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Debunking marijuana myths for teens.

The annual checkup has long provided an opportunity for early adolescents to learn about the risks of alcohol and drug use from a trusted source who may be less biased than parents, teachers, or police. Parents also turn to their child's pediatrician for guidance on how to broach this important topic with their children, or they may come with concerns about their children's use of drugs or alcohol.

Marijuana has become an increasingly complex topic, as its legal status has rapidly changed: It's legal to purchase marijuana in four states (Alaska, Colorado, Oregon, and Washington, as well as the District of Columbia); it is decriminalized in 20 states and the District of Columbia for certain marijuana possession offenses; and it is legal to use medical marijuana in 23 states. As its legal status changes, attitudes about its use also have shifted, and its availability, form, and potency all have changed dramatically in just the past decade. Further, we ourselves may have mixed feelings about marijuana use based on our own experience as adolescents and sampling bias. We may have seen its low-level use and minimal effects in young or mature adults, or we may have seen substantial use of marijuana have a major deleterious impact on a friend or become a gateway drug for addiction to dangerous substances.

Before addressing marijuana use with adolescent patients and dealing with their potential skepticism concerning any harm, it is worth spending a little time looking in the mirror to consider your perspective on marijuana use and your response to disbelief.

According to the National Institute on Drug Abuse's Monitoring the Future (MTF) survey, almost 12% of 8th graders, 27% of 10th graders, and 35% of 12th graders in the United States reported having used marijuana in the past year. Among the 12th graders in that 2014 survey, almost 20% were current users of marijuana and 6% were daily users. Many surveys, including the MTF, have demonstrated that attitudes of teenagers have shifted about marijuana's dangerousness, with a steep and steady decline in the number of teenagers believing that regular marijuana use poses a risk to their health and well-being. In 2014, less than 40% of 12th graders in the MTF survey agreed that regular use of marijuana would pose a risk to their well-being, compared with a peak of almost 80% of 12th graders in the early 1990's.

Pediatricians have an opportunity to change their patients' thinking about marijuana. At the checkup when you routinely ask about alcohol and drug use, ask about marijuana use in particular. You might start by asking if they have heard their friends talking about marijuana? What have they heard? Are other kids using it? Have they ever seen anyone use it? Have their friends invited them to try? You should find out if they think it is safe or dangerous, and how it compares with cigarettes, alcohol, and other drugs on this score. Then you may be able to debunk some myths you hear from them.

Myth No. 1: Marijuana is medicine

Although 23 states allow the legal sale of marijuana for "medicinal purposes," it is important to note that there are currently no Food and Drug Administration-approved indications for medical marijuana. There is modest evidence that the active compounds in marijuana (delta-9-tetra-hydrocannabinol [THC] and other cannabinoids) can be effective in the management of the muscle spasticity associated with multiple sclerosis, the treatment of nausea associated with chemotherapy, and increasing the appetite of patients with wasting due to AIDS, and there are FDA-approved synthetic cannabinoids that can be prescribed for these symptoms. It is also important to note that there is no evidence that THC or other cannabinoids are useful in the treatment of mood or anxiety symptoms, even though these are often used as reasons for seeking medicinal marijuana. Indeed, marijuana may cause or worsen several psychiatric problems.

Myth No. 2: Marijuana is safe

Although there is consensus that moderate marijuana use in adulthood poses only limited health risks (including the known risks of smoking), there is robust evidence that marijuana use during youth (through the early 20s) causes several serious and permanent effects on the developing brain. One 2012 study showed that for youth who are dependent on marijuana before they are 18 years, there is an 8-point drop in IQ in adulthood (Proc Natl Acad Sci USA. 2012 Oct 2;109[40]:E2657-64). This IQ drop persists even if they quit smoking, and does not occur for those who first become dependent on marijuana in adulthood. A 2015 study demonstrated that even for adolescents who are light smokers (one to two times weekly) with no evidence of marijuana dependence, there are significant abnormalities in the size and shape of their amygdala and nucleus accumbens, with associated changes in their motivation, decision making, attention, functional memory, and processing of emotions (J Neurosci. 2014 Apr 16;34[16]:5529-38). These abnormalities increase with increased frequency of use, and are not seen in those who begin smoking in adulthood (mid-20s and later).

Beyond these findings of cognitive deficits, evidence is growing that adolescent marijuana use is associated with several psychiatric illnesses, including depression and anxiety. There is especially strong evidence for a causal link between marijuana use and psychotic illnesses in (genetically) vulnerable young people. Any marijuana user can experience a brief psychotic reaction if the amount ingested or smoked is great enough, but for those young people who carry a specific variant of the gene for catechol-o-methyltransferase (COMT, an enzyme that degrades neurotransmitters), smoking marijuana in adolescence nearly triples their risk of developing schizophrenia in adulthood. For youth with a variant of the AKT gene (another enzyme affecting dopamine signaling in the brain), daily use of marijuana raises their risk of developing schizophrenia sevenfold. Clearly, marijuana can be the critical environmental trigger for schizophrenia in genetically vulnerable youth. Until we have a comprehensive knowledge of the relevant genes, and routinely check every patient's complete genetic profile, it is reasonable to assume that any young person using marijuana is significantly increasing the risk of developing schizophrenia, a chronic and disabling condition.

Myth No. 3: Marijuana has no effect on driving

Marijuana intoxication significantly affects motor coordination, reaction time, and judgment, and multiple studies have demonstrated a direct relationship between blood THC concentration and impaired driving ability. A recent meta-analysis demonstrated that the risk of being in a car accident doubled after marijuana use (Drug Alcohol Depend. 2004 Feb 7;73[2]:109-19). These studies usually involved adults, and it is reasonable to assume that the risks may be more pronounced in adolescents, particularly ones who are new to driving or have other problems that could affect their attention or reaction time (such as attention-deficit/hyperactivity disorder). Beyond letting patients know about the increased risks of accidents, it may be worth reminding them that driving while intoxicated--even with legal use marijuana--is a criminal offense.

Myth No. 4: Marijuana has no effect on schoolwork

Aside from the risks of causing long-term cognitive changes and psychiatric problems that can affect school performance, the direct effects of marijuana intoxication can linger and affect school performance well after its use. The "high" from marijuana typically lasts from 1 to 3 hours, but the drug's effects on higher-level cognitive processes (mediated by the neocortex and hippocampus) can last for days. So a teenager who smokes on Saturday night may have lingering impairment of motivation, the ability to shift attention, the ability to learn complex tasks, and working memory. These are all critical cognitive abilities for learning, and can make studying on Sunday and performing well on a test on Monday much more difficult.

Myth No. 5: Marijuana is not addictive

Marijuana is addictive, with studies suggesting that nearly 9% of marijuana users will become addicted. Again, the risks are far greater for young people. Among people who begin using marijuana during adolescence, the rate of addiction climbs to 17%, and can be as high as 50% in daily users. Remember that addiction describes a pattern of continued use despite that use causing significant legal, social, or school and work problems. Users also may develop physical dependence, with a withdrawal syndrome that includes irritability, restlessness, insomnia, and appetite changes; these can last as long as 2 weeks.

Currently available forms of marijuana are much more potent than those that were studied and used in prior decades. On average, the potency of smoked marijuana has tripled, and there are concentrates (in oil form, for example) and hybrids with much higher potency still. More potent marijuana increases the high from even a small dose, and increases the likelihood of addiction and of other immediate and lingering complications of its use. So, parents who think they know what marijuana does to adolescents based on their own youthful experiences are significantly underestimating the risks.

When asking your patients explicitly about marijuana use, be curious and nonjudgmental, but also be frank and forthright about what is known about the risks associated with its use. Although the current legal and political changes around marijuana use may have given them the impression that marijuana use is safe, you want them to have the facts they need to make informed decisions. Even if you only discuss one of these myths with your patients, you will have equipped them with powerful information that they may use and share with their friends.

Dr. Swick is an attending psychiatrist in the division of child psychiatry at Massachusetts General Hospital, Boston, and director of the Parenting at a Challenging Time (PACT) Program at the Vernon Cancer Center at Newton (Mass.) Wellesley Hospital. Dr. Jellinek is professor of psychiatry and of pediatrics at Harvard Medical School, Boston. Email them at


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Author:Swick, Susan D.; Jellinek, Michael S.
Publication:Pediatric News
Date:Jan 1, 2016
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