According to the United Nations, marijuana is the world’s most commonly used illegal drug. In 2004, the United Nations also reported that there were more than 162 million users worldwide (4% of the population) and 22.5 million people who use it on a daily basis (.6 % of the population). There are 16.7 million active users (admitted to smoking cannabis in the past month) in the United States alone, according to the 2009 National Survey on Drug Use.
Marijuana comes from the hemp plant commonly known as cannabis sativa; it can be further classified into 4 strains (sativa, indica, ruderalis, and afghanica) but the two most common forms are cannabis sativa and cannabis indica. Of the two, cannabis sativa is the most common and has the recognizable leaf seen here. Indica is somewhat less prevalent but considerably more potent. Cannabis has more than 400 chemicals, 60 of which fit into a category called cannabinoids.
Cannabinoids are chemical compounds that are found within cannabis but also found within the nervous and immune systems of animals, including humans. They comprise the active ingredients in marijuana that produce the altered states of consciousness, otherwise known as the ‘high’. The most potent cannabinoid, and the one familiar to most people, is called THC which is short for “delta-9 tetrahydrocannabinol”. The THC levels can vary greatly among different strains and even different batches depending on the growing conditions; some strains of marijuana have gone through a careful selection process with expert growing techniques and can produce plants with up to 29% THC. THC is a powerful substance compared to other psychoactive drugs. For example, an IV (intravenous) dose of only 1 milligram can produce serious mental and psychological effects. Cannabis is usually smoked like a cigarette (“joint”), but it can also be baked into brownies or cookies, made into butter or brewed like tea.
The first written account of cannabis cultivation was found in Chinese records that dated from 28 BC. The Chinese have been growing marijuana for over 2000 years, yet it is believed to have originated in India so its history presumably goes back even further. There are reports of an alleged 3,000 year old Egyptian mummy that has been found with traces of THC.
Effects on the Brain
Marijuana affects the central nervous system by attaching to the brain’s neurons (cells that process information) and interfering with normal communication between the neurons. Once marijuana is inhaled or consumed, the active THC compound is carried to the brain by the bloodstream. In the brain, it binds to the cannabinoid receptors of the neurons and causes them to change their actions. An abundance of cannabinoid receptors are found in those regions of the brain which control memory, thought, sensations of pleasure, perception and concentration. These cannabinoid receptors weren’t discovered until 1990, and it wasn’t until 1992 that they discovered why we even had these receptors in our brains.
It turns out that we have a substance called anandamide which is the equivalent of your brain’s own THC (just like endorphins are your brain’s equivalent to morphine). By altering the actions of the neurons it negatively affects memory, concentration, cognitive functioning as well as creating distorted sensory and time perceptions. THC also results in changes in the levels of certain neurotransmitters (chemical messengers that carry signals between the neurons) -particularly dopamine and norepinephrine- thereby stimulating regions of the brain which produce sensations of pleasure or euphoria. That explains why individuals using marijuana feel a sense of elation.
Cannabinoid receptor sites are found in many areas of the brain although some areas have an abundance of them while others have few. The regions of the brain where cannabinoid receptors are most prevalently located are the hippocampus, the basal ganglia and the cerebellum. The hippocampus is associated with memory and learning; the cerebellum is associated with movement coordination; and the basal cell ganglia are associated with movement control. These receptors are also found in the cerebral cortex which is associated with higher cognitive functions and in the nucleus accumbens which is regarded as the reward center of the brain. They are found in other areas of the brain as well but less abundantly. When THC activates the cannabinoid receptors, it interferes with the normal functioning of these brain regions.
The areas regulating motor control and memory are where the effects of the cannabis are most notable. Depending on the dose, cannabinoids inhibit the normal transmission of neural signals through the basal ganglia and cerebellum. At lower doses, cannabinoids seem to fuel locomotion while larger doses inhibit locomotion, usually manifested by a lack of steadiness in motor tasks that require attention. Other brain regions (like the cerebellum, cortex, etc.) are also known to be involved in the control of movement and they also contain cannabinoid receptors, suggesting that they may be involved as well.
Another interesting neurological result of cannabis is the effect on the brain’s alpha waves. Studies have shown that people who smoked marijuana had EEG (electroencephalography) results that showed somewhat more continual alpha waves of lower frequency than normal. Alpha waves are a sign of decreased motor activity.
Is Marijuana Medicine?
Despite heated debate over the issue of legalizing marijuana, five European countries, Canada and 18 U.S. states (17 plus the District of Columbia) have legalized cannabis for medicinal purposes. Scientific studies have concluded that the cannabis plant does contain active ingredients that can have a therapeutic effect on relieving pain, controlling nausea, stimulating appetite and decreasing ocular pressure. It has been shown to be beneficial in the treatment of AIDS, cancer, multiple sclerosis, chronic pain and glaucoma. The effects of cannabis sativa strains are well known for their cerebral high and therefore used as daytime medical cannabis, while the strains of cannabis indica are better known for their sedative effects and are preferred as night time medical cannabis.
THC and cannabidiol (another cannabinoid) are also ‘neuroprotective antioxidants’. Research in rats has indicated that THC prevented oxidative damage as well as, or better than, other antioxidants in a chemical system and neuronal cultures. Cannabidiol proved to be more protective than either vitamin E or vitamin C. This research has not been replicated with humans yet to see if THC and cannabidiol are antioxidants for people as well.
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