Marijuana Myths

Marijuana Myths

Welcome to my Marijuana Myth-Busting Campaign

ban marijuanaIt’s time to poke holes in the self-serving propaganda that marijuana or cannabis is a safe, harmless panacea for whatever anyone claims it is.  Parents, if your teen or young adult is having behavioral problems, then according to science, marijuana (THC) will make problems worse or will actually cause them. Warn your child and other parents of young people.  Help stop this misinformation from harming our children’s future.

The following are summaries of research and articles on the use of marijuana or cannabis by children, adolescents and young adults. Links are included when available. This list is being updated regularly as new studies are published.

The dark side of marijuana
Vicki Aldous, Mail Tribune, November 2018

This is a detailed and well-researched article on the evidence that marijuana causes schizophrenic psychosis in young people, which includes ways to reduce risks.  “Researchers estimate 8 to 15 percent of cases of schizophrenia are caused by adolescent marijuana use,” says Dr. John Mahan, Jackson County Mental Health psychiatric medical director. “In other words, if no one was using cannabis, we’d have between 8 and 15 percent fewer cases of schizophrenia…” he says.  Laurel Madrone is the clinical manager of a psychiatric unit at Asante Medical Center in Medford, Oregon, she said “Young people with no history of mental illness themselves or in their families are experiencing delusions and hallucinations.”

Adolescent cannabis use alters development of planning, self-control brain areas
University of Illinois at Chicago, November 2018

Adolescent marijuana use may alter how neurons function in brain areas engaged in decision-making, planning and self-control. “Our evidence suggests that exposure to cannabinoids during adolescence alters brain maturation in the prefrontal cortex,” said Eliza Jacobs-Brichford, study lead author.  “Adolescence is a crucial time for fine-tuning the balance of excitatory and inhibitory neurons in the brain, which combine to control precise patterns of brain activity,” said Jamie Roitman, UIC associate professor of psychology and study co-author. “Substance use as a teenager thus has the potential to disrupt the normal developmental trajectory of the prefrontal cortex, with potentially long-term consequences for decision-making.”

New insights into the neural risks and benefits of marijuana use
Society for Neuroscience, November 2018

Compounds in cannabis can impair or improve memory depending on age or disease. Research underscores both the dangers and the therapeutic promise of marijuana, revealing different effects across the lifespan. Marijuana exposure in the womb or during adolescence may disrupt learning and memory, damage communication between brain regions, and disturb levels of key neurotransmitters and metabolites in the brain. In Alzheimer’s disease, however, compounds found in marijuana, such as the psychoactive compound delta-9-tetrahydrocannabinol (THC), may improve memory and mitigate some of the disease’s symptoms.

One month of abstinence from cannabis improves memory in adolescents, young adults
Schuster RM et al, The Journal of Clinical Psychiatry, October 2018; 79 (6) DOI: 10.4088/JCP.17m11977

A new study finds that one month of abstaining from cannabis use resulted in measurable improvement in memory functions important for learning among adolescents and young adults who were regular cannabis users.  Researcher Randi Schuster, PhD, in the Massachusetts General Hospital Department of Psychiatry, said there were actually two important findings “The first is that adolescents learn better when they are not using cannabis. The second — which is the good news part of the story — is that at least some of the deficits associated with cannabis use are not permanent and actually improve pretty quickly after cannabis use stops.”

Cannabis crimps teen cognitive development
B. Jancin, Clinical Psychiatry News, October 2018

What has greater detrimental effect on adolescent cognitive development, alcohol or cannabis?

Patricia Conrod, PhD, who led the large population-based study that addressed the question said, “Generally, we found no effect of alcohol on cognitive development, which was a huge surprise to us.  But ...we found rather significant effects of cannabis use on cognitive development.”  Cannabis use proved to have detrimental effects on all four cognitive domains assessed in the study:  working memory, perceptual reasoning, delayed recall, and inhibitory control.

Cannabis Use in Bipolar Disorder Presents a Treatment Challenge
from:  N. Bally et al, Journal of Affective Disorders, 2014

Cannabis use can cause mood instability and psychosis in those with bipolar disorder.  Researchers have found that cannabis use at a younger age is associated with the onset of the first manic episode; increased manic and depressive episodes; increased risk of rapid cycling; poorer outcome; and poorer treatment compliance.  The relationship between mania onset and cannabis use, are “undeniably correlated,” according to researchers on this study.

Cannabis: It matters how young you start
Canadian Journal of Psychiatry, May 18, 2018

girl smoking weed“Researchers find that boys who start smoking pot before 15 are much more likely to have a drug problem at 28 than those who start at 15 or after.”

“Educate kids early, in primary school, about the risks of starting pot smoking, especially now that the potency is much greater than it was in decades past and that public acceptance is being spurred by legalization in jurisdictions such as Canada” and several states in the U.S.  Explain the facts about how pot causes brain problems; sow mistrust in the pervasive messages that it is safe; avoid using pot yourself so as not to appear hypocritical.  Even if your child just postpones use for a few years, it’s still less problematic and less damaging to their brain.  They need every last brain cell.

Normal SPECT scan
Underside of normal brain.
teenage brain after heavy marijuana use
Brain of 18-year-old after 3 years of daily marijuana use. Holes are brain regions not receiving blood supply.

Americans’ view of marijuana is rosy, and unscientific 
Reuters, July 23, 2018

A nationally representative online survey of 16,280 U.S. adults found that many ascribe health benefits to marijuana or cannabis that haven’t been proven, researchers report in Annals of Internal Medicine.  “The American public has a much more favorable point of view than is warranted by the evidence,” said the study’s lead author, Dr. Salomeh Keyhani of the University of California, San Francisco… Perhaps most concerning is that they think that it prevents health problems.”

  • “Keyhani suspects that a big part of the problem is that there is little, if any, regulation of cannabis advertising. “It’s a multi-billion dollar industry,” she said. “That’s big business.”**
  • “Another part of the problem is that Americans seem to conflate legality with safety…”

**Pharmaceutical companies once freely promoted dangerous drugs as safe even when there was proof they were harmful.  New regulations in the U.S. now require all advertisements include complete information about known side-effects.  This is not done with marijuana/cannabis.

Proof cannabis DOES lead teenagers to harder drugs
Daily Mail, London U.K., June 7, 2017

“The study of the lives of more than 5,000 teenagers produced the first resounding evidence that cannabis is a gateway to cocaine, amphetamines, hallucinogens and heroin.”  “Teenagers who regularly smoke cannabis are 26 times more likely to turn to other drugs by the age of 21.  It also discovered that teenage cannabis smokers are 37 times more likely to be hooked on nicotine and three times more likely to be problem drinkers than non-users of the drug.”

Why do we so consistently underplay the links between cannabis and psychosis?
Patrick Cockburn, Co-author of “Henry’s Demons: Living With Schizophrenia, A Father and Son’s Story,” June 22, 2018

boy smoking marijuana“What is really needed in dealing with cannabis is a “tobacco moment,” as with cigarettes 50 years ago, when a majority of people became convinced that smoking might give them cancer and kill them. In The Lancet Psychiatry, a study concludes that “the risk of individuals having a psychotic disorder showed a roughly 3 times increase in users of skunk** cannabis, compared with those who never used cannabis”.

“Mental health professionals have long had no doubts about the danger. Sir Robin Murray, professor of psychiatric research at the Institute of Psychiatry in London, said that studies showed that “if the risk of schizophrenia for the general population is about 1%, the evidence is that, if you take ordinary cannabis, it is 2%; if you smoke regularly you might push it up to 4%; and if you smoke ‘skunk’ every day you push it up to 8%”.

**”skunk” is a term used in Britain which refers to very high potency marijuana

How cannabis and cannabis-based drugs harm the brain 
Mouro, Ribeiro, Sebatião (Portugal) and Dawson (UK), Journal or Neurochemistry, August 2018

In a study on mice, results showed that “mice exposed for long-term to the drug (cannabinoid WIN 55) had “significant memory impairments.”  Mice could not discriminate between a familiar and unfamiliar object.  “Brain imaging showed that the drug impairs function in key brain regions involved in learning and memory. Moreover, the long-term exposure to the drug impairs the ability of these regions to communicate with each other, suggesting that this underlies the negative effects of the drug on memory.”

Legal cannabis laws impact teen use
The Geisel School of Medicine at Dartmouth, NH, June 27, 2017

‘A new study has found that adolescents living in medical marijuana states with a plethora of dispensaries are more likely to have tried new methods of cannabis use, such as edibles and vaping, at a younger age than those living in states with fewer dispensaries. ” …As cannabis legalization rapidly evolves, in both medical and recreational usage, understanding the laws’ effect on young people is crucial because this group is particularly vulnerable to the adverse effects of marijuana and possesses an inherent elevated risk of developing a cannabis disorder.  …”One study in The Lancet Psychiatry concludes that “the risk of individuals having a psychotic disorder showed a roughly three times increase in users of skunk**-like cannabis, compared with those who never used cannabis”.

Marijuana Can Permanently Lower IQ in Teens
Duke University and King College (London), August 2012

Credit: Daniel G. Amen

Teens who regularly smoke marijuana are putting themselves at risk of permanently damaging their intelligence as adults, and are also significantly more likely to have attention and memory problems later in life, than their peers who abstained, according to a new study conducted by Duke University and London’s King’s College. This study is among the first to distinguish between cognitive problems the person might have had before using marijuana, and those that were caused by the drug.

The research found that adults who started smoking pot as teenagers and used it heavily, but quit as adults, did not regain their full mental powers. In fact, “persistent users” who started as teenagers suffered a drop of eight IQ points at the age of 38, compared to when they were 13.  Researchers noted that many young people see marijuana as a safer alternative to tobacco. A recent “Monitoring the Future” study found that, for the first time, more American high school students are using marijuana than tobacco. Lead researcher Madeline Meier, a post-doctoral researcher at Duke University, said, “Marijuana is not harmless, particularly for adolescents.

marijuana and brain aging

Cannabis use and later life outcomes.
Fergusson DM, Boden JM, Addiction;  Pages: 969-76;  Volume(Issue): 103(6), June 2008

The findings of this study were statistically significant. “Increasing levels of cannabis use at ages 14-21 resulted in lower levels of degree attainment by age 25, lower income at age 25, higher levels of welfare dependence, higher unemployment, lower levels of relationship satisfaction, and lower levels of life satisfaction.”

Risks of increasingly potent Cannabis: The joint effects of potency and frequency
Joseph M. Pierre, MD; Current Psychiatry. 2017 February;16(2):14-20

more marijuana side-effectsCannabis at a young age (age <15 to 18) increases the risk of developing a psychotic disorder.  The accumulated evidence to date is strong enough to view the psychotic potential of Cannabis as a significant public health concern, especially a high-potency Cannabis (HPC) form of hash oil known as Cannabis “wax” or “dabs” that contains as much as 90% THC. Preliminary anecdotal evidence supports the plausibility of hyper-concentrated forms being more psycho-toxic than less potent forms.  Of great concern when it comes to teens, HPC comes in very appealing forms (baked goods, candy, and drinks).

Woody Harrelson quit; What happens to your body after a stoner quits smoking weed.

Woody Harrelson
“…brains of chronic smokers had less gray matter in the orbitofrontal cortex, which means that the part of the brain that deals with decision making and emotional processing had a smaller volume than usual.”

Actor Woody Harrelson was a heavy marijuana user for 30 years, then quit because of what it made him feel like. Dr. Stuart Gitlow and Dr. Joseph Garbely explain what happens to a regular user once they quit.

  • They miss and crave it at first
  • They get anxious
  • They feel feelings again
  • It’s going to be uncomfortable for months, even a year

Marijuana Use Linked with Poor Depression Recovery
J Affect Disord; ePub 2017 Feb 13; Bahorik, et al

Marijuana use is common and associated with poor recovery among psychiatry outpatients with depression a recent study found. Researchers evaluated 307 psychiatry outpatients with depression, and past-month marijuana use for a substance use intervention trial. They found:  Marijuana use worsened depression and anxiety symptoms; it also led to poorer mental health functioning and was associated with poorer physical health functioning.

How cannabis and cannabis-based drugs harm your brain
Francisco M Mouro,et al Chronic, intermittent treatment with a cannabinoid receptor agonist impairs recognition memory and brain network functional connectivity. Journal of Neurochemistry, 2018

marijuana side effects“Long-term use of either cannabis or cannabis-based drugs impairs memory, say researchers. Their study has implications for both recreational users and people who use the drug to combat epilepsy, multiple sclerosis and chronic pain.” 

  • Long-term exposure impairs learning and memory in the animals
  • Brain imaging studies showed that the drug impairs function in key brain regions involved in learning and memory
  • Long-term exposure to the drug impairs the ability of brain regions involved in learning and memory to communicate with each other, suggesting that this underlies the negative effects of the drug on memory

Keeping Teenagers Safe In Vehicles:  Alcohol use is down but marijuana use is up
O’Malley, P. & Johnson, American Journal of Public Health. Nov. 2013, Vol 103, No. 11.

Driving accidents remain the number one cause of mortality among American teenagers. Alcohol use is often involved, and more recently, distracted driving as a result of cell phones is a contributor. A recent analysis has found that drinking and driving has decreased among teenagers, but “using marijuana and driving has increased.”  In this longitudinal study, a sample of 22,000 12th grade students from high schools across the country were questioned over a ten-year period, from 2001-2011. They showed an increase over the 10-year period in either being the driver or passenger of a driver who had just used marijuana. Specifically, 28% reported doing so within the past two weeks.  Marijuana use can impact drivers as much as alcohol.

Link Between Cannabis Use and Psychosis Onset at a Younger Age
Ana Gonzales MD, Santiago Apostol Hospital in Vitoria, Spain, Journal of Clinical Psychiatry. August 2008

blood shot eye 2Researchers found a strong and independent link between cannabis use and the onset of psychosis at a younger age, regardless of gender or the use of other drugs.  The link is related to the amount of cannabis used.  The findings showed a significant gradual reduction in the age at which psychosis began that correlated with an increased dependence on cannabis.

Two articles from this blog

Marijuana is Uniquely Dangerous for Troubled Teens, July 12, 2017

“Marijuana’s effect on adolescents is more serious than many realize, especially for those with behavioral disorders.  This is no exaggeration; marijuana can lead to psychosis and long-term cognitive impairment for your troubled child.  Numerous recent research studies show that marijuana has a more damaging effect on the young brain than is generally understood.”

Marijuana and Psychosis in Teens, May 23, 2010

It’s a myth that marijuana is safe.  While the chemical CBD (Cannabidiol) has proven benefits for certain physical ailments, the chemical THC (tetrahydrocannabinol) has a profound effect on adolescents, especially those with psychiatric vulnerabilities, and its use can lead to psychosis and debilitating long-term cognitive impairment.”

Marijuana Use, Withdrawal, and Craving in Adolescents (summary)
Kevin M. Gray, MD, Assistant Professor in the youth division of the Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina in Charleston.

teen with bloodshot eyesUsing marijuana once per week or more during adolescence is associated with a 7-fold increase in the rate of daily marijuana use in young adulthood.  Cannabis dependence increases the risk factors for impaired driving and delinquent behavior.  Chronic use is associated with impaired immune function, respiratory illnesses, cognitive problems, and motivational impairment. 

Frequent marijuana use during adolescence appears to increase the risk of subsequent development of anxiety and depressive disorders The prevalence of cannabis abuse is 2 to 3 times greater among adolescents who have major depression.  Also linked in both directions: conduct disorder predicts marijuana and other substance use, while early-onset marijuana use predicts conduct disorder.


Withdrawal symptoms are a constellation of emotional, behavioral, and physical symptoms that include anger and aggression, anxiety, decreased appetite and weight loss, irritability, restlessness, and sleep difficulty, which result specifically from withdrawal of marijuana’s psychoactive ingredient, THC.  Less frequent but sometimes present symptoms are depressed mood, stomach pain and physical discomfort, shakiness, and sweating.  Onset of withdrawal symptoms typically occurs within 24 hours of cessation of THC, and symptoms may last days to approximately 1 to 2 weeks.


Marijuana craving occurs when teens get cues associated with marijuana (e.g. sight or smell of the substance, films of drug-taking locations, and drug-related paraphernalia).   Exposure to cues leads to robust increases in craving, along with modest increases in perspiration and heart rate.  Cue reactivity can predict drug relapse.

From the National Institute on Drug Abuse

marijuana infographic

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