Cannabis

20.02.2021 |

Episode #7 of the course Introduction to drugs and behavior by Dr. Daniel McGrath

 

Welcome back! In this lesson, we are going to cover cannabis, also known as marijuana. Cannabis use is a fascinating topic. Yet, cannabis has also been shrouded in controversy. The debate largely began in the 1930s when a government official named Harry Anslinger directed an organized campaign to vilify cannabis. In 1936, the film Refer Madness was released. It was essentially a propaganda film with wild and inaccurate claims of the supposed dangers of marijuana. These events set the tone for later legislation that outlawed cannabis for 60+ years. Today, the tone has changed dramatically. Many countries around the globe have loosened laws on medicinal and recreational use.

Marijuana comes from a plant called Cannabis sativa, and there are a number of varieties. The primary psychoactive ingredient in cannabis is delta-9-tetrahydrocannabinol (THC), a chemical found throughout the plant. THC is one of 100+ cannabinoids that have been identified. With changes in how the plant is grown, the concentration of THC in cannabis has risen dramatically since the 1960s. In short, today’s strains are much more potent than those smoked by people in the 60’s.

The other prominent cannabinoid is cannabidiol (CBD). Unlike THC, CBD does not have any significant psychoactive effects. However, CBD does appear to interact with THC to enhance its psychoactive effects. On its own, CBD does have medicinal benefits for chronic pain, seizures, and other conditions.

There are many ways that cannabis can be administered. The leaves, stems, and buds of the plant are dried and used in marijuana cigarettes (i.e., joints) and edibles such as being baked into cookies or brownies. Hashish is made with cannabis oil from unpollinated female plants. It has a higher THC content compared to buds. Similarly, dabbing involves heating a cannabis oil extract with a torch or vaping device to inhale aerosolized THC. Vaping is becoming an increasingly popular route of administration; however, smoking the plant is still the most common. Lastly, synthetic cannabinoids (e.g., K2, Spice) are chemicals produced in a lab that is sprayed on dried plant material, which is then smoked. These synthetic drugs are illegal and are far more dangerous than the cannabis plant. They are similar in that they bind to cannabinoid receptors in the brain, but in reality, they are very different drugs compared to marijuana.

When cannabis is inhaled, THC molecules enter the bloodstream through lung tissue. It is estimated that 20% to 30% of THC inhaled is ultimately absorbed. Once in the bloodstream, peak plasma THC levels are reached in about 10 to 15 minutes. In comparison, when cannabis is eaten (e.g., edibles), THC is absorbed through the gastrointestinal tract, where peak blood levels occur in two to three hours. Because of this, some people may think that an edible “isn’t doing anything”, when in reality, they just need to wait for the effects to appear. Metabolism of THC by the liver starts immediately; however, THC has a very long elimination half-life. When smoked, the psychoactive effects will last in the range of 60 minutes, but the elimination of THC molecules can take up to 30 hours. In addition, some THC metabolites can be detected in body fat up to two weeks later, meaning it’s possible to test “positive” for THC on a drug test long after it was smoked.

There are two types of cannabinoid receptors, CB1 and CB2. When THC reaches the brain, it primarily binds to CB1 receptors in many regions linked to memory, executive functioning, and the reward system. When cannabis binds to CB1 receptors, it creates feelings of euphoria, alterations in perception, and relaxation. In the reward system, the actions of THC lead to an increase in dopamine transmission by altering GABA levels. In other words, THC is rewarding and potentially addictive.

Acute effects. In addition to psychoactive effects, cannabis has several other acute effects. Smoking cannabis often results in bloodshot eyes, alterations in blood pressure and heart rate, sleep disturbances, and increases in appetite. However, some tolerance can develop to these effects. Clearly, driving while under the influence is dangerous. Compared to alcohol, the most significant difference between cannabis and driving is that cannabis users will try to compensate for drug effects by driving slower.

Chronic effects. There is evidence of longer-term harms with cannabis use. For example, chronic use can reduce immune system functioning and may lead to infections as a result. Associations between cannabis and psychosis and deficits in cognition and intelligence have also been identified. However, the severity and causal nature of these relationships are still being studied. Finally, there has never been a documented case of someone dying directly from a cannabis overdose.

Addiction potential. Contrary to popular belief, cannabis can be addictive. Now, compared to other drugs, cannabis does have a lower addiction profile. The DSM-5 outlines criteria for Cannabis Use Disorder (CUD). Based on these criteria, upwards of ~10% of regular users would qualify for a CUD. Withdrawal effects are generally uncomfortable but not very serious. Treatment for CUD focuses on psychotherapy, as no effective medications exist to treat CUD at present.

That brings this lesson to a close. In tomorrow’s lesson, we are going to discuss cocaine and amphetamines. See you then!

 

Recommended book

Grass Roots: The Rise and Fall and Rise of Marijuana in America by Emily Dufton

 

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