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This content was developed with extensive input from the Professional Advisory Board of Student Health 101, which includes two physicians and 12 campus health educators and related specialists.
As the federal government considers legalizing recreational marijuana use, the drug is becoming more accessible in Canada. For anyone who’s choosing to use (or considering using) marijuana, it’s important to unravel what this might mean for them. “Like all drugs, using marijuana can be beneficial or harmful depending on how, when, where, in what dosage, in what form, and by whom it is being used,” says Dr. Gerald Thomas, Collaborating Scientist at the Centre for Addictions Research of British Columbia.
If recreational use becomes legal, responsibly using marijuana involves making decisions based on the best information available. What is that best info? Much of what we hear about marijuana comes via sources pushing their own agenda (pro- or anti-legalization). For various reasons, the effects of mind-altering substances, especially illegal ones, are difficult to determine. “The science of marijuana is still developing,” says Dr. Neil Boyd, Professor and Director of the School of Criminology at Simon Fraser University, British Columbia. “Prohibition has generally limited scientific efforts to expand our knowledge of the drug.”
“Extracurricular activities, like sports, can also be impaired, because marijuana can lower your motor coordination skills and your motivation,” says Dr. Ruben Baler, a health scientist at the National Institute on Drug Abuse, Washington DC.
“There is no question that driving under the influence of alcohol raises the risk of an accident, and studies suggest that alcohol and marijuana in combination raises the risk even further,” says Dr. Misch, associate vice chancellor for health and wellness at the University of Colorado School of Medicine. “Marijuana users should not drive for at least three to four hours after getting high.” Some studies have found that using marijuana without alcohol also impairs our driving ability; marijuana, like alcohol, impairs our decision-making skills and reaction times.
What effect does marijuana have on the user’s life?
One size will never fit all. Some people are able to use a lot of pot and have a high quality of life, while others suffer academically or emotionally, or become dependent. “Problematic” use is defined loosely by the impact of marijuana use on an individual. Here’s what to look at:
Tolerance “Excessive cannabis use can lead to a higher tolerance to the effects of the drug (meaning you’ll need to smoke more to get the desired effect), and even symptoms of withdrawal when use is abruptly stopped,” says Dr. Ryan Vandrey, associate professor at the Behavioral Pharmacology Research Unit of Johns Hopkins University School of Medicine, Maryland.
Goals and quality of life “Frequent use of cannabis [can] interfere with attaining goals, tending to responsibilities, and interpersonal relationships, and [even with those negative consequences] it gets harder to quit or reduce use,” says Dr. Vandrey.
Reason for use Using marijuana to cope with anxiety, stress, and other issues carries the risk of dependence and learning problems. In addition, self-medicating can prevent users from developing healthy coping skills (such as exercising, journaling, reading, and talking to friends and family). “I would challenge students to consider why they are smoking [or using marijuana in other ways] in the first place,” says Dr. Jose Valdes, assistant professor of neuropsychiatry at Nova Southeastern University, Florida.
Why “problematic use” is not easy to define
Marijuana affects people differently The amount of money a user spends on marijuana, and even the amount of marijuana consumed, do not align neatly with the impact on users’ functioning, according to a study by researchers at the University of Southern California (presented at the American Public Health Association conference, 2015).
Safety and risk depend on how a drug is used “Safety of a drug is much more complicated than a yes or no question, and whether it is legal/illegal,” says Dr. Vandrey. “There are many medications and products that are legal but are damaging or lethal if used incorrectly or by a person who has an allergy.”
It’s hard to know what causes problematic outcomes Some studies link marijuana use to other risky behaviors or poor outcomes. For example, in a study of college students, the following experiences were associated with using marijuana within the last 30 days: being taken advantage of sexually, not using condoms in sexual encounters, heavy drinking, poor exam performance, missing class, and getting hurt or injured. But correlation is not causation. Maybe marijuana caused bad test scores; maybe students used marijuana in an attempt to cope with bad test scores; or maybe the students who used marijuana also skipped class, resulting in bad test scores. Researchers are working to figure out cause and effect.
Source: Correlates and predictors of marijuana use among US undergraduates. In 143rd APHA Annual Meeting and Exposition (October 31–November 4, 2015).
Signs of problematic marijuana use
Signs of a marijuana use disorder include certain health problems and failure to meet goals and responsibilities at school or work.
- Wanting marijuana and/or being high much of the time
- Needing increased amounts of marijuana to maintain the desired effects
- Withdrawal symptoms (e.g., mood or sleep changes)
- Using marijuana in combination with alcohol and/or other drugs
- Using marijuana to the point that it negatively affects life and functioning (e.g., driving under the influence or social withdrawal)
- Using marijuana to cope with anxiety, stress, insomnia, or other issues
- Using high-potency forms of marijuana, such as hash oil extracts and concentrates (sometimes called “wax” or “shatter”)
Nearly three in ten marijuana users had a marijuana use disorder in 2012–13, according to a 2015 study in the Journal of the American Medical Association.
Marijuana use may increase alcohol risk
Marijuana users may be more likely to develop an alcohol use problem, recent research suggests. Marijuana users are five times more likely than non-users to abuse alcohol or become dependent on it, according to a 2016 study in Drug and Alcohol Dependence. In adults with an existing alcohol use disorder, using marijuana was associated with ongoing drinking problems; the adults who did not use marijuana appeared better able to abstain from alcohol, the same study suggests.
For help with problematic substance use, make an appointment with student health or counseling services on your campus.
Long-term, frequent marijuana use starting in adolescence or early adulthood may impair the brain chronically and irreversibly—or it may not. That uncertainty speaks to the difficulties inherent in researching the effects of substance use.
If marijuana can cause long-term harms, those effects likely vary according to when the individual started using, how much and how often they used, how recently they used, the potency of the marijuana used, and other factors.
Marijuana may affect IQ
In a 2012 study of New Zealanders, those who started using marijuana heavily in adolescence experienced an average decline of 8 IQ points by age 38 (non-users experienced an average 1 IQ point increase over the same time span). The IQ drop persisted even after the users quit marijuana. The participants who started using marijuana as adults did not experience the same IQ decline, suggesting that marijuana use may have neurotoxic effects during critical developmental stages (Proceedings of the National Academy of Sciences).
Marijuana may affect life outcomes
Chronic marijuana use is associated with life setbacks, research suggests. A 2003 study compared frequent marijuana users with their peers from similar socioeconomic backgrounds who reported much less marijuana use. The frequent users were less likely to have graduated from college and had lower incomes, according to Psychological Medicine (2003). The frequent, chronic users believed that marijuana was to blame for their ongoing struggles.
But we don’t know for sure
These research findings are difficult to interpret. It’s possible that other factors explain the effects. For example, maybe the people who used marijuana heavily also used alcohol or other potentially harmful substances, or routinely skipped class as teens, resulting in lower IQ scores later. Which comes first? Maybe less motivated people use more marijuana, rather than marijuana causing that loss of motivation.
In states that have legalized the medicinal and/or recreational use of marijuana, college administrators may feel caught between state and federal law. If a college allows marijuana use, it may risk losing federal funding. Some colleges are exploring exemptions that could allow medical use on campus.
On the upside, for students who are interested in grappling with these issues constructively, this is a good time to get involved. “The reality is that students need to be at the table with the administration and faculty to come up with policies around marijuana use,” says Dr. Seamon.
Real concerns remain. Getting caught using marijuana can narrow your opportunities in various ways:
- Academics Any student convicted of a drug offense while receiving federal student grants or loans can temporarily or permanently become ineligible for federal aid.
- Athletics Drug policies around testing and penalties for college athletes vary from school to school. Under National Collegiate Athletic Association rules, testing positive for marijuana at a bowl game or postseason championship can result in a half-season suspension. The NCAA is reported to be reviewing this policy and moving toward a rehabilitative (rather than penalizing) response to marijuana use.
- Employment Some employers conduct drug tests as part of their hiring process, most typically for lower-skill jobs. THC can be detected in your system using a urine test for up to 12 weeks after usage (depending on how much and how often you use). Some companies also drug test their employees.
- Driving Driving under the influence of marijuana is illegal. If you’re caught you could get fined, lose your license, or do jail time. In some states drivers can be penalized for having traces of marijuana in their blood, even if they are not impaired.
Is moderate marijuana use safer than drinking?
“The key to using marijuana responsibly is to consume it in moderation, in ways that do no harm to oneself or others,” says Dr. Ethan Nadelmann, executive director of the Drug Policy Alliance, which advocates for evidence-based drug policy.
Marijuana effects are highly variable
The effects depend on its potency, the method of delivery, and how it is used (where, why, how often, etc).
Moderate use is not clearly defined
“For marijuana, I advise (for those who choose to use) smaller doses of lower potency preparations, less frequently. That may mean several hits from a joint once or twice a week, ” says Dr. Davis Smith, a practicing internist based in Connecticut and medical director of Student Health 101. (Yes, this is still vague; it’s difficult to determine potency or define a hit. The absence of clarity is a reason to be cautious.)
It makes sense to avoid edibles and resins
Dried marijuana (the flowering tops and leaves of plants) is generally less potent than hashish (dried and compressed resin extracts) and hash oil extracts. Edibles take longer to have an effect on the user, and the quantity consumed is trickier to control (compared to smoking), increasing the likelihood of overuse.
It’s difficult to compare marijuana and alcohol for safety
Any comparison with alcohol depends on the potency of the substances, how they are consumed, and other factors. “Infrequent, small consumption of THC [the component of cannabis responsible for most of its psychological and physiological effects] is, in most cases, unlikely to be more harmful than low-risk alcohol use (e.g., a couple of beers twice a week),” says Dr. Smith. “It is probably less harmful than heavy alcohol use, especially when you factor in the risks that can come with alcohol, like fighting, vandalism, vomiting, etc.” (Until we have a better understanding of marijuana’s effects, this type of comparison is tentative.)
Frequent, heavy THC consumption appears harmful
Researchers are working to better understand what that harm looks like. The risks of alcohol are better researched than the risks of marijuana. Emerging research in states that have legalized marijuana use, such as Colorado, is revealing increased emergency room visits and traffic accidents related to marijuana use.
Your brain on pot now: Your mood
When marijuana feels awe-ful
For many people, marijuana feels good. Some find marijuana helps them relax or feel more enthusiastic about life. They may express themselves more freely or feel more empathic, potentially deepening their social bonds. For some, marijuana heightens sensory experiences (e.g., food tastes better) and creative thinking.
When marijuana feels awful
“Pleasant experiences with marijuana are by no means universal,” says Dr. Ruben Baler, health scientist at the National Institute on Drug Abuse, Washington DC. “Instead of relaxation and euphoria, some people will experience anxiety, fear, distrust, or panic. These effects are more common when too much is taken, the marijuana has an unexpectedly high potency, or when a user is inexperienced.”
When is euphoria a red flag?
“Some users are primed to have an especially fabulous experience of substance use; they have very receptive reward centers in their brains,” says Dr. Smith. “Such individuals are at much greater risk of developing substance use disorders. Starting later reduces that risk. Those with strong family history of substance abuse may be especially good candidates for abstinence.”
Your brain on pot now: Your grades
There is clear evidence that marijuana impairs memory and learning during use and for several days afterward. “Students who go to class high are not getting their money’s worth,” says Dr. Misch.
As use increases, so does risk. “The more a person uses marijuana, the more there are well-documented decreases in attention, concentration, and memory,” says Dr. Jason Kilmer, assistant professor of psychiatry at the University of Washington.
What does heavy use mean for students? “Daily marijuana users may find themselves consistently intellectually impaired. For near-daily or daily users, even stopping for several days may not lessen the intellectual impairment,” says Dr. Misch.
Right side of the law
Federal laws around marijuana remain relatively strict. Students who use marijuana risk a range of negative consequences. Young people, especially those of color, are disproportionately targeted by law enforcement for marijuana-related crimes, an ACLU study showed (2013).
Your state may allow medical use, recreational use, both, or neither. Wherever you live, it is important to “understand the laws and work within the letter of the law,” says Dr. Seamon. For info on what your state allows, see Find out more.
If you show signs of problematic marijuana use, consider seeking confidential support from campus health and counseling services.
Ruben Baler, PhD, health scientist, National Institute on Drug Abuse, Washington, DC.
Jason R., Kilmer, PhD, assistant professor, psychiatry and behavioral sciences; assistant director, Health and Wellness for Alcohol and Other Drug Education, University of Washington.
Donald Misch, MD, associate vice chancellor for health and wellness, associate professor, University of Colorado School of Medicine.
Ethan Nadelmann, JD, PhD, executive director, Drug Policy Alliance.
Marsha Rosenbaum, PhD, director emerita, Drug Policy Alliance (San Francisco office); author, Safety First: A Reality-Based Approach to Teens, Drugs and Drug Education (Drug Policy Alliance, 2014).
Matthew J. Seamon, PharmD., chair and associate professor of pharmacy practice, Nova Southeastern University, College of Pharmacy, Florida.
P. Davis Smith, MD, internist, director of health services, Westminster School, Simsbury, Connecticut; medical director, Student Health 101.
Lori Holleran Steiker, PhD, ACSW, associate professor, University Distinguished Teaching Professor, University of Texas at Austin School of Social Work.
Jose Valdes, PharmD, BCPP, assistant professor, neurology and neuropsychiatry, Nova Southeastern University College of Pharmacy, Florida.
Ryan Vandrey, PhD, associate professor, Behavioral Pharmacology Research Unit, Johns Hopkins University School of Medicine, Maryland.
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