Cannabis and the Brain Discussion Assignment

Cannabis and the Brain Discussion Assignment

Cannabis and the Brain Discussion Assignment

National polls show that 80% of Americans support the medical use of marijuana, and nearly 3 out of 4 support a fine-only (no jail) for recreational smokers. In addition, 58% of Americans favor legalizing marijuana, according to a recent Gallup poll — this is the highest percentage of support ever reported in a nationwide scientific poll.

Since 1996, 23 states and the District of Columbia have enacted laws to legalize medical marijuana. Two states (Washington and Colorado) have legalized controlled recreational use of marijuana. More states are considering legalization for medical purposes. But does the current scientific research on the health benefits and hazards of cannabis use support such legislation?

Nine out of 10 people who meet the clinical criteria for substance use disorders involving nicotine, alcohol, cannabis or other drugs began using drugs before they turned 18. People who begin using any addictive substance before age 15 are six and a half times as likely to develop a substance use disorder as those who delay use until age 21 or older (28.1 percent vs. 4.3 percent).

The increased vulnerability of adolescents to adverse long-term outcomes from marijuana use is probably due to the fact that the brain, including the endogenous endocannabinoid system and especially the frontal cortex, is still developing until around age 25. The frontal cortex is responsible for many higher brain functions such as analysis, judgment, and decision making.

Indeed, early and regular marijuana use statistically predicts increased risk of marijuana addiction, and this in turn predicts increased risk of using other illicit drugs. Compared to those who begin using marijuana in adulthood, persons who begin using in adolescence are 2-4 times as likely to develop cannabis dependence within 2 years of first use. Since legalization will likely mean increased access to marijuana for all age groups, teenagers (and those even younger) will be especially vulnerable to increased dependence and addiction to marijuana.

Prenatal Exposure

A 2014 study found that prenatal exposure to THC disrupts normal cortical development of the axonal connections between brain neurons – in other words, the “miswiring” of neural circuits! This has serious implications regarding the effects of THC on the developing brain. This impairment of the connections between brain neurons is especially evident in areas of the cerebral cortex which are responsible for higher cognitive functions and memory formation (ie. the frontal lobes).

This may help explain the association, found by multiple studies, between frequent use of marijuana during adolescence and significant declines in IQ scores over time. A 2012 study compared child IQ (age 13) to IQ at age 38 in two groups – adolescent onset users and adult onset users. In addition, each group was further divided into two sub-groups: 1) those who were infrequent users at age 38, and 2) those who were still using frequently at age 38.

The results were striking – both sub-groups of adult onset users showed no decline in IQ scores, regardless of whether they were still smoking marijuana at age 38. However, both sub-groups of the adolescent onset users showed significant declines in neuropsychological functioning (as measured by IQ tests), with greater IQ reduction (-8 IQ points) in those who were still smoking marijuana at age 38. The five areas of mental function tested were executive functioning, memory, processing speed, perceptual reasoning, and verbal comprehension.

In the last 5 years, significant advances have been made in understanding how cannabis affects brain

function, though much remains to be learned. The abundance of cannabinoid receptors in the hippocampus, amygdala, basal ganglia, and prefrontal cortex suggests that disruption of the brain’s cannabinoid system by administration of exogenous cannabinoids, like THC, may have important implications for various neurobehavioral processes, including mood and anxiety regulation, learning, memory, motivation, motor control, reward processing, and executive functions.

Recent reports show that fewer adolescents believe that regular marijuana use is harmful to health. At the same time, adolescents are starting cannabis use at younger ages, and more adolescents are using cannabis on a daily basis.

The impairments that follow teen cannabis use discussed above are consistent with research indicating the cannabinoid system plays a prominent role in synapse formation during brain development. Also of interest – animal studies show that prenatal or adolescent exposure to THC can recalibrate the sensitivity of the reward system to other drugs – resulting in an enhanced response to other drugs.