Research and citations

We want you to know that the information on our website is based on scientific research. We provide citations for statements made about marijuana below:

The following are citations for the youth consequences of marijuana use:

Using marijuana during adolescence and early adulthood can damage the part of the brain that controls learning and memory. Regular marijuana use can increase the risk of anxiety, depression and psychotic illnesses2.

Research has shown that marijuana’s negative effects on attention, memory, and learning can last for days or weeks after the acute effects of the drug wear off, depending on the person’s history with the drug. (NIDA)

1) Meier MH, Caspi A, Ambler A, et al. Persistent cannabis users show neuropsychological decline from childhood to midlife. Proceeding of the National Academy Sciences U S A. 2012;109(40):E2657-E2664. doi:10.1073/pnas.1206820109.

“Persistent cannabis use over 20 y was associated with neuropsychological decline, and greater decline was evident for more persistent users. This effect was concentrated among adolescent-onset cannabis users, a finding consistent with results of several studies showing executive functioning or verbal IQ deficits among adolescent-onset but not adult-onset chronic cannabis users as well as studies showing impairment of learning, memory, and executive functions in samples of adolescent cannabis users.”

Medical marijuana and cannabinoids have significant potential health risks, such as addiction and worsening of psychiatric illnesses such as some anxiety disorders, mood disorders, psychotic disorders, and substance use disorders, as well as many potential medical benefit. (NIDA)

2) Hill, K. 2015 Medical Marijuana for treatment of chronic pain and other medical and psychiatric problems: A clinical review. Journal of American Medical Association, 313(24), 2474-2483

“Regular marijuana use is associated with an increased risk of anxiety, depression, and psychotic illness, and marijuana use can worsen the courses of these disorders as well”

Marijuana use can lower grades3 and lead to poor school participation3. Opportunities are lost, with 60% of daily marijuana users not completing school4. Marijuana significantly impairs judgment, motor skills, and reaction time5.

3) Fergusson, D.M. et al. (2010). Cannabis and Educational Achievement: Finding from Three Cohort Studies. Drug and Alcohol Dependence, Vol 110, Issue 3, August 2010.

“Pooled estimates suggested that early use of cannabis may contribute up to 17% of the rate of failure to obtain the educational milestones of high school completion, university enrolment and degree attainment. Findings suggest the presence of a robust association between age of onset of cannabis use and subsequent educational achievement.”

4) Edmund Silins, L John Horwood, George C Patton, David M Fergusson, Craig A Olsson, Delyse M Hutchinson, et al. Young adult sequelae of adolescent cannabis use: an integrative analysis. The Lancet Psychiatry, Vol. 1, No. 4, p286–293 (2014)

“We recorded clear and consistent associations and dose-response relations between the frequency of adolescent cannabis use and all adverse young adult outcomes. After covariate adjustment, compared with individuals who had never used cannabis, those who were daily users before age 17 years had clear reductions in the odds of high-school completion (adjusted odds ratio 0·37, 95% CI 0·20–0·66) and degree attainment (0·38, 0·22–0·66), and substantially increased odds of later cannabis dependence (17·95, 9·44–34·12), use of other illicit drugs (7·80, 4·46–13·63), and suicide attempt (6·83, 2·04–22·90).”

5) Hartman RL, Huestis MA. Cannabis effects on driving skills. Clinical Chemistry 2013;59(3):478-492. doi:10.1373/clinchem.2012.194381.

“Cannabis effects include alterations in reaction time (RT), perception, short-term memory, attention, motor skills, tracking, and skilled activities”

The younger marijuana use begins, the greater the likelihood of addiction7.

Marijuana use disorder becomes addiction when the person cannot stop using the drug even though it interferes with many aspects of his or her life. Estimates of the number of people addicted to marijuana are controversial, in part because epidemiological studies of substance use often use dependence as a proxy for addiction even though it is possible to be dependent without being addicted. Those studies suggest that 9 percent of people who use marijuana will become dependent on it rising to about 17 percent in those who start using in their teens. (NIDA)

7) Fergusson DM, Horwood LJ, Lynskey MT, Madden PA. Early Reactions to Cannabis Predict Later Dependence. Archives of General Psychiatry. 2003;60:1033–1039.

“Early subjective responses to cannabis are prognostic of later cannabis dependence. These findings may suggest the presence of genetically mediated individual differences in early responsiveness to cannabis. Clinicians should be aware that young people who report positive reactions to early use of cannabis are at increased risks of later cannabis dependence.”

Here are the citations to the Myth & Facts guide:

Using marijuana during teen years can damage a person’s ability to learn or remember. It may cause a drop in IQ scores, poor grades and increases dropping out of high school.

Research has shown that marijuana’s negative effects on attention, memory, and learning can last for days or weeks after the acute effects of the drug wear off, depending on the person’s history with the drug.

Schweinsburg AD, Brown SA, Tapert SF. The influence of marijuana use on neurocognitive functioning in adolescents. Current Drug Abuse Rev. 2008;1(1):99-111.

“…this review demonstrates that adolescent marijuana users show working memory, attention, and learning abnormalities that persist at least 6 weeks following cessation of use…”

Meier MH, Caspi A, Ambler A, et al. Persistent cannabis users show neuropsychological decline from childhood to midlife. Proceeding of the National Academy Sciences U S A. 2012;109(40):E2657-E2664. doi:10.1073/pnas.1206820109.

“Persistent cannabis use over 20 y was associated with neuropsychological decline, and greater decline was evident for more persistent users. This effect was concentrated among adolescent-onset cannabis users, a finding consistent with results of several studies showing executive functioning or verbal IQ deficits among adolescent-onset but not adult-onset chronic cannabis users as well as studies showing impairment of learning, memory, and executive functions in samples of adolescent cannabis users.”

Macleod J, Oakes R, Copello A, et al. Psychological and social sequelae of cannabis and other illicit drug use by young people: a systematic review of longitudinal, general population studies. Lancet London England. 2004;363(9421):1579-1588. doi:10.1016/S0140-6736(04)16200-4.

“Fairly consistent associations were noted between cannabis use and both lower educational attainment and increased reported use of other illicit drugs.”

Regular marijuana use can make symptoms worse for those with anxiety, depression and psychosis.

Medical marijuana and cannabinoids have significant potential health risks, such as addiction and worsening of psychiatric illnesses such as some anxiety disorders, mood disorders, psychotic disorders, and substance use disorders, as well as many potential medical benefit.

Hill, K. 2015 Medical Marijuana for treatment of chronic pain and other medical and psychiatric problems: A clinical review. Journal of American Medical Association, 313(24), 2474-2483

“Regular marijuana use is associated with an increased risk of anxiety, depression, and psychotic illness, and marijuana use can worsen the courses of these disorders as well”

Regular use can lead to addiction, especially when use starts early.

Marijuana use disorder becomes addiction when the person cannot stop using the drug even though it interferes with many aspects of his or her life. Estimates of the number of people addicted to marijuana are controversial, in part because epidemiological studies of substance use often use dependence as a proxy for addiction even though it is possible to be dependent without being addicted. Those studies suggest that 9 percent of people who use marijuana will become dependent on it rising to about 17 percent in those who start using in their teens.

Lopez-Quintero C, Pérez de los Cobos J, Hasin DS, et al. Probability and predictors of transition from first use to dependence on nicotine, alcohol, cannabis, and cocaine: results of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). Drug Alcohol Dependent. 2011;115(1-2):120-130. doi:10.1016/j.drugalcdep.2010.11.004.

“The cumulative probability estimate of transition to dependence was 67.5% for nicotine users, 22.7% for alcohol users, 20.9% for cocaine users, and 8.9% for cannabis users”

Fergusson DM, Horwood LJ, Lynskey MT, Madden PA. Early Reactions to Cannabis Predict Later Dependence. Archives of General Psychiatry. 2003;60:1033–1039.

“Early subjective responses to cannabis are prognostic of later cannabis dependence. These findings may suggest the presence of genetically mediated individual differences in early responsiveness to cannabis. Clinicians should be aware that young people who report positive reactions to early use of cannabis are at increased risks of later cannabis dependence.”

Marijuana can affect judgment, coordination and reaction time. The risk of being involved in a crash increases after marijuana use.

Marijuana significantly impairs judgment, motor coordination, and reaction time, and studies have found a direct relationship between blood THC concentration and impaired driving ability.

Hartman RL, Huestis MA. Cannabis effects on driving skills. Clinical Chemistry 2013;59(3):478-492. doi:10.1373/clinchem.2012.194381.

“Cannabis effects include alterations in reaction time (RT), perception, short-term memory, attention, motor skills, tracking, and skilled activities”

“Evidence suggests recent smoking and/or blood THC concentrations 2-5 ng/mL are associated with substantial driving impairment, particularly in occasional smokers.”

Hartman RL, Brown TL, Milavetz G, et al. Cannabis effects on driving lateral control with and without alcohol. Drug Alcohol Dependent. 2015;154:25-37. doi:10.1016/j.drugalcdep.2015.06.015.

“SDLP was a sensitive cannabis-related lateral control impairment measure. During drive blood THC ≥8.2μg/L increased SDLP similar to notably-impairing alcohol concentrations. Despite OF’s screening value, OF variability poses challenges in concentration-based effects interpretation.”

Ramaekers JG, Berghaus G, van Laar M, Drummer OH. Dose related risk of motor vehicle crashes after cannabis use. Drug Alcohol Dependent. 2004;73(2):109-119.

“Together these epidemiological data suggests that recent use of cannabis may increase crash risk, whereas past use of cannabis does not”

Li M-C, Brady JE, DiMaggio CJ, Lusardi AR, Tzong KY, Li G. Marijuana Use and Motor Vehicle Crashes. Epidemiological Review. 2012;34(1):65-72. doi:10.1093/epirev/mxr017.

“The results of this meta-analysis suggest that marijuana use by drivers is associated with a significantly increased risk of being involved in motor vehicle crashes.”

Asbridge M, Hayden JA, Cartwright JL. Acute cannabis consumption and motor vehicle collision risk: systematic review of observational studies and meta-analysis. BMJ. 2012;344:e536. doi:10.1136/bmj.e536.

“Acute cannabis consumption is associated with an increased risk of a motor vehicle crash, especially for fatal collisions.”