Marijuana Information

What is marijuana?

weed plantMarijuana is a green or gray mixture of dried, shredded flowers and leaves of the hemp plant Cannabis sativa. There are over 200 slang terms for marijuana including “pot,” “herb,” “weed,” “boom,” “Mary Jane,” “gangster,” and “chronic.” It is usually smoked as a cigarette (called a joint or a nail) or in a pipe or bong. In recent years, it has appeared in blunts. These are cigars that have been emptied of tobacco and re-filled with marijuana, often in combination with another drug, such as crack. Some users also mix marijuana into foods or use it to brew tea.

The main active chemical in marijuana is THC (delta-9-tetrahydrocannabinol). In 1988, it was discovered that the membranes of certain nerve cells contain protein receptors that bind THC. Once securely in place, THC kicks off a series of cellular reactions that ultimately lead to the high that users experience when they smoke marijuana. The short-term effects of marijuana use include problems with memory and learning; distorted perception; difficulty in thinking and problem solving; loss of coordination; and increased heart rate, anxiety, and panic attacks.

bag of weedScientists have found that whether an individual has positive or negative sensations after smoking marijuana can be influenced by heredity. A recent study demonstrated that identical male twins were more likely than nonidentical male twins to report similar responses to marijuana use, indicating a genetic basis for their sensations. Identical twins share all of their genes, and fraternal twins share about half. Environmental factors such as the availability of marijuana, expectations about how the drug would affect them, the influence of friends and social contacts, and other factors that would be different even for identical twins also were found to have an important effect; however, it also was discovered that the twins’ shared or family environment before age 18 had no detectable influence on their response to marijuana.

How is marijuana used?

smoking weedCannabis products are usually smoked. Their effects are felt within minutes, reach their peak in 10 to 30 minutes, and may linger for two or three hours. The effects experienced often depend upon the experience and expectations of the individual user as well as the activity of the drug itself. Low doses tend to induce a sense of well-being and a dreamy state of relaxation, which may be accompanied by a more vivid sense of sight, smell, taste, and hearing as well as by subtle alterations in thought formation and expression. This state of intoxication may not be noticeable to an observer. However, driving, occupational or household accidents may result from a distortion of time and space relationships and impaired coordination. Stronger doses intensify reactions. The individual may experience shifting sensory imagery, rapidly fluctuating emotions, a flight of fragmentary thoughts with disturbed associations, an altered sense of self-identity, impaired memory, and a dulling of attention despite an illusion of heightened insight. High doses may result in image distortion, a loss of personal identity, and fantasies and hallucinations.

Health hazards

Marijuana contains known toxins and cancer-causing chemicals which are stored in fat cells for as long as several months. Marijuana users experience the same health problems as tobacco smokers, such as bronchitis, emphysema and bronchial asthma. Some of the effects of marijuana use also include: an increased heart rate, dryness of the mouth, reddening if the eyes, impaired motor skills and concentration, and frequent hunger and an increased desire for sweets. Extended use increases risk to the lungs and reproductive system, as well as suppression of the immune system. Occasionally hallucinations, fantasies and paranoia are reported.

Effects of Marijuana on the Brain

Researchers have found that THC changes the way in which sensory information gets into and is acted on by the hippocampus. This is a component of the brain’s limbic system that is crucial for learning, memory, and the integration of sensory experiences with emotions and motivations. Investigations have shown that neurons in the information processing system of the hippocampus and the activity of the nerve fibers are suppressed by THC. In addition, researchers have discovered that learned behaviors, which depend on the hippocampus, also deteriorate.

Recent research findings also indicate that long-term use of marijuana produces changes in the brain similar to those seen after long-term use of other major drugs of abuse.

Effects on the Lungs

Someone who smokes marijuana regularly may have many of the same respiratory problems that tobacco smokers have. These individuals may have daily cough and phlegm, symptoms of chronic bronchitis, and more frequent chest colds. Continuing to smoke marijuana can lead to abnormal functioning of lung tissue injured or destroyed by marijuana smoke.

Regardless of the THC content, the amount of tar inhaled by marijuana smokers and the level of carbon monoxide absorbed are three to five times greater than among tobacco smokers. This may be due to the marijuana users inhaling more deeply and holding the smoke in the lungs.

Effects on Heart Rate and Blood Pressure

Recent findings indicate that smoking marijuana while shooting up cocaine has the potential to cause severe increases in heart rate and blood pressure. In one study, experienced marijuana and cocaine users were given marijuana alone, cocaine alone, and then a combination of both. Each drug alone produced cardiovascular effects; when they were combined, the effects were greater and lasted longer. The heart rate of the subjects in the study increased 29 beats per minute with marijuana alone and 32 beats per minute with cocaine alone. When the drugs were given together, the heart rate increased by 49 beats per minute, and the increased rate persisted for a longer time. The drugs were given with the subjects sitting quietly. In normal circumstances, an individual may smoke marijuana and inject cocaine and then do something physically stressful that may significantly increase risks of overload on the cardiovascular system.

Effects of Heavy Marijuana Use on Learning and Social Behavior

A study of college students has shown that critical skills related to attention, memory, and learning are impaired among people who use marijuana heavily, even after discontinuing its use for at least 24 hours. Researchers compared 65 “heavy users,” who had smoked marijuana a median of 29 of the past 30 days, and 64 “light users,” who had smoked a median of 1 of the past 30 days. After a closely monitored 19- to 24-hour period of abstinence from marijuana and other illicit drugs and alcohol, the undergraduates were given several standard tests measuring aspects of attention, memory, and learning. Compared to the light users, heavy marijuana users made more errors and had more difficulty sustaining attention, shifting attention to meet the demands of changes in the environment, and in registering, processing, and using information. The findings suggest that the greater impairment among heavy users is likely due to an alteration of brain activity produced by marijuana.

Longitudinal research on marijuana use among young people below college age indicates those who used have lower achievement than the non-users, more acceptance of deviant behavior, more delinquent behavior and aggression, greater rebelliousness, poorer relationships with parents, and more associations with delinquent and drug-using friends.

Research also shows more anger and more regressive behavior (thumb sucking, temper tantrums) in toddlers whose parents use marijuana than among the toddlers of non-using parents.

Effects on Pregnancy

Any drug of abuse can affect a mother’s health during pregnancy, and this is a time when she should take special care of herself. Drugs of abuse may interfere with proper nutrition and rest, which can affect good functioning of the immune system. Some studies have found that babies born to mothers who used marijuana during pregnancy were smaller than those born to mothers who did not use the drug. In general, smaller babies are more likely to develop health problems.

A nursing mother who uses marijuana passes some of the THC to the baby in her breast milk. Research indicates that the use of marijuana by a mother during the first month of breast-feeding can impair the infant’s motor development (control of muscle movement).

Addictive Potential

A drug is addicting if it causes compulsive, often uncontrollable drug craving, seeking, and use, even in the face of negative health and social consequences. Marijuana meets this criterion. More than 120,000 people seek treatment per year for their primary marijuana addiction. In addition, animal studies suggest marijuana causes physical dependence, and some people report withdrawal symptoms.

Extent of Use

National Survey on Drug Use and Health
Based on SAMHSA’s 2003 National Survey on Drug Use and Health, 3.1 million persons aged 12 or older used marijuana daily, that is, on 300 or more days in the past year. Between 2002 and 2003, the number of 12 to 17 year olds reporting daily use of marijuana decreased from 358,000 to 282,000; while there were no changes in the number of daily marijuana users among 18-25 year olds or adults age 26 or older.

An estimated 39.2% of daily marijuana users were dependent on or abused marijuana compared with 13.5% of less-than-daily marijuana users.

Daily marijuana users (63.3%) were more likely than less-than-daily marijuana users (38.8%) or non marijuana users (4.6%) to use another illicit drug. Daily marijuana users also were more likely to be current cigarette smokers and heavy drinkers.

More than half of daily marijuana users (53.3%) reported dependence on or abuse of alcohol or an an illicit drug compared with those who were less-than-daily users (36.5%) and nonusers (5.6%).

The percentage of youths aged 12 to 17 who had ever used marijuana declined slightly from 2001 to 2002 (21.9 to 20.6 percent). Among young adults aged 18 to 25, the rate increased slightly from 53.0 percent in 2001 to 53.8 percent in 2002 (Figure 5.1).

In 1965 and 1966, only 1.8 percent of youths had ever used marijuana. Beginning in 1967, use increased until it reached a peak at 19.6 percent in 1979. A period of decline followed until 1991, when the rate was 11.5 percent, after which the trend reversed, reaching a peak at 21.9 percent in 2001.

The percentage of young adults aged 18 to 25 who had ever used marijuana was 5.1 percent in 1965, but increased steadily to 54.4 percent in 1982. Although the rate for young adults declined somewhat from 1982 to 1993, it did not drop below 43 percent and actually increased to 53.8 percent by 2002.

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