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As marijuana laws become more forgiving in Colorado and other states, marijuana may be more accessible. For anyone who’s using (or considering using) marijuana, it’s important to unravel what this might mean. “Marijuana is a drug. Whether it’s used recreationally or medicinally, it’s going to have an effect,” says Dr. Matt Seamon, associate professor of pharmacy practice at Nova Southeastern University in Florida.

Responsibly using marijuana involves making decisions based on the best information currently 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. “We know less than most people acknowledge,” says Dr. Donald Misch. Here’s what we know—and don’t know—so far.

If you use, here’s how to reduce your risk

Athletics and driving: Marijuana on the field and in the car


“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. “Marijuana users should not drive for at least three to four hours after getting high.” And, if marijuana is consumed in the form of an edible, it can take five or more hours before driving is appropriate. 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 does problematic marijuana use look like?

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 smoked 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.

Help with drug dependence (National Association of Addiction Treatment Providers)

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 support around substance use concerns, visit the CU Collegiate Recovery Center (CUCRC) in UMC 102 or make an appointment with Counseling and Psychiatric Services (CAPS).

Your brain on pot later: What’s up with long-term use?

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.

Marijuana on campus: What it means

Though the state of Colorado has legalized recreational and medicinal marijuana, marijuana possession and use is still prohibited at CU Boulder (including in campus housing), even with a prescription. Additionally, use is only legal for those over the age of 21; underage use is subject to an MIP ticket, fines, and sanctions through the university.

Being under the influence of marijuana (regardless of age) is also a violation of the CU drug policy and may result in student conduct sanctions and processes.

These 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 results in a half-season suspension. The NCAA is reported to be reviewing this policy.
  • Employment Many employers conduct drug tests as part of their hiring process. THC can be detected in the system using a urine test for up to 12 weeks after usage.
  • Driving Driving under the influence of marijuana is illegal.  A DUI from marijuana carries consequences of fines, losing one’s license, or jail time. In some states drivers can be penalized for having traces of marijuana in their blood, even if they are not impaired.

How does your state penalize drivers who use marijuana?

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.

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.”

Frequent, heavy THC consumption is clearly 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.

Impacts on the brain


When marijuana feels awe-ful: For some people, marijuana feels good. They may 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.”

Academics: 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).

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 Colorado and other states allow, see Find out more today.

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