The effects of marijuana have been disputed ever since its ban in 1937. Harry J. Anslinger, the head of the Federal Bureau of Narcotics and Dangerous Drugs (FBNDD) from 1931 to 1962, and his associates like William Randolph Hearst used what has since been termed "yellow journalism" to spread news of marijuana's ill effects. There were claims that marijuana was addictive, caused psychosis and induced violent behavior.
As time progressed, people that wanted to see marijuana remain illegal came up with an ever-increasing list of marijuana's supposed ill effects. This section of my page will follow cannabis through the body from its initial entry into the lungs, to the effects on the lungs themselves, then to the effects on the heart and finally the diverse effects on the brain. Within these sections, I will also address the issues of tolerance and addiction potential, cancer and anti-motivational syndrome.
Smoked marijuana has been shown to be a more effective medicine for a number of ailments, when compared to orally ingested THC capsules. There are a number of methods of smoking marijuana, some of which can help to reduce the inherent perils of inhaling hot vapors containing particulate matter. Common methods include a rolled cigarette or joint, a pipe similar to a tobacco pipe, and various types of water pipes.
Most studies concerning the physiological effects of smoking marijuana have used joints to administer the smoke. This method is commonly used with lower grades of marijuana by casual users, as it is fairly inefficient. Studies have shown that only about 10% to 20% of the THC contained in the original marijuana is converted into main stream smoke that enters the smoker's body, and not all of this is absorbed by the smoker's lungs. (cite Research Findings on Smoking of Abused Substances) Pipes are a more efficient method of smoking, but still allow for less than 45% of the THC to be available to the smoker. (Citation and more information)
So far the most efficient means of smoking has been through a water pipe. These devices have a couple of advantages over conventional pipes. First of all, virtually none of the smoke is lost to the surroundings, or "side-stream smoke." This is achieved by loading the bowl with only as much marijuana as can be inhaled in one breath. The smoker draws all of the smoke into the chamber of the water pipe, combusting all of the marijuana, then "clears" the chamber in one breath. (cite Research Findings on Smoking of Abused Substances p. 45) Another advantage is that the hot smoke is passed through cool water before it reaches the smoker's throat. The advantages to this are twofold. First the smoke is cooled, which makes it easier for the smoker to inhale without coughing and reduces the damage done to the throat. Secondly, as the smoke passes through the water, some of the particulate matter that is suspended in it is filtered into the water. The THC molecule is not water soluble, so very little of it is lost to the water.
A study is currently under way at the Institute for Smoking and Health in New York. Headed by Dr. Hoffman, this study's aim is to determine the harm-reduction potential of smoking marijuana through a water pipe as opposed to other methods. Funded by the Multidisciplinary Association for Psychedelic Studies (MAPS), this study will attempt to determine the most effective type of water pipe, then compare the constituents of the smoke that it provides the smoker with the smoke from a standard unfiltered joint. To determine the most effective water pipe, the researchers will measure the proportions of THC delivered to the amount of tar in the smoke.
This study will also look at the feasibility and
effectiveness of a vaporizer. This device is fundamentally different from
other types of smoking in that it is not actually smoking at all. The
vaporizer heats the marijuana to a point that is hot enough to activate
the THC and release it in the form of steam, but not hot enough to
actually burn the plant material. This form of ingestion holds great
potential for a high THC/tar ratio, but is at this point a tedious
process.
Information about vaporization of cannabis versus smoking it is still
fairly scant, but it is growing.
Early research on cannabis' effects on the brain was limited by the technology of the time and was thus subject to influence by observations of behavior, rather than neuropharmacology. This lack of concrete knowledge about THC's effects allowed cultural biases to maintain fallacy that marijuana acted similarly to heroin. Research done during the past decade, since the discovery of a THC receptor in the brain, has refuted such claims. The congressional Office of Technology Assessment found that recent research findings, especially those done by Dr. Miles Herkenham of the National Institute of Mental Health (NIMH), have proved that marijuana has no effect on the dopamine-related brain systems. (citation)
Dopamine is a neurotransmitter in the brain that is associated with pleasure. The neural systems that are associated with dopamine are known as the "brain reward system." These systems are intimately involved with limbic system, an area of the brain which is associated with the control of emotions and behavior. Highly addictive drugs, such as cocaine, affect these pathways and cause an effective increase in the amount of dopamine in the brain. Cocaine and amphetamines block the reabsorbtion of dopamine, thus prolonging and intensifying the effects. Opiates activate production of dopamine by blocking the inhibitory signal, gamma-aminobutyric acid, which would ordinarily slow or stop dopamine production.
Research on animals and observations of addicts in our population has shown that animals will forsake their own personal good, whether it be refusing food and water or exposing themselves to extreme risk of contracting HIV, in order to stimulate the brain's reward system. Whether or not a drug stimulates the dopamine-associated pathways, is a large determining factor of whether or not the drug will prove to be addictive.
As coined by the Office of Technological Assessment, "The capacity to produce reinforcing effects is essential to any drug with significant abuse potential." (citation) The OTA continued to say, "Animals will not self-administer THC in controlled studies... Cannabinoids generally do not lower the threshold needed to get animals to self-stimulate the brain reward system, as do other drugs of abuse."
Another signal that a drug has a high potential for addiction and abuse is its ability to induce tolerance. Many drugs, such as cocaine and opiates, create a tolerance by wearing out the dopamine receptors in the brain. With a percentage of the receptors being worn out with each exposure, the consumer must progressively increase the dosage to achieve the same effects. This is not the case with THC.
The mammalian brain creates an equilibrium by manipulating the number of active THC receptors to effectively put a ceiling on the drug's effectiveness. The more marijuana a person smokes, fewer THC receptors remain active. If a person rarely smokes, or only does so occasionally, the receptors will stay functioning and the "high" can be achieved with a relatively small dose.
The psychological effects of marijuana are not solely due to THC. While THC is the major psychoactive ingredient that is responsible for the altered sense of reality and euphoric feelings, another constituent of the smoke, cannabinol (CBN), produces only the depressant effects. Tolerance does not develop to this chemical. The paradoxical situation this sets up is this: to maximize the desired effects, a smoker must maintain moderate use. This will keep the THC receptors active, but minimize the proportional amount of CBN ingested. For more information on the specifics of marijuana tolerance, look at Jon Gettman's Marijuana and the Brain, Part II: The Tolerance Factor
The neural toxicity of acute marijuana ingestion was tested by NIDH when they administered a 10 mg/kg dose (a dose that is frequently used in clinical research) of THC to a group of rats. This amount of THC was proportionately more than a very heavy smoker would consume in a week (the approximate equivalent of 670 inhalations from a waterpipe or 100 joints of high-quality {7.5% THC} marijuana for a 165 lb. person). (citation)
The chronic (heavy, regular use) effects of marijuana consumption on the brain are disputed and the evidence available makes it difficult to draw any certain conclusions. R.G. Heath et al found, in their 1979 study of rhesus monkeys, anatomic changes in brain tissue. These changes included widening of the synaptic cleft, clumping of synaptic vesicles and other unspecified changes in morphology of brain cells. These changes were observed 6 months after cessation of 6 months of heavy exposure to marijuana smoke. The report is unclear as to its methods for morphology evaluation and controls that were used. Regardless of slight changes in brain tissue morphology, the behavior and performance levels of the monkeys returned to normal with in 8 months of cessation.(Citation)
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