Marijuana and the Teen Brain: How Prohibition Encourages Kids to Use Cannabis

By Clint Werner The opponents of marijuana legalization are running out of justifications for using the power of law enforcement to ruin the lives of those who enjoy the substance but they continue to fan the dying embers of reefer madness hysteria with alarms about how policy reform will lead to an epidemic of teen brain degeneration. And yet, if their true goal is to reduce the prevalence of marijuana use among adolescents, standing firm against legalization could undermine the success of their efforts by affording marijuana the type of novel and manageable risk status that has strong appeal to the teen brain. Many of the assumptions held by theorists on how the teenage brain develops have been proven incorrect or incomplete by a series of MRI scans conducted by the National Institutes of Health on over one hundred adolescents in the 1990s. Although the brain has reached 90 percent of its physical size by about the age of 6 years-old, the internal structure of the brain undergoes dynamic changes during the adolescent years. The imaging has shown that the adolescent brain does not develop in a linear and balanced manner but that there is a disparity of maturation between the prefrontal and subcortical regions of the organ. It seems that maturation proceeds from back to front during the teenage years which explains the frequently irrational behavior that puzzles and vexes adults during this time. As teens mature, they experience a rapid development and activation of the region of the brain that governs rewards and emotions while the region that regulates our sense of impulse control, gratification delay and rational thinking remains immature. The angst of adolescence is largely a result of the awkward and difficult effort to coordinate emotions and behavior into the greater social and intellectual environment. This behavior involves irregular development between emotional impulsivity and impulse control that frequently appears to mimic psychopathology. These awkward feelings and impulses serve to trigger independence and novelty-seeking behaviors that too frequently result in suboptimal decisions that can lead to injuries, violence, unintended pregnancies, STDs and substance abuse. While developments that increase these kinds of risks might seem to defeat the evolutionary drive for survival, they actually serve the valuable purpose of propelling young people out of the family home into independence in society. The impulsivity and increase in risk taking serve a purpose because “leaving home is a high-risk behavior.” There seems to be universality to this behavior because, according to the researchers who conducted the NIH study, “during adolescence, independence-seeking behaviors are prevalent across species.” Unfortunately, for those who cite concerns over adolescent marijuana use as a reason to maintain criminalization or to move toward a Cold War on pot in which everyone is screened and forced into “treatment,” this type of response may very well prime young people to seek out marijuana. The laws against marijuana make it a more novel substance than products that have been integrated into our culture such as alcohol, tobacco and caffeine. The efforts to segregate cannabis out of our society in order to protect children apparently has the opposite effect, giving it an outlaw appeal that is reinforced by the appeal of violating parental approval in independence-seeking behavior. According to the NIH experts, teens are to oblivious to the serious hazards posed by their behavioral choices but their impulse control is over-ridden by emotion and rewards of peer-approval. Using marijuana appeals to this mentality because there is plenty of evidence that the risks are comparatively minor and the novelty appeal is great. The larger marijuana culture, also fostered by criminalization, has a draw for the teen that is looking for a means of expressing independence from the parents. For the thrill-seeking teen, smoking marijuana has outlaw appeal but less risk than stealing a car or picking a fight. A number of papers have asserted that the Netherlands where marijuana distribution is treated as a quasi-legal enterprise, use by teenagers is significantly lower than teen use in the U.S. recent data also shows a drop in teen marijuana use in Arizona since the passage of a medical cannabis law. When marijuana is legalized, the forbidden fruit nature of the substance is mitigated by cultural familiarity. Of course, sensible age restrictions on alcohol maintain an appeal that drives teens to seek them out for abuse, so there is no assertion that legalization would eradicate youthful marijuana use but it would dampen the allure of the forbidden. Many longtime, high profile marijuana advocates have found that their kids have no interest in using marijuana because it is completely novelty-free for them. Ed Rosenthal, the guru of ganja, his son has never been interested in what is his father’s lifelong passion. Keith Stroup, the founder of the National Organization for the Reform of Marijuana Laws (NORML), says that his daughter never smokes cannabis so he has to get high with his son-in-law. The residual reefer madness hysteria that sustains an irrational and counterproductive policy of marijuana criminalization is a self-defeating situation in terms of protecting the kids. Limiting teen access to marijuana is a worthy effort because, despite the lack of harm—and indeed possible benefits—to the adult brain from marijuana use, there may indeed be some impairment to cognition for the rapidly-developing adolescent brain. Julie Holland, M.D., author of The Pot Book, once described teen brain development as similar to a tree that is branching out, expanding connections which then undergo a pruning back phase to tighten up connections. The NIH research reveals that the dendrites—signal-receiving structures—do branch out and the frequently-used synapses grow vital while the lesser-used synapses begin to wither away in a process called “synaptic pruning” which serves the speed and efficiency of the brain. Researchers in Australia, hoping to find some form of brain damage caused by chronic cannabis use, instead were surprised to discover that regular, long-term marijuana smokers experienced a significant increase in functional connectivity in the brain, specifically “greater connectivity between the prefrontal cortex and the occipitoparietal cortex was evident in cannabis users, as compared with controls.” Is it possible that this cannabinoid-driven enhancement of functional connectivity in adult brains impairs synaptic pruning in teens? Neurologist Gary Wenk, Ph.D. has researched the effects of cannabinoids, such as are found in marijuana, on the brain and found positive effects in adults but he cautions that research has shown that “using marijuana prior to age 15 performed more poorly on all aspects of executive function tasks years compared with those who started using marijuana after age 15 or those who had never used marijuana.” Executive function is controlled by the frontal lobes, the ones that mature last and control complex thought, reasoning, planning and impulse control over emotional reactivity. It is encouraging that “scientists did not find differences in executive functioning abilities of people who started smoking marijuana after age 15 as compared to people who had never smoked marijuana.” Unfortunately, the novelty appeal of marijuana’s criminality lures the most vulnerable set of youth into using it when they are most susceptible to habituation. Cannabis is not physically addictive in the way that other drugs such as cocaine and heroin are but one of its great appeals is its ability to heighten the sense of novelty, to alleviate the sense of the mundane and make everyday objects seem fascinating. Raphael Mechoulam, M.D., the Israeli researcher who discovered the structure of the cannabinoids, suggests that one of their functions is to assist the mind in beneficial forgetting so that one does not become overwhelmed by the memories of every face seen and every word heard. This effect contributes to the “Oh wow” effect that marijuana use evokes, wherein everyday objects seem novel and fascinating. For the as-yet-undeveloped adolescent brain which is geared to seek novelty in order to propel the youth into an independent life away from the parental home, marijuana can become a cul-de-sac, a cloister of easily accessed novelty which sabotages the intent of the novelty-seeking brain. If everything in the surrounding environment is transformed into novelty the impulse to seek novelty can be stunted. This could be an underlying explanation for the not entirely unjustified stereotype of the 20 or 30-something stoner living at his parents’ home in the basement. On the other hand, in 2009, researchers published a study which was intended to find out how much harm alcohol and marijuana cause to the brain when used together. The scientists were surprised to discover that binge-drinking teens who smoked marijuana had significant protection from alcohol’s damage to the white matter of their brains when compared to binge drinkers who did not use marijuana. It is clear that any deficit that might occur to the teenage brain from chronic marijuana use does not compare to the devastating damage done by alcohol-poisoning. Another harmful aspect of prohibition is that the threat of imprisonment and the irrational stigma grafted to marijuana through years of propaganda serves to reduce the social contacts of young marijuana users at a time when such experiences are vital for the development social skills. Teenage marijuana users often form cliques that alienate them from the larger arena of social interaction. Some schools conduct marijuana screening and ban users from extracurricular activities, which only compound these problems. Once again, prohibition only serves to aggravate problems with teen marijuana use. The most rational way to approach teen marijuana use is to legalize and normalize adult use, thus making it less appealing as a novel, risk-taking behavior. Also, placing barriers to teen acquisition of marijuana by permitting commercial distribution to adults with penalties for diversion will make marijuana less easily available and will also reduce teen exposure to the illegal polydrug marketplace. One reason that teen cannabis use is lower in the Netherlands, along with the lack of outlaw novelty appeal, is the tight regulation that keeps youngsters out of cannabis shops and eradicates demand for black market street sales of marijuana and hashish. The prohibition zealots are apoplectic that two U.S. states have legalized marijuana and they rail about the threat that this liberalization means to children and warn of a generation of brain dead youth, but sadly, they may be their own worst enemies when it comes to discouraging adolescent use of marijuana.

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Dr. Wenk discusses the effects cannabis use has on the youthful, developing brain and why something that is not harmful to adults can harm teens. This is a good companion piece to the study recently released that showed that regular teen use of marijuana can lower IQ points later in life. In my chapter "Who Should Not Use Marijuana" I suggest that teens not use cannabis. People should wait until they are over 18 y.o. to seek the protective benefits that marijuana offers.  

How chemicals control your thoughts and feelings.

by Gary Wenk, Ph.D. Does it matter when you start smoking marijuana?

Does it matters whether you're a boy or a girl?

Multiple studies during the past few years have shown that adolescence is a period of particular vulnerability for the brain to the effects of many different chemicals and nutrients.  The question that parents often ask is "when is the most vulnerable period?" A recently published study measured the effects of marijuana use upon the cognitive performance of a very large group children who started smoking marijuana daily during their early adolescence, i.e. prior to age 15, as compared to those adolescents who started smoking marijuana after age 15.

Sadly, the researchers were able to recruit an impressive number of young children (104!) who fell into one of these categories. About half of these children had started using marijuana prior to age 15.  They were all tested using a sophisticated set of behavioral tasks that can determine executive functioning abilities.  Executive functioning includes those abilities that we tend to associate most often with complex thought processes. We use executive functioning to perform activities such as organizing our behaviors, planning our next action and controlling our current action (some might call this impulse control), forming strategies, paying attention to important cues in the environment, and remembering details related to what's going in our current environment. The performance of these subjects was compared with the performance of children who had never used marijuana.

The scientists carefully designed their study.  For example, subjects who were diagnosed with a significant mental disorder, were currently using psychoactive medications or had a history of head trauma with loss of consciousness, or were somehow intellectually disabled, were excluded from the study.  The patients in the three groups were carefully matched for the age they started daily marijuana use, their pattern of use, the number of years of daily use and their estimation of lifetime consumption. Finally, they were also matched for their age, years of education and IQ at the time of the testing.

The results were quite interesting.  Those children who started using marijuana prior to age 15 performed more poorly on all aspects of executive function tasks as compared to people who starting using marijuana after age 15 or those who had never used marijuana. Thus, chronic marijuana use prior to age 15 will have far more deleterious effects on complex brain functioning than if one begins using marijuana after age 15. In addition, both males and females who started regular marijuana use prior to age 15 were physically smaller in height and weight; this effect was most dramatic in the males. The effects of marijuana use prior to age 15 were still evident in people who were age 55 at the time of behavioral testing!  Why?

Prior to age 15 the brain is still developing in many substantial ways.  Indeed, that's why these scientists chose this cut-off point for their investigation. Humans have complicated brains that continue to develop and make new connections long after birth. Humans finish developing the most recently evolved brain regions last: that would include the most complex regions of our cortex, particularly the frontal lobes where executive functioning and impulse control is managed.  Overall, these few brain regions are far more vulnerable to any toxin, drug or chemical in our diet. Some regions of the frontal cortex do not finish wiring themselves for service until the early twenties for females and late twenties for males. If you ever wondered why females are charged much lower car insurance rates than males at comparable ages, this is it: the frontal lobes of females are simply "on line" many years before they are in males.

Anything that impairs the normal development of these vulnerable brain regions will impair impulse control, verbal fluency, and complex problem solving.  Furthermore, any impairment in the maturation of these abilities might continue to play a central role in the development of addictive behaviors later in life.  Taken together, these findings suggest that exposure to marijuana during critical periods of brain development will have a long term effect upon higher cognitive functions.

What was also quite surprising was that the scientists did not find differences in executive functioning abilities of people who started smoking marijuana after age 15 as compared to people who had never smoke marijuana!  Therefore, starting marijuana use after age 15 is apparently not as offensive to normal cognitive development.

© Gary L. Wenk, Ph.D. Author of Your Brain on Food (Oxford University Press, 2010)

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Dr. Wenk discusses the effects cannabis use has on the youthful, developing brain and why something that is not harmful to adults can harm teens. This is a good companion piece to the study recently released that showed that regular teen use of marijuana can lower IQ points later in life. In my chapter "Who Should Not Use Marijuana" I suggest that teens not use cannabis. People should wait until they are over 18 y.o. to seek the protective benefits that marijuana offers.  

How chemicals control your thoughts and feelings.

by Gary Wenk, Ph.D. Does it matter when you start smoking marijuana?

Does it matters whether you're a boy or a girl?

Multiple studies during the past few years have shown that adolescence is a period of particular vulnerability for the brain to the effects of many different chemicals and nutrients.  The question that parents often ask is "when is the most vulnerable period?" A recently published study measured the effects of marijuana use upon the cognitive performance of a very large group children who started smoking marijuana daily during their early adolescence, i.e. prior to age 15, as compared to those adolescents who started smoking marijuana after age 15.

Sadly, the researchers were able to recruit an impressive number of young children (104!) who fell into one of these categories. About half of these children had started using marijuana prior to age 15.  They were all tested using a sophisticated set of behavioral tasks that can determine executive functioning abilities.  Executive functioning includes those abilities that we tend to associate most often with complex thought processes. We use executive functioning to perform activities such as organizing our behaviors, planning our next action and controlling our current action (some might call this impulse control), forming strategies, paying attention to important cues in the environment, and remembering details related to what's going in our current environment. The performance of these subjects was compared with the performance of children who had never used marijuana.

The scientists carefully designed their study.  For example, subjects who were diagnosed with a significant mental disorder, were currently using psychoactive medications or had a history of head trauma with loss of consciousness, or were somehow intellectually disabled, were excluded from the study.  The patients in the three groups were carefully matched for the age they started daily marijuana use, their pattern of use, the number of years of daily use and their estimation of lifetime consumption. Finally, they were also matched for their age, years of education and IQ at the time of the testing.

The results were quite interesting.  Those children who started using marijuana prior to age 15 performed more poorly on all aspects of executive function tasks as compared to people who starting using marijuana after age 15 or those who had never used marijuana. Thus, chronic marijuana use prior to age 15 will have far more deleterious effects on complex brain functioning than if one begins using marijuana after age 15. In addition, both males and females who started regular marijuana use prior to age 15 were physically smaller in height and weight; this effect was most dramatic in the males. The effects of marijuana use prior to age 15 were still evident in people who were age 55 at the time of behavioral testing!  Why?

Prior to age 15 the brain is still developing in many substantial ways.  Indeed, that's why these scientists chose this cut-off point for their investigation. Humans have complicated brains that continue to develop and make new connections long after birth. Humans finish developing the most recently evolved brain regions last: that would include the most complex regions of our cortex, particularly the frontal lobes where executive functioning and impulse control is managed.  Overall, these few brain regions are far more vulnerable to any toxin, drug or chemical in our diet. Some regions of the frontal cortex do not finish wiring themselves for service until the early twenties for females and late twenties for males. If you ever wondered why females are charged much lower car insurance rates than males at comparable ages, this is it: the frontal lobes of females are simply "on line" many years before they are in males.

Anything that impairs the normal development of these vulnerable brain regions will impair impulse control, verbal fluency, and complex problem solving.  Furthermore, any impairment in the maturation of these abilities might continue to play a central role in the development of addictive behaviors later in life.  Taken together, these findings suggest that exposure to marijuana during critical periods of brain development will have a long term effect upon higher cognitive functions.

What was also quite surprising was that the scientists did not find differences in executive functioning abilities of people who started smoking marijuana after age 15 as compared to people who had never smoke marijuana!  Therefore, starting marijuana use after age 15 is apparently not as offensive to normal cognitive development.

© Gary L. Wenk, Ph.D. Author of Your Brain on Food (Oxford University Press, 2010)