Marijuana
Marijuana - often called grass, reefer, weed, herb, mary jane, or mj-is a greenish-gray mixture of the dried, shredded leaves, stems, seeds, and flowers of Cannabis sativa, the hemp plant. Most users smoke marijuana in hand-rolled cigarettes called joints. Marijuana also is used to brew tea and is sometimes mixed into foods. There are more than 200 slang terms for marijuana, including “pot,” “herb,” “weed,” “Mary Jane,” “grass,” “tea,” and “ganja.”
It is usually chopped and/or shredded and rolled into a cigarette, or “joint,” or placed in a pipe (sometimes called a “bong") and smoked. An alternative method of using marijuana involves adding it to foods and eating it, such as baking it into brownies. It can also be brewed as a tea. Marijuana has appeared in the form of “blunts"-cigarettes emptied of their tobacco content and filled with a combination of marijuana and another drug such as crack cocaine.
The major active chemical in marijuana is delta-9-tetrahydrocannabinol (THC), which causes the mind-altering effects of marijuana intoxication. The amount of THC (which is also the psychoactive ingredient in hashish) determines the potency and, therefore, the effects of marijuana. Between 1980 and 1997, the amount of THC in marijuana available in the United States rose dramatically.
BRAIN EFFECTS OF MARIJUANA
Scientists have learned a great deal about how THC acts in the brain to produce its many effects. When someone smokes marijuana, THC rapidly passes from the lungs into the bloodstream, which carries the chemical to organs throughout the body, including the brain. In the brain, THC connects to specific sites called cannabinoid receptors on nerve cells and thereby influences the activity of those cells. Some brain areas have many cannabinoid receptors; others have few or none. Many cannabinoid receptors are found in the parts of the brain that influence pleasure, memory, thought, concentration, sensory and time perception, and coordinated movement.
ACUTE EFFECTS OF MARIJUANA USE
When marijuana is smoked, its effects begin immediately after the drug enters the brain and last from 1 to 3 hours. If marijuana is consumed in food or drink, the short-term effects begin more slowly, usually in 1/2 to 1 hour, and last longer, for as long as 4 hours. Smoking marijuana deposits several times more THC into the blood than does eating or drinking the drug.
Within a few minutes after inhaling marijuana smoke, an individual’s heart begins beating more rapidly, the bronchialpassages relax and become enlarged, and blood vessels in the eyes expand, making the eyes look red. The heart rate, normally 70 to 80 beats per minute, may increase by 20 to 50 beats per minute or, in some cases, even double. This effect can be greater if other drugs are taken with marijuana.
As THC enters the brain, it causes a user to feel euphoric - or “high” - by acting in the brain’s reward system, areas of the brain that respond to stimuli such as food and drink as well as most drugs of abuse. THC activates the reward system in the same way that nearly all drugs of abuse do, by stimulating brain cells to release the chemical dopamine.
A marijuana user may experience pleasant sensations, colors and sounds may seem more intense, and time appears to pass very slowly. The user’s mouth feels dry, and he or she may suddenly become very hungry and thirsty. His or her hands may tremble and grow cold. The euphoria passes after awhile, and then the user may feel sleepy or depressed. Occasionally, marijuana use produces anxiety, fear, distrust, or panic.
Heavy marijuana use impairs a person’s ability to form memories, recall events, and shift attention from one thing to another. THC also disrupts coordination and balance by binding to receptors in the cerebellum and basal ganglia, parts of the brain that regulate balance, posture, coordination of movement, and reaction time. Through its effects on the brain and body, marijuana intoxication can cause accidents. Studies show that approximately 6 to 11 percent of fatal accident victims test positive for THC. In many of these cases, alcohol is detected as well.
In a study conducted by the National Highway Traffic Safety Administration, a moderate dose of marijuana alone was shown to impair driving performance; however, the effects of even a low dose of marijuana combined with alcohol were markedly greater than for either drug alone. Driving indices measured included reaction time, visual search frequency (driver checking side streets), and the ability to perceive and/or respond to changes in the relative velocity of other vehicles.
Marijuana users who have taken high doses of the drug may experience acute toxic psychosis, which includes hallucinations, delusions, and depersonalization- a loss of the sense of personal identity, or self-recognition. Although the specific causes of these symptoms remain unknown, they appear to occur more frequently when a high dose of cannabis is consumed in food or drink rather than smoked.
PHYSICAL HEALTH DANGERS OF MARIJUANA USE
Marijuana use has been shown to increase users’ difficulty in trying to quit smoking tobacco.13 This was reported in a study comparing smoking cessation in adults who smoked both marijuana and tobacco with those who smoked only tobacco. The relationship between marijuana use and continued smoking was particularly strong in those who smoked marijuana daily at the time of the initial interview, 13 years prior to the followup interview.
A study of 450 individuals found that people who smoke marijuana frequently but do not smoke tobacco have more health problems and miss more days of work than nonsmokers do. Many of the extra sick days used by the marijuana smokers in the study were for respiratory illnesses.
Even infrequent marijuana use can cause burning and stinging of the mouth and throat, often accompanied by a heavy cough. Someone who smokes marijuana regularly may have many of the same respiratory problems that tobacco smokers do, such as daily cough and phlegm production, more frequent acute chest illnesses, a heightened risk of lung infections, and a greater tendency toward obstructed airways.
Marijuana smoke is known to contain even larger amounts of carcinogens than tobacco smoke. Cancer of the respiratory tract and lungs may also be promoted by marijuana smoke. A study comparing 173 cancer patients and 176 healthy individuals produced strong evidence that smoking marijuana increases the likelihood of developing cancer of the head or neck, and that the more marijuana smoked, the greater the increase. A statistical analysis of the data suggested that marijuana smoking doubled or tripled the risk of these cancers.
Marijuana has the potential to promote cancer of the lungs and other parts of the respiratory tract because it contains irritants and carcinogens. In fact, marijuana smoke contains 50 percent to 70 percent more carcinogenic hydrocarbons than does tobacco smoke. It also produces high levels of an enzyme that converts certain hydrocarbons into their carcinogenic form, levels that may accelerate the changes that ultimately produce malignant cells. Marijuana users usually inhale more deeply and hold their breath longer than tobacco smokers do, which increases the lungs’ exposure to carcinogenic smoke. These facts suggest that, puff for puff, smoking marijuana may increase the risk of cancer more than smoking tobacco does.
Some adverse health effects caused by marijuana may occur because THC impairs the immune system’s ability to fight off infectious diseases and cancer. In laboratory experiments that exposed animal and human cells to THC or other marijuana ingredients, the normal disease-preventing reactions of many of the key types of immune cells were inhibited. In other studies, mice exposed to THC or related substances were more likely than unexposed mice to develop bacterial infections and tumors.
One study has indicated that a person’s risk of heart attack during the first hour after smoking marijuana is four times his or her usual risk. The researchers suggest that a heart attack might occur, in part, because marijuana raises blood pressure and heart rate and reduces the oxygen-carrying capacity of blood.
Marijuana use has been shown to increase users’ difficulty in trying to quit smoking tobacco. This was reported in a study comparing smoking cessation in adults who smoked both marijuana and tobacco with those who smoked only tobacco. The relationship between marijuana use and continued smoking was particularly strong in those who smoked marijuana daily at the time of the initial interview, 13 years prior to the followup interview.
MARIJUANA USE AFFECT ON SCHOOL, WORK and SOCIAL LIFE
Students who smoke marijuana get lower grades and are less likely to graduate from high school, compared with their nonsmoking peers
Workers who smoke marijuana are more likely than their coworkers to have problems on the job. Several studies have associated workers’ marijuana smoking with increased absences, tardiness, accidents, workers’ compensation claims, and job turnover. A study among postal workers found that employees who tested positive for marijuana on a pre-employment urine drug test had 55 percent more industrial accidents, 85 percent more injuries, and a 75-percent increase in absenteeism compared with those who tested negative for marijuana use.
Depression, anxiety, and personality disturbances are all associated with marijuana use. Research clearly demonstrates that marijuana use has the potential to cause problems in daily life or make a person’s existing problems worse. Because marijuana compromises the ability to learn and remember information, the more a person uses marijuana the more he or she is likely to fall behind in accumulating intellectual, job, or social skills. In one study of cognition, adults were matched on the basis of their performance in the 4th grade on the Iowa Test of Basic Skills. They were evaluated on a number of cognitive measures including the 12th-grade version of the Iowa Test. Those who were heavy marijuana smokers scored significantly lower on mathematical skills and verbal expression than nonsmokers.
Moreover, research has shown that marijuana’s adverse impact on memory and learning can last for days or weeks after the acute effects of the drug wear off. For example, a study of 129 college students found that among heavy users of marijuana-those who smoked the drug at least 27 of the preceding 30 days-critical skills related to attention, memory, and learning were significantly impaired, even after they had not used the drug for at least 24 hours.10 The heavy marijuana users in the study had more trouble sustaining and shifting their attention and in registering, organizing, and using information than did the study participants who had used marijuana no more than 3 of the previous 30 days. As a result, someone who smokes marijuana once daily may be functioning at a reduced intellectual level all of the time. More recently, the same researchers showed that a group of long-term heavy marijuana users’ ability to recall words from a list was impaired 1 week following cessation of marijuana use, but returned to normal by 4 weeks.16 An implication of this finding is that even after long-term heavy marijuana use, if an individual quits marijuana use, some cognitive abilities may be recovered.
Another study produced additional evidence that marijuana’s effects on the brain can cause cumulative deterioration of critical life skills in the long run. esearchers gave students a battery of tests measuring problem-solving and emotional skills in 8th grade and again in 12th grade. The results showed that the students who were already drinking alcohol plus smoking marijuana in 8th grade started off slightly behind their peers, but that the distance separating these two groups grew significantly by their senior year in high school. The analysis linked marijuana use, independently of alcohol use, to reduced capacity for selfreinforcement, a group of psychological skills that enable individuals to maintain confidence and persevere in the pursuit of goals.
Marijuana users themselves report poor outcomes on a variety of measures of life satisfaction and achievement. A recent study compared current and former longterm heavy users of marijuana with a control group who reported smoking cannabis at least once in their lives, but not more than 50 times. Despite similar education and incomes in their families of origin, significant differences were found in educational attainment and income between heavy users and the control group: fewer of the cannabis users completed college and more had household incomes of less than $30,000. When asked how marijuana affected their cognitive abilities, career achievements, social lives, and physical and mental health, the overwhelming majority of heavy cannabis users reported the drug’s deleterious effect on all of these measures.
MARIJUANA USE DURING PREGNANCY
Research has shown that some babies born to women who used marijuana during their pregnancies display altered responses to visual stimuli, increased tremulousness, and a high-pitched cry, which may indicate problems with neurological development. During the preschool years, marijuanaexposed children have been observed to perform tasks involving sustained attention and memory more poorly than nonexposed children do. In the school years, these children are more likely to exhibit deficits in problem-solving skills, memory, and the ability to remain attentive.
IS MARIJUANA USE ADDICTIVE?
Long-term marijuana use can lead to addiction for some people; that is, they use the drug compulsively even though it often interferes with family, school, work, and recreational activities. According to the 2003 National Survey on Drug Use and Health (NSDUH), an estimated 21.6 million Americans aged 12 or older were classified with substance dependence or abuse (9.1 percent of the total population). Of the estimated 6.9 million Americans classified with dependence on or abuse of illicit drugs, 4.2 million were dependent on or abused marijuana. In 2002, 15 percent of people entering drug abuse treatment programs reported that marijuana was their primary drug of abuse.
Along with craving, withdrawal symptoms can make it hard for long-term marijuana smokers to stop using the drug.15 People trying to quit report irritability, difficulty sleeping, and anxiety. They also display increased aggression on psychological tests, peaking approximately 1 week after they last used the drug.
In addition to its addictive liability, research indicates that early exposure to marijuana can increase the likelihood of a lifetime of subsequent drug problems. A recent study of over 300 fraternal and identical twin pairs, who differed on whether or not they used marijuana before the age of 17, found that those who had used marijuana early had elevated rates of other drug use and drug problems later on, compared with their twins, who did not use marijuana before age 17. This study re-emphasizes the importance of primary prevention by showing that early drug initiation is associated with increased risk of later drug problems, and it provides more evidence for why preventing marijuana experimentation during adolescence could have an impact on preventing addiction.
Source: An extract from NIDA Reaserch Report Series
