Whether or not a drug is legal, simplistic slogans, scare tactics and moralizing never help people make responsible choices. Education is the best tool we have, and Washington University has put together the most readable and up to date marijuana web site I have seen.
While being fairly comprehensive, they do not pretend to have all the definitive answers. I will highlight those areas along with more clear-cut ones that were nebulous in my mind thanks to rumors, self-biases and our media’s tendency to put truth through a juicer. In certain cases, I will also provide more detail.
Effects on Memory
Some marijuana users get lost in their thoughts, forget what they are doing, and let immediate objectives slip away. It’s one of the drug’s attractions, allowing people to temporarily escape from drudgery or problems. This in part is due to weed’s effects on short term memory. There are receptors (proteins) which interact with marijuana compounds known as cannabinoids. One receptor- type, CB1, is concentrated in the sea-horse shaped hippocampus, a brain structure involved in memory formation. Long-term impairments may also be possible, but more investigations are needed to see if that concern is real.
More on Cannabinoids
There are close to 100 known cannabinoids,
most of which are not psychoactive. Those that do not act on CB1 receptors but on CB2 receptors are found in the immune system and spleen. The main mind-altering compound acting on CB1 receptors is (−)-trans-Δ9-tetrahydrocannabinol or THC. A single serving in a marijuana edible contains 10 mg of THC. In smokable forms of the drug, the THC concentration of dried leaves, flowering tops and hashish oil ranges from 1 to 20%. Since a joint’s mass is between 0.25 to 1 gram, it translates into a range of 2.5 mg to 200 mg of THC. This is two to seven times stronger than weed from the 1970s, not a factor of 30, as reported in the media.
Cannabidiol (CBD) and its related isomers can make up almost 40% of cannabis resin, and so are the most common group of canniabinoids found in hemp. Although not directly psychoactive, it has other positive effects sought after by medical researchers and patients. Until recently, American marijuana was unfortunately low in cannabidiol, which has a low affinity for both types of receptors but controls the way other cannabinoids interact in the brain and elsewhere in the body. For instance, it may decrease three side effects of THC: anxiety, sleepiness and dependency. This is an example of what researchers Machoulam and Ben-Shabat call the entourage effect. Many marijuana compounds, in individual purified form from the lab, do not act on the human body like they do in a group, as when the plant is smoked or eaten. According to a review of the literature in the British Journal of Pharmacology evidence supports the entourage effect, which is important in medicinal chemistry:
Considered ensemble, the preceding body of information supports the concept that selective breeding of cannabis chemotypes rich in ameliorative phytocannabinoid and terpenoid content offer complementary pharmacological activities that may strengthen and broaden clinical applications and improve the therapeutic index of cannabis extracts containing THC, or other base phytocannabinoids.
Smoking and Driving
A safety margin of 3 to 4 hours is needed to drive after smoking pot and at least 5 to 6 hours if brownies are eaten because the effects of the latter only kick in a couple of hours after ingestion. Under the influence, reflexes can slow down and some “buzzed” drivers do not stay on their lane with optimal ability. Alcohol will accentuate these effects.
Use by adolescents presents higher risks because the brain is in a rapid growth stage, and such early use is more likely to lead to dependence. Cannabis’ short term effects on memory can impact success in school, and if marijuana has any long term effects, a jump start in usage will increase the probability that such effects will materialize. These reasons motivated the setting of the legal age for consumption and purchase of marijuana in Washington state and Colorado at 21, the same for alcohol elsewhere in the country.
Schizophrenics or people genetically predisposed to the condition are at a higher risk of a psychotic episode while under the influence of cannabis, which is a very rare side effect.
THC crosses the placental barrier, and although its effects on the fetus are unknown, pregnant women are advised by doctors to stay clear of it and treat it like tobacco, alcohol or any other psychoactive drug.
Effects on Lungs
Marijuana smoke is less harmful than tobacco. The former does not obstruct airways or cause emphysema. But it’s not entirely innocuous. The connection to pulmonary infections is not clearly established. And there is more tar deposited in the lungs per joint than per tobacco cigarette, so the link to cancer cannot be easily written off. None of the investigations are conclusive so far, and of course any risk will be in proportion to the quantity smoked.