When Green Means Stop (an update on marijuana use by adolescents)

2017 July 6
by Dr. Steve Sarche

According to the 2016 Monitoring the Future Survey, marijuana usage by American 8th and 10th graders has slightly declined over the last 5 years, while usage by 12th graders has been roughly the same. States with legal medical marijuana have higher rates of adolescent usage than the other states.

Marijuana is basically the name for the dried and shredded leaves and flowers of the cannabis plant. Delta-9-Tetrahydrocannabinol (THC) is the main active ingredient in cannabis, but the plant contains at least 489 chemical compounds, with an estimated 70 cannabinoids (substances that can affect how we feel or affect us cognitively).

Shortly after smoking cannabis, heart rate increases, the bronchial system relaxes and becomes enlarged, and eyes become red as blood vessels expand.   Generally a person will experience feelings of euphoria and relaxation with increased appetite, pain relief, followed by sleepiness.   Some people will experience anxiety and paranoia.

The human nervous system has an endocannabinoid system with cannabinoid receptors (CB receptors). There is an increasing body of literature showing that the endocannabinoid system plays an important role in brain development and maturation (Compton, psychiatry news, 5/20/2016, 10).

The role of the endocannabinoid system in neural development is likely why younger people, especially those under the age of 16, have a much higher risk of negative side effects of using cannabis. The effects of THC are more potent and last longer than the natural neurotransmitter, anandamide, that THC mimics. CB receptors are most abundant in areas of the brain responsible for pleasure, reward, cognition, memory, motor coordination and pain perception.

Marie Banich, a well-known neuroscientist, describes how teens generally lack a mature ability to conceptualize the future, have a high reward and novelty seeking drive, have less self-control, are less organized in their decision making, and more vulnerable to peer pressure.   These are all aspects of executive functioning. Teens additionally are highly responsive to reward over punishment. This means their decisions are driven by now and not later.   As Banich says, they clearly see the carrot but they don’t see the stick as well.

The part of the brain most responsible for executive functioning is the frontal lobe.   The frontal lobe mostly consists of white matter.   White matter is crucial in facilitating communication between different regions of the brain.   White matter tracks develop well into the 20’s. Earlier exposure to drugs or trauma may stunt development of white matter tracks. One study showed that adults exposed to cannabis earlier in life had less developed white matter than non-users (Coloradan, summer 2017, P 25).

Frequent cannabis use has been linked to poorer educational and social outcomes in teens. This includes higher school dropout rates, and overall feelings of inferior life and interpersonal satisfaction. McLeod and colleagues additionally showed that cannabis use is consistently associated with lower grades (Lancet, 2004, 1579-88). Studies have also shown that frequent users tend to have increased absences and accidents at school or work and higher job turnover. The recent proliferation of genetically engineered strains of cannabis have resulted in an increased ratio of THC to other chemicals and that may be what causes even more harm.

Adolescents are particularly prone to other negative effects of cannabis use as well. Acutely, it causes decreased attention, poor concentration, slow reaction times, short-term memory deficits, increased errors in task, and poor fine motor coordination. One study showed that these effects can last at least 28 days after last use (Hall and Degenhardt, Lancet 2009, 1383-1391).

Heavy (daily) use places teens and young adults at the highest risk for these cognitive problems, and ongoing use can evolve to generally slower psychomotor speeds, poor sequencing ability, and difficulties in visual processing and verbal story memory. These findings are backed by functional imaging that has shown lower activity in brain regions involved in memory and attention in chronic cannabis users. Of considerable concern, there is a report that adults who used cannabis at younger ages had ongoing cognitive issues, even after cessation (Gonzalez, Swanson, Pro Natl Acad Sci, 2012, 15970-15971).

On the other hand, Banich has shown that exercise and activities that engage many parts of the brain, such as reading, playing sports and playing music, improve cognitive abilities and overall brain development. She notes that the right or wrong stimulus at the right or wrong time may make or break how a teenager develops, depending on their individual susceptibility to various factors.

Psychiatric side effects, especially for those who start using before age of 16 or for those using heavily at age 21, include depression and anxiety. Additionally, ­­­­­­­­those prone to schizophrenia have an enhanced risk of an episode of acute psychosis.   Heavy cannabis use can also cause earlier onset of psychotic illness. Depending on age of first use and genetic make-up, it is thought that cannabis use can cause a psychotic illness in and of itself. Regular use may also lead to generally poorer outcomes with any psychiatric treatment.

Cannabis can be addictive. There is approximately a 1 in 7 chance that a teenager who uses cannabis will develop an addiction to it. Regular use of cannabis can cause tolerance, psychosocial problems, interpersonal problems, loss of self-control, and diminished productivity. People will continue use despite problems. Cannabis withdrawal has also been identified manifested by irritability, anxiety, insomnia, dysphoria, craving, and appetite changes. These are all characteristics of drug dependency or addiction. There is also an associated gateway effect. It was shown that regular users of cannabis have a 124 times higher risk for initiating other illicit drug use (Mayet, Legleye et al, Addict Behav, 2012, 160-6).

Health risks include cough, bronchitis, and lung infections. Due to elevated heart rate and toxins in smoke, there is a higher risk for cardiovascular problems.   There is evidence that smoked cannabis can contribute to various kinds of cancers. Cannabis smoke does contain toxins found in tobacco smoke such as carbon monoxide and cyanide. While it has been reported that casual use can increase air flow due to bronchial expansion, there may be more lung damage with regular use due to the fact cannabis users tend to inhale more deeply and hold the smoke in longer than tobacco users.

Synthetic cannabinoids, “Spice” or “K2”, are a combination of herbs and chemical compounds similar to THC, but more potent. They gained popularity because they may not be detected in typical urine drug screens. The effects are similar to cannabis, but they are also considered more dangerous as the mixture of substances varies greatly.   Synthetics have the same physical and mental health risks that natural cannabinoids have, but also seizures, increased risk for cardiovascular damage, kidney damage, and a greater risk for psychosis. It is estimated that 1 in 10 high school aged kids in the US have tried this, and the adverse effects can happen after one use.

How do we help teenagers make better decisions about using cannabis (hopefully helping them decide not to)? That is not the scope of this article, but in a nutshell, family support work is important with motivational interviewing, incentive based interventions, and cognitive behavioral therapy (CBT) with focus on building life skills. CBT helps anticipate triggers for use and helps build coping strategies for those.   There is a program at Denver Health for this called the “STEP Program” at 303-602-1893. They do thorough consultations and offer interventions.

If cannabis is being used by your teenager, urge him to keep an eye out not only for the benefits but for any side effects it is causing. Watch for trends in use, especially any increases and the usage of any other substances. Get as many details as possible about what is being used, as well as the volume and frequency of use. Sometimes consequences in the form of punishments are needed, but incentives work better in helping with long-term abstinence.

Keep the discussions open, listen, and make it a conversation, not an argument or lecture.   Work to understand the motivations for his use and help him decide he wants to cut back for himself. Find what incentives would lead to that. As teenagers have less sight of the stick, more of the carrot, they ultimately have to figure out for themselves why it is worth not using.

Although the research shows association, not causation of the problems of cannabis use, I advise teenagers under age 16 across the board that they should not take any chances with using marijuana under any circumstances.

   -Thanks to Douaihy, Cannabis Revisited, UPMC Synergies, Fall 2013.

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