an individual’s major bodily systems: gut, hormonal, adrenal, cardiovascular, thyroid;
  • no discussion of other stress reduction tools a young person might be using;
  • the fact that IQ tests in and of themselves have been called into question (more on that below);
  • no discussion of the quality of education or teachers, both critical factors in determining why a young person would quit school or have difficulty learning.

If these factors were part of the studies, they were apparently considered too insignificant to highlight as causative. I consider them too critical to overlook.

I’ve been in the fitness and alternative health field since 1982. Everyone I know in my field finds the years of anecdotal evidence far more compelling than the average study.

Plus, since most natural substances are not studied*, anecdotal evidence offers the only education and evidence on how these are best used for healing, whether herbs (including Cannabis), homeopathy, essential oils, supplements and/or lifestyle factors.

*These healing modalities are not studied because there’s no money in it.

Cannabis has been used safely, both medicinally and socially, for thousands of years. No one has died from Cannabis use in 5,000 years of recorded history. THIS is significant.

Medical Cannabis has been legal in CA for over 20 years with NO deaths or serious injuries. California kids must not be noticeably dumber because no one is complaining and the government has not taken steps to limit it. In fact, it’s on the ballot for full legalization! THIS is significant.

Medical Cannabis is legal in 25 states and legal socially in 3 others with many more on the way. If it were truly making our teens dumber, wouldn’t somebody have noticed by now and wouldn’t there be a HUGE movement to keep it away from teens? THIS is significant.

Are the legislators, parents and patients in legal states all blind to these studies? Of course not. They have come to the same conclusions I have: pot makes you muddled while you are under the influence and for a few hours afterward, but it is no more addictive than caffeine and has zero long-term negative effects. THIS is significant.

The notion that there is any relationship at all between Cannabis and teen IQ doesn’t hold water, either scientifically or anecdotally.

Education is the way to free ourselves from intense indoctrination and lies by both government officials under the influence of lobbyist money (far more dangerous than pot), and the medical/pharmaceutical industries that have a large, very expensive dog in the fight.

If you are interested in knowing more about medical Cannabis, here are some good resources.

KY4MM’s PowerPoint presentation

This was shown at yesterday’s town hall: http://www.ky4mm.org/wp-content/uploads/2015/06/KY4MM-Library-Presentation.pptx (There are clickable links to research in the PP slides.)

Neuroscientist Dr. Gregory Gerdeman

Discussing the science behind his support: https://www.youtube.com/watch?v=gfB-aIn56G8

Dr. Sanjay Gupta’s Weed documentaries

#1: https://www.youtube.com/watch?v=-SZzgfyXhJI
#2: https://www.youtube.com/watch?v=evBTqPGFhds

Re. IQ tests

IQ tests are one of the many uncontrolled variables. IQ scores can differ for the same person on different IQ tests, so a person does not always belong to the same IQ score range each time tested. IQ tests are generally reliable enough that most people aged 10+ have similar IQs throughout life.

Still, some individuals score very differently when taking the same test at different times or when taking more than one kind of IQ test at the same age.

Many children in the famous longitudinal Genetic Studies of Genius begun in 1921 by Lewis Terman showed declines in IQ as they grew up. Terman recruited school pupils based on referrals from teachers, and gave them his Stanford–Binet IQ test. Children with an IQ above 140 by that test were included in the study.

There were 643 children in the main study group. When the students who could be contacted again (503 students) were retested at high school age, they were found to have dropped 9 IQ points on average in Stanford–Binet IQ. More than two dozen children dropped by 15 IQ points and six by 25 points or more. Yet parents of those children thought that the children were still as bright as ever, or even brighter.

“Twelve even dropped below the minimum for the Terman study, and one girl fell below 104, barely above average for the general population. … Interestingly, while his tests measured decreases in test scores, the parents of the children noted no changes at all. Of all the parents who filled out the home questionnaire, 45 percent perceived no change in their children; 54 percent thought their children were getting brighter, including the children whose scores actually dropped.” — From Shurkin, Joel (1992). Terman’s Kids: The Groundbreaking Study of How the Gifted Grow Up. Boston (MA): Little, Brown. ISBN 978-0-316-78890-8. Lay summary (28 June 2010), pp. 89–90, citing Burks, Jensen & Terman, The Promise of Youth: Follow-up Studies of a Thousand Gifted Children 1930.

I have much more on this topic, if you are interested.

On studying brain chemistry

Stefan Molyneux interviews Dr. Robert Whitaker, author of Anatomy of an Epidemic: https://www.youtube.com/watch?v=pm77RQdtpSY (Or available as a podcast here: http://bit.ly/anatomyofepidemic)

Ben Swann

Ben’s report on the hypocrisy of the federal government’s position on medical Cannabis: Feds Say Cannabis Is Not Medicine While Holding The Patent on Cannabis as Medicine https://www.youtube.com/watch?v=zuX9y0hiqWE

Weed vs. Alcohol

Plus other interesting Cannabis facts: https://www.youtube.com/watch?v=zGSzj7ztszI

Finally, I do not recommend that teens smoke pot or tobacco; drink alcohol or pop; consume too much sugar or white flour products. I have a million other healthy recommendations for teens but they don’t listen, they know everything and they are immortal. The best we can do is slip in a little education here and there. Real education, not lies and propaganda. Once you lie to a teen, you are toast. Don’t do it.

</end of my response> Following are the studies she sent, along with my comments on each.

Dr. CA’s studies on Cannabis and Teen IQ

Pope, H. G., Gruber, A. J., Hudson, J. I., Cohane, G., Huestis, M. A., & Yurgelun-Todd, D. Early-onset cannabis use and cognitive deficits: what is the nature of the association? Drug Alcohol Depend 2003; 69(3), 303-310. http://www.ncbi.nlm.nih.gov/pubmed/12633916

CONCLUSIONS: “Early-onset cannabis users exhibit poorer cognitive performance than late-onset users or control subjects, especially in VIQ, but the cause of this difference cannot be determined from our data. The difference may reflect (1). innate differences between groups in cognitive ability, antedating first cannabis use; (2). an actual neurotoxic effect of cannabis on the developing brain; or (3). poorer learning of conventional cognitive skills by young cannabis users who have eschewed academics and diverged from the mainstream culture.”

MY COMMENTS: I agree that the cause of the differences cannot be determined from their data.


Gruber, S. A., Sagar, K. A., Dahlgren, M. K., Racine,M., & Lukas, S. E. . Age of onset of marijuana use and executive function. Psychol Addict Behav 2012; 26(3), 496. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3345171/

“We hypothesized that overall, MJ smokers would perform more poorly on tasks of cognitive function than non-MJ smoking control subjects and that individuals who started smoking MJ prior to age 16 would have more difficulty on the tasks relative to those who started later.”

MY COMMENTS: 62 people from Boston in their 20s | 8 tests over two visits | data dependent on the truthfulness and memories of participants | study set out to prove hypothesis which makes it scientifically invalid | lots of “mays”, “mights” and conclusions based on a shaky foundation | uses equally shaky data from former studies. This study is hardly representative or conclusive.


Moffitt TE, Meier MH, Caspi A, Poulton R. Reply to Rogeberg and Daly: No evidence that socioeconomic status or personality differences confound the association between cannabis use and IQ decline. Proc Natl Acad Sci U S A. 2013 Mar 12; 110(11): E980-2. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3600438/

PROVING CAUSATION: “Observational studies like ours cannot prove causation, and yet many important research questions, including whether cannabis alters cognitive function, are intractable to experimentation. It is unethical to randomly assign youngsters to use cannabis for years, to test whether such use impairs mentation. However, even if experimentation were ethical, it could merely show that cannabis has potential capacity to impair cognition. Only a population-representative observational study tests whether cannabis actually is impairing cognition in the real world and how much (7). Certain methodological strategies can help observational studies examine causal hypotheses (8). None of these strategies is sufficiently persuasive, but each augments inference. By incorporating them, we aimed to push the Dunedin Study as far toward causal inference as possible, while acknowledging in our paper the inherent limits of its correlational design. First, our prospective design established temporal sequence: the putative cause, cannabis, preceded the putative outcome, cognitive function. Second, we tested for dose–response contingency; the younger the cannabis user and the more years of use, the worse the cognitive outcome. Third, we compared each participant’s cognitive scores at age 38 y to their former scores on the same tests taken up to age 13 y, a within-individual change design that controls for any and all influences occurring during childhood. Scores decreased from childhood testing to repeat testing at age 38 y among young-onset persistent cannabis users but not among age peers. Fourth, we checked that the finding was not limited to the way we measured cognitive outcomes; persistent cannabis users’ friends and family also noticed the cognitive problems. Fifth, we ruled out plausible artifactual explanations; the effect of cannabis on cognition was not an artifact of other substances abused, schizophrenia, or current cannabis use. Finally, we attempted to rule out rival causal explanations, i.e., factors occurring after age 13 y that might account for the IQ drop. Many young cannabis users opted out of education, but that did not account for their IQ drop. It is imperative to rule out alternative explanations in observational studies, but doing so must be justified by a theoretical rationale; in fact, statistical control for confounders “is not, contrary to the usual belief, ‘playing it safe’, since under several plausible assumptions such control will generate misleading results” (9). In any event, SES and conscientiousness were raised as potential explanations (2, 4), but here we show they did not account for the finding.”

MY COMMENTS: That is a lovely admittance that the findings are not and cannot be conclusive. There are simply too many uncontrolled variables. Correlation is not causation. If you think it is, perhaps we can talk about vaccines next.

More on the Dunedin Study here: http://www.drugpolicy.org/blog/does-marijuana-kill-brain-cells


Solowij, N., Jones, K. A., Rozman, M. E., Davis, S. M., Ciarrochi, J., Heaven, P. C., et al. Verbal learning and memory in adolescent cannabis users, alcohol users and non-users. Psychopharmacology (Berl) 2011; 216(1), 131-144. http://www.ncbi.nlm.nih.gov/pubmed/21328041

“We hypothesised that there would be specific effects of Cannabis compared to alcohol and that the poorest performance would be observed in adolescents with the greatest exposure to Cannabis and who had commenced using regularly at a young age.” [http://link.springer.com/article/10.1007%2Fs00213-011-2203-x]

MY COMMENTS: Their hypothesis gives away their bias. Statistically, you get the result you seek.


Lorenzetti V, Solowij N, Fornito A, Lubman DI, Yucel M. The association between regular cannabis exposure and alterations of human brain morphology: an updated review of the literature. Curr Pharm Des. 2014; 20(13): 2138-67. https://www.researchgate.net/publication/247154316_The_Association_between_Regular_Cannabis_Exposure_and_Alterations_of_Human_Brain_Morphology_An_Updated_Review_of_the_Literature

“However, the evidence for an association between brain morphology and cannabis use parameters was mixed. Further, there is poor evidence for an association between measures of brain morphology and of psychopathology symptoms/neurocognitive performance. Overall, numerous methodological issues characterize the literature to date. These include investigation of small sample sizes, heterogeneity across studies in sample characteristics (e.g., sex, comorbidity) and in employed imaging techniques, as well as the examination of only a limited number of brain regions. These factors make it difficult to draw firm conclusions from the existing findings. Nevertheless, this review supports the notion that regular cannabis use is associated with alterations of brain morphology, and highlights the need to consider particular methodological issues when planning future cannabis research.”

MY COMMENTS: After outlining many of the problems with the studies they studied, the authors somehow support “the NOTION that regular Cannabis use is associated with alterations of brain morphology”? That’s not science, that’s opinion. They are exactly right about one thing: everyone studying Cannabis needs to address the glaring problems when planning the study.


Bossong MG, Jager G, Bhattacharyya S, Allen P. Acute and non-acute effects of cannabis on human memory function: a critical review of neuroimaging studies. Curr Pharm Des. 2014; 20(13): 2114-25. http://www.ncbi.nlm.nih.gov/pubmed/23829369

“Overall, results of these studies show that cannabis use is associated with a pattern of increased activity and a higher level of deactivation in different memory-related areas. This could reflect either increased neural effort (‘neurophysiological inefficiency’) or a change in strategy to maintain good task performance. However, the interpretation of these findings is significantly hampered by large differences between study populations in cannabis use in terms of frequency, age of onset, and time that subjects were abstinent from cannabis. Future neuroimaging studies should take these limitations into account, and should focus on the potential of cannabinoid compounds for treatment of cognitive symptoms in psychiatric disorders.”

MY COMMENTS: Yep.


Jacobus J, Tapert SF. Effects of cannabis on the adolescent brain. Curr Pharm Des. 2014; 20(13): 2186-93. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3930618/

“More adolescent longitudinal studies are still needed to understand both pre-existing differences as compared to discrepancies that develop post-initiation of use. Large longitudinal research would also help clarify the degree to which pre-existing differences and/or chronic marijuana use during adolescence contributes to the development of psychiatric disorders and cognitive impairment in adulthood. Furthermore, we need to better understand the interactive relationships between alcohol and marijuana use as these substance are commonly used together and may result in differing structural, functional, and cognitive brain changes when used alone or in combination.”

MY COMMENTS: Yep ^ ^ ^. This is again a study of studies with admitted problems in the study’s designs. This could hardly be more inconclusive.


Ashtari M, Avants B, Cyckowski L, Cervellione KL, Roofeh D, Cook P, Gee J, Sevy S, Kumra S. Medial temporal structures and memory functions in adolescents with heavy cannabis use. J Psychiatr Res. 2011 Aug; 45(8): 1055-66. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3303223/

“These findings, after an average 6.7 month [although some as little as 30 days] of supervised abstinence, lend support to a theory that cannabis use may impart long-term structural and functional damage.”

MY COMMENTS: Wow, that’s a leap. The authors go on to state that: “Alternatively, the observed hippocampal volumetric abnormalities may represent a risk factor for cannabis dependence.” The old chicken and egg question: which came first?

Only 28 NY kids in the study. Hardly representative, hardly conclusive. They started with proving the theory that a young person’s hippocampus is affected by Cannabis. Then they quote each other’s studies. This is flawed science, at best.


Schweinsburg AD, Brown SA, Tapert SF. The influence of marijuana use on neurocognitive functioning in adolescents. Curr Drug Abuse Rev 2008; 1: 99-111. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2825218/

“Studies of adolescent heavy users have identified impairments in learning and working memory up to six weeks after cessation, suggesting persisting effects, yet raise the possibility that abnormalities may remit with a longer duration of abstinence.”

“Together, these results suggest that adolescents are more vulnerable than adults to neurocognitive abnormalities associated with chronic heavy marijuana use; however, the impact of preexisting risk factors is unknown.”

MY COMMENTS: Interesting but not conclusive by any measure. A study of studies, including studies on rats. Were they teen rats?


Bray JW, Zarkin GA, Ringwalt C, Qi J. The relationship between marijuana initiation and dropping out of high school. Health Econ. 2000; 9: 9-18. http://www.ncbi.nlm.nih.gov/pubmed/10694756

“The results suggest that marijuana initiation is positively related to dropping out of high school. Although the magnitude and significance of this relationship varies with age of dropout and with other substances used, it is concluded that the effect of marijuana initiation on the probability of subsequent high school dropout is relatively stable, with marijuana users’ odds of dropping out being about 2.3 times that of non-users.”

MY COMMENTS: I have no doubt this is true for most high-school dropouts who smoke pot. I know I wanted to. However, will stopping teens from smoking pot make them more accepting of the low-quality education and prison-like atmosphere of a public school?


Lynskey M, Hall W. The effects of adolescent cannabis use on educational attainment: a review. Addiction 2000; 95: 1621-30. http://www.ncbi.nlm.nih.gov/pubmed/11219366

MY COMMENTS: See the study above this one. Another study of studies.


Fergusson DM, Boden JM, Horwood LJ. Psychosocial sequelae of cannabis use and implications for policy: findings from the Christchurch Health and Development Study. Soc Psychiatry Psychiatr Epidemiol. 2015 Sep; 50(9): 1317-26. http://link.springer.com/article/10.1007/s00127-015-1070-x

Findings: “In general, the findings of the CHDS suggest that individuals who use cannabis regularly, or who begin using cannabis at earlier ages, are at increased risk of a range of adverse outcomes, including: lower levels of educational attainment; welfare dependence and unemployment; using other, more dangerous illicit drugs; and psychotic symptomatology. It should also be noted, however, that there is a substantial proportion of regular adult users who do not experience harmful consequences as a result of cannabis use.”

Conclusions: “Collectively, these findings suggest that cannabis policy needs to be further developed and evaluated in order to find the best way to regulate a widely-used, and increasingly legal substance.”

MY COMMENTS: Said it all in the Findings and Conclusions. There is no conclusive evidence that Cannabis use at an earlier age causes any problems at all.


Fergusson DM, Boden JM. Cannabis use and later life outcomes. Addiction. 2008 Jun; 103(6): 969-76. http://www.ncbi.nlm.nih.gov/pubmed/18482420

MY COMMENTS: Would like to read this study. Too many pertinent details missing to evaluate.


Brook JS, Lee JY, Finch SJ, Seltzer N, Brook DW. Adult work commitment, financial stability, and social environment as related to trajectories of marijuana use beginning in adolescence. Subst Abus 2013; 34: 298-305. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3711606/

MY COMMENTS: Starts with the hypothesis that early use of MJ correlates to future negative life outcomes. Study based on answers by participants, sometimes over the phone. This is science? We’re going to base U.S. public policy on 816 black and Puerto Ricans from Harlem? What was the purpose of studying two minority cultures? Should girls be given more leniency with regard to smoking pot than boys? Are white kids any different? Weird and seems so biased from the start.


Ehrenreich H, Nahapetyan L, Orpinas P, Song X. Marijuana Use from Middle to High School: Co-occurring Problem Behaviors, Teacher- Rated Academic Skills and Sixth-Grade Predictors. J Youth Adolesc. 2015 Oct; 44(10): 1929-40. http://link.springer.com/article/10.1007/s10964-014-0216-6

“Multiple indicators—student self-reports, teacher ratings and high school dropout records—showed that marijuana was not an isolated or benign event in the life of adolescents but part of an overall problem behavior syndrome.”

MY COMMENTS: While reading the conclusions, my recurring thought was, “Well, duh.” I’m sure high school pot smokers had poorer study habits… I know I did.


Arria AM, Caldeira KM, Bugbee BA, Vincent KB, O’Grady KE. The academic consequences of marijuana use during college. Psychol Addict Behav. 2015 Sep; 29(3): 564-75. http://www.ncbi.nlm.nih.gov/pubmed/26237288

“Thus, even accounting for demographics and other factors, marijuana use adversely affected college academic outcomes, both directly and indirectly through poorer class attendance. Results extend prior research by showing that marijuana use during college can be a barrier to academic achievement. Prevention and early intervention might be important components of a comprehensive strategy for promoting postsecondary academic achievement.”

MY COMMENTS: Well, duh. If you are bored and uninterested (and possibly went to college because your parents wanted you to), then, yes, you might smoke pot for entertainment and skip classes. If you skip classes, you are not likely to do well in that class and suffer a decline in GPA. If you don’t have a good GPA, you are likely to suffer the consequences in the job world. And I’m not even a scientist.


Martinez JA, Roth MG, Johnson DN, Jones JA. How Robustly Does Cannabis Use Associate to College Grades? Findings From Two Cohorts. J Drug Educ. 2015; 45(1): 56-67. http://www.ncbi.nlm.nih.gov/pubmed/26224748

“Results showed that even after accounting for other measures of student identity formation and drug use, increased cannabis use was robustly associated with lower grade point average.”

MY COMMENTS: Duh, again. I’m so relieved this study was not free so I don’t have to read the whole thing.


Caldeira KM, Arria AM, O’Grady KE, Vincent KB, Wish ED. The occurrence of cannabis use disorders and other cannabis- related problems among first-year college students. Addict Behav. 2008 Mar; 33(3): 397-411. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2247439/

“A significant proportion of cannabis-using college students meet diagnostic criteria for disorder. Even in the absence of disorder, users appear to be at risk for potentially serious cannabis-related problems. Implications for prevention, service delivery, and future research are discussed.”

MY COMMENTS: I must be getting giddy because I laughed out loud at the first sentence above. A disorder? That’s ridiculous. If I smoke pot in college, I might not attend all my classes and may have trouble focusing during a class I do attend. The same can be said of too much sugar, caffeine or being newly in love/lust. This is not rocket science, nor does it qualify as a disorder in anyone’s mind but a psychologist’s interested in increasing his reach.

</end of Consuela’s studies on Cannabis and Teen IQ>

Would love to know your thoughts, please share them in the comments. Thanks!!! And remember:

You don’t have to have cancer to run for the cure and you don’t have to smoke pot to support medical Cannabis.

Call your KY legislators (800) 372-7181 and demand they come out from under their desks and stand up for patient’s rights, support Senator Perry Clark’s 2017 Compassionate Use bill. Thank you.

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