Marijuana and Medical Marijuana | How Widespread? How Affects Brain, Health.
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Marijuana use in the United States, how widespread? What are the effects of marijuana on the mind? How does marijuana use impact health? What are the uses of medical marijuana? What are the benefits and risks of medical marijuana?

See also:

Adolescent Psychology

The History of Opium

Selecting the Right Drug and Alcohol Rehab

Making a Success of Drug and Alcohol Rehab

Cannabiz: The Explosive Rise of the Medical Marijuana Industry by John Geluardi

Despite the often harsh sentences still meted out for marijuana’s sale and possession, the mind-altering herb’s reputation has come a long way since Reefer Madness days. From once being vilified in the 1938 exploitation film as a catalyst for psychosis and sexual deviance, the drug has more recently been embraced by popular culture, and inspired laws in California and 14 other states regulating the drug as a medicinal aid. After devoting a few cursory chapters to its early history and later demonization by the U.S. government, noted Bay Area reporter Geluardi tracks marijuana’s explosive growth in the last decade both as a recreational drug and an apparent boon for people in ill health.

Some of the players Geluardi focuses on, among cannabis’ increasingly entangled commercial and political interests, include the plant’s growers and sellers, multiplying drug dispensaries, and lobbyists favoring complete legalization. While Geluardi’s workmanlike prose is sometimes overburdened with facts and statistics, the story he tells about cannabis culture’s sudden ascendance from notoriety to mainstream acceptance is both informative and compelling. --Carl Hays - Booklist

Understanding Marijuana: A New Look at the Scientific Evidence by Mitch Earleywine

Marijuana is the world's most popular illicit drug, with hundreds of millions of regular users worldwide. One in three Americans has smoked pot at least once. The Drug Enforcement Agency estimates that Americans smoke five million pounds of marijuana each year. And yet marijuana remains largely misunderstood by both its advocates and its detractors.

To some, marijuana is an insidious "stepping-stone" drug, enticing the inexperienced and paving the way to the inevitable abuse of harder drugs. To others, medical marijuana is an organic means of easing the discomfort or stimulating the appetite of the gravely ill. Others still view marijuana, like alcohol, as a largely harmless indulgence, dangerous only when used immoderately. All sides of the debate have appropriated the scientific evidence on marijuana to satisfy their claims. What then are we to make of these conflicting portrayals of a drug with historical origins dating back to 8,000 B.C.?

Understanding Marijuana examines the biological, psychological, and societal impact of this controversial substance. What are the effects, for mind and body, of long-term use? Are smokers of marijuana more likely than non-users to abuse cocaine and heroine? What effect has the increasing potency of marijuana in recent years had on users and on use? Does our current legal policy toward marijuana make sense? Earleywine separates science from opinion to show how marijuana defies easy dichotomies. Tracing the medical and political debates surrounding marijuana in a balanced, objective fashion, this book will be the definitive primer on our most controversial and widely used illicit substance.

Dying to Get High: Marijuana as Medicine by Wendy Chapkis, Richard Webb

"Chapkis and Webb offer a well-written exposition of the polemics involved in the medical marijuana controversy. . . . Chapkis and Webb have skillfully intertwined abstract concepts with "real life" experiences that exemplify the costs and benefits of the medical marijuana drama."

The Science of Marijuana by Leslie L. Iversen

After alcohol and nicotine, marijuana is the most commonly used "recreational" drug in Western countries, though official positions among different countries vary widely. A debate about the medical applications of marijuana and other cannabis-based preparations has been brewing for years, and pressure to legalise such use continues to increase.

The Science of Marijuana Iversen explains the remarkable advances that have been made in scientific research on cannabis with the discovery of specific receptors and the existence of naturally occurring cannabis-like substances in the brain. Iversen provides an objective and up-to-date assessment of the scientific basis for the medical use of cannabis and what risks this may entail. The recreational use of the drug and how it affects users is described along with some predictions about how attitudes to cannabis may change in the future.

Marijuana Myths Marijuana Facts: A Review Of The Scientific Evidence by Lynn Zimmer (Author), John P. Morgan

A meticulous and concise summaries of the scientific literature make the book a useful primer and a valuable research guide. -- Reason, Jacob Sullum

Legalizing Drugs: Crime Stopper or Social Risk? (USA Today's Debate: Voices and Perspectives) by Margaret J. Goldstein

This book looks at the history of drug laws in the United States, the modern-day War on Drugs, and the medical marijuana movement. It provides the opinions and perspectives of police officers, politicians, and the U.S. "drug czar."

Margaret J. Goldstein was born in Detroit and graduated from the University of Michigan. She is an editor and the author of many Lerner Publishing Group books for young readers and lives in Santa Fe, New Mexico.

Cannabis And Young People: Reviewing the Evidence by -Richard Jenkins

Cannabis is at the centre of ongoing controversial and often confused debate. Opinions on its potential impact on health are sharply divided. Some argue that it poses serious risks to mental health, and that adolescent use may lead to psychotic illness in young adulthood, or that it acts as a gateway to hard drugs such as cocaine or opiates. Conversely, others point to alcohol or tobacco being far more harmful, yet entirely legal.

"Cannabis and Young People" aims to shed light on the current debates by reviewing all the available evidence on a range of issues relating to the use of cannabis among children and adolescents and summarizing the main conclusions in clear, jargon-free language. Areas covered include: patterns of cannabis use; changes in usage; young people's views on cannabis; the potential harmful effects, including mental health problems, educational attainment, antisocial behaviour; the family and social factors that can initiate cannabis use; the progression to regular use; the effects of decriminalization. This book will be an essential read for anyone needing informed, authoritative information about cannabis and its effects.

Written for professionals, and parents, these accessible, evidence-based resources are essential reading for anyone seeking to understand and promote children and young people's mental health. Drawing on the work of FOCUS, a multidisciplinary project based at the Royal College of Psychiatrists' Research Unit, each title in the series brings together practical and policy-level suggestions with up-to-the-minute analysis of research.

Richard Jenkins is a Research Worker at FOCUS, the Royal College of Psychiatrists' Research Unit. He previously worked at the National Collaborating Centre for Mental Health as a systematic reviewer on the NICE guideline for Obsessive Compulsive Disorder. Richard has a first degree in Applied Psychology and an MSc in Health Psychology.


Page updated: November 13, 2015

Marijuana and Medical Marijuana

Marijuana is the most commonly used illicit drug in the United States. It has also been deemed legal for use for some medical conditions, in some states of the U.S.

40% of Americans have used marijuana at least once. Marijuana use is widespread among teens in the United States.

See also,
Marijuana Research, School and Grades, Addiction, Pregnancy (on-site)

What is the Scope of Marijuana Use in the United States?

The most commonly used illicit drug in the United States is marijuana.

There are more than 94 million Americans, which represents approximately 40 percent, who have tried marijuana at least once, according to the 2003 National Survey on Drug Use and Health (NSDUH).23 The ages surveyed included users as young as 12 years of age.

According to The National Institute on Drug Abuse, the use of marijuana is widespread among adolescents and young adults. During the 1990s, the percentage of middle-school students using marijuana increased.24

However, the increase in use of illicit drugs in upper middle school and high school students has leveled off.24 In 2004, though, 16 percent of 8th-grade students had tried marijuana and six-percent were users. (A user is defined as someone who has used the drugs in the 30 days preceding the survey). 16-percent of 10th graders were current users and 20-percent of seniors. About 35-percent of 10th graders had tried marijuana at least once and 46-percent among seniors.

Above information from The National Institute on Drug Abuse (NIDA) U.S. Department of Health and Human Services. Continues after the following section.

Marijuana Use, Especially Heavy Use, and Early-Age-Onset Use Impairs Cognitive Functioning - Harvard-affiliated McLearn Hospital psychiatric clinical study

November 14, 2010 -
Researchers at Harvard-affiliated McLean Hospital have shown that those who start using marijuana at a young age are more impaired on tests of cognitive function than those who start smoking at a later age.

Subjects who started using marijuana before age 16 made twice as many mistakes on tests of executive function, which includes planning, flexibility, abstract thinking and inhibiting inappropriate responses as those who began smoking after age 16.

"They performed significantly worse," said Gruber, director of the Cognitive and Clinical Neuroimaging Core at McLean and assistant professor of Psychiatry at Harvard Medical School.

The early-onset users also smoked three times as much marijuana per week and twice as often compared to the later-onset users, she noted.

Users who started using marijuana before the age of 16, were negatively affected in cognitive functions such as,

  • planning
  • flexibility
  • abstract thinking
  • inhibiting inappropriate responses
  • the early a user begins, the more frequently they smoke later in life

"Habitual marijuana users made repeated errors even when
told that they were wrong."

"Our results provide further evidence that marijuana use has a direct effect on executive function and that both age of onset and magnitude of marijuana use can significantly influence cognitive processing," said Staci A. Gruber, Ph.D., spokesperson of McLean psychiatric.

"Given the prevalence of marijuana use in the United States, these findings underscore the importance of establishing effective strategies to decrease marijuana use, especially in younger populations," she said. "These findings are critical, as adolescence is a time of important brain development, and the adolescent brain is likely more vulnerable to the effects of drugs than the adult brain."

McLean Hospital is the largest psychiatric clinical care, teaching and research facility of Harvard Medical School, an affiliate of Massachusetts General Hospital and a member of Partners HealthCare. For more information about McLean Hospital, visit

Marijuana Use Contributing Factor in Emergency Room Visits and Crime
Marijuana frequently tainted with other drugs

The following information continues from the preceding section, from The National Institute on Drug Abuse (NIDA) - U.S. Department of Health and Human Services unless otherwise referenced.

The Drug Abuse Warning Network (DAWN), is a system for monitoring the health impact of drugs. For the year 2002, it estimated that marijuana was a a contributing factor in over 119,000 emergency room visits in the United States. Approximately 15-percent of the visits were from patients between the ages of 12 and 17. The vast majority, about two-thirds of these, were male.25

Of the total number of persons arrested in 2002, approximately 41-percent of adult males arrested and 27-percent of adult females arrested, tested positive for marijuana, according to the National Institute of Justice's Arrestee Drug Abuse Monitoring (ADAM) Program.

Marijuana sold on the street is frequently combined with other drugs such as PCP, formaldehyde, codeine and crack cocaine, often with the consumer unaware of it.

The NIDA's Community Epidemiology Work Group (CEWG), tracks trends in the nature and patterns of drug use in major cities in the United States. It states that reports on marijuana consistently indicate that the drugs is "frequently combined with other drugs".

Drugs such as crack cocaine, PCP, formaldehyde, and codeine cough syrup, are used or even added to marijuana, at times without the user even being aware of it.21 The risks, then, which are associated with marijuana can often be compounded by the risks of additional drugs, as well.

How does marijuana affect the brain?

Scientists have studied the affect that marijuana and its active ingredient THC, have on the brain. When smoking marijuana, THC passes rapidly from the lungs, through the alveoli, into the bloodstream. The blood then carries the THC throughout the body, including the brain.

The THC connects to specific sites which are referred to as cannabinoid receptors on the nerve cells, or neurons, of the brain, influencing the activity ot these cells. Certain areas of the brain have many cannabinoid receptors, whereas other areas have few or none.

Some of the areas which are affected by THC and that the drug influences are those associated with memory, thought and concentration, pleasure, sensory and time perception, and coordinated movement.27

The Acute Effects of Marijuana Use

While marijuana is usually smoked, at times it is ingested through food or drink. When it is smoked, the effects are immediate and last between one to three hours. It usually starts with a strong 15 to 20 minute "high" followed by a one to three hour mellowing out drug induced state.

If the marijuana is consumed in food or drink, short-term effects begin more slowly, usually within one-half to one hour, but last longer, as long as four hours. Smoking marijuana deposits several times more THC into the blood that does the eating or drinking of marijuana. All of this is true whether one smokes or ingests marijuana for pleasure or for medical reasons. The effects to the body and brain are the same.28

Growing marijuana.

The physical effects, effects to the body, and effects on the mind and brain cells, cognitive impact of the use of marijuana, and the physical and psychological addiction care basically the same, whether marijuana is used for pleasure or for medical reasons (in those states which allow medical marijuana).

Physical effects of marijuana include

  • heart rate
  • bronchial passages
  • and brain
Within a few minutes after inhaling marijuana smoke, the heart beings to beat more rapidly. Normal heart rate is usually about 70 or 80 beats per minute. Marijuana use can increase that rate to 90 to 130 beats (even 140) per minute.15 Bronchial passages relax and become enlarged and the blood vessels expand.

This is why those who have used marijuana frequently have "bloodshot" eyes. The blood vessels in the eyes expand as well. These effects can be even greater when other drugs are combined with marijuana. 29

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.30,31,32

Pleasant Sensations from Marijuana Intoxication,
- Marijuana Use as a Recreational or Illicit Drug

  • pleasant sensations
  • colors and sounds can become intense
  • time can appear to pass more slowly
  • feelings of special and increased perception or insight can occur

Side effects of marijuana use can include,

  • dry mouth
  • hunger or thirst
  • hands may tremble, become cold
  • after a short period of euphoria, sleepiness
  • depression
  • occasionally, intense anxiety
  • paranoia - fear, distrust, panic

Heavy marijuana use impairs a person's ability to form memories, recall events, and can cause the mind to shift attention from one thing to another.8,33 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.11

Marijuana intoxication can result in accidents, because of its effects on the brain and on the body. Approximately six to eleven-percent of fatal accident victims test positive for THC, according to studies. Often, alcohol is used along with marijuana when fatal accidents occur.34, 35, 36

Parts of the brain affected by marijuana,

  • hippocampus
  • cerebellum
  • basal ganglia
Physical bodily (movement) functions which are affected by marijuana

  • balance
  • coordination
  • posture
  • reaction time

Moderate Use of Marijuana Impairs Driving Performance and Results in Deaths

Moderate dosages of marijuana alone, without the use of other drugs or alcohol, impairs driving performance, according to a study conducted by the National Highway Traffic Safety Administration. However, the effects of a low dose of marijuana combined with alcohol were markedly greater than for either drug alone37.

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.

High doses of marijuana can result in,

  • acute toxic psychosis, including hallucinations, delusions, and depersonalization - a loss of the sense of personal identity, or self-recognition.10,15

The specific causes of these acute symptoms remain unknown, however, they appear to occur more frequently when a high dose of cannabis is consumed in food or drink rather than smoked.

Marijuana and Cigarette Smoking

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.38

Respiratory Illness and Cancer from Smoking Marijuana

People who smoke marijuana regularly but who do not smoke tobacco, have more health problems and miss more days of work than those who do not smoke marijuana. Many of the sick days were for respiratory illnesses. The study included 450 individuals.

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.4

Cancer of the respiratory tract and lungs may be promoted by marijuana smoke.

Cancer of the respiratory tract and lungs may also be promoted by marijuana smoke.4 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.17 A statistical analysis of the data suggested that marijuana smoking doubled or tripled the risk of these cancers.

Cancers that may develop through chronic marijuana use

  • Head
  • Neck
  • Lungs and respiratory track
Marijuana has the potential to promote cancer of the lungs and other parts of the respiratory tract because it contains irritants and carcinogens.40 In fact, marijuana smoke contains 50 percent to 70 percent more carcinogenic hydrocarbons than does tobacco smoke.41 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.42

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.16 In other studies, mice exposed to THC or related substances were more likely than unexposed mice to develop bacterial infections and tumors.14,43

THC may impair the immune system's ability to fight off infectious diseases
and cancer.

Greater risk of heart attack in first hour of smoking marijuana
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.44 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, Memory, and the Hippocampus

The brain area known as the hippocampus is effected by the active ingredient in marijuana, THC. The hippocampus is responsible for memory formation. Marijuana's effect on the hippocampus is such that there is damage to the short-term memory.

Laboratory animals which treated with THC displayed the same reduced ability to perform tasks requiring short-term memory as other animals demonstrated after nerve cells in the hippocampus were destroyed.66 Laboratory animals treated with THC had the greatest difficulty with the tasks precisely during the time when the drug was most actively functioning in the brain.

Neurons are normally lost in the hippocampus as people age and this decreases their ability to remember events. Chronic THC exposure may hasten the age-related loss of hippocampus' neurons or brain nerve cells.

In one series of studies, laboratory animals exposed to THC every day for eight months (which represents approximately 30-percent of their lifespan), showed nerve cell loss equivalent to that of unexposed animals twice their age.67, 68, 69

Health Consequences of Marijuana Abuse

  • Acute (present during intoxication)
  • Impairs short-term memory
  • Impairs attention, judgment, and other cognitive functions
  • Impairs coordination and balance
  • Increases heart rate
  • Persistent (lasting longer than intoxication, but may not be permanent)
  • Impairs memory and learning skills
  • Long-term (cumulative, potentially permanent effects of chronic abuse)
  • Can lead to addiction
  • Increases risk of chronic cough, bronchitis, and emphysema
  • Increases risk of cancer of the head, neck, and lungs

The Science of Medical Marijuana

Medical marijuana is a currently hotly debated topic in the United States.
Eli Lilly marketed medical marijuana (THC) before stronger laws took effect in the United States, prior to the 1930s, as illustrated here.

While medical marijuana is a hotly debated topic, it is gradually being legalized (for medical use) in a number of states. THC, the main active ingredient in marijuana, produces effects that are being exploited in medical use. THC is the main ingredient in an oral medication that is currently used to treat nausea in cancer chemotherapy patients. It is also used to stimulate appetite in patients with nutritional-wasting as a result of AIDS.

Other potential uses for medical marijuana are being investigated by scientists.74

Medical marijuana's most widely touted benefit, historically, has been for glaucoma.

Research for Uses of Medical Marijuana
Issues with Medical Marijuana

Some of the research that is currently underway involving medical marijuana are its affect on certain types of pain and spasticity due to multiple schlerosis.

Issues with Medical Marijuana

  • The inconsistency of THC dosage in different marijuana samples is a hindrance to valid trials and to the safe and effective use of the drug.
  • The adverse effects of marijuana smoke on the respiratory system will offset the helpfulness of smoked marijuana for some patients.4,5,6
  • Other chemicals present in marijuana, additional to THC, may contribute to health and mental difficulties with patients who have previous medical conditions.

Potential for Proliferation of Marijuana Use Through Legalization of the Drug

While medical marijuana may be of some help and may have limited medical value in certain situations, its use can, at the same time, result in other, sometimes, more serious health and mental health issues and problems.

Moreover, the smoker's high is present for those who use marijuana medicinally, as well as for those who use marijuana recreationally. Memory, cognitive and performance impairment resulting from regular marijuana use may the same for those who use the drug medicinally as those who use it illicitly.

Another issue regarding the legalization of marijuana for medical use is that of its proliferation into illicit channels, that is, in the streets and possibly into the hands of teens and children.

Nederland, Colorado, a hippie town, one medical marijuana depot
per every 175 residents

As one example, in the little town of Nederland, Colorado, an old hippie town where "smoking pot" is as common as drinking herbal tea, the 1,400 residents share the distinction of having the largest per-capita medical marijuana depots in the United States, with a total of eight. That means that there is one medical marijuana depot for approximately every 175 residents.

In this county, one in 20 residents qualify for medical marijuana. Ron Hyman, the state registrar of vital statistics and director of the Colorado Department of Public Health and Environment's medical marijuana program, as quoted in the New York Times asked, "Who would think there would be such severe pain among young men in Colorado?" [77]

Ritalin is an example of a prescribed drug, which also finds its way into illegal channels, and as a result is the 4th most abused drug. It is bought and sold on the street, although the primary first-source of Ritalin is by means of prescriptions.

If a teen using Ritalin for ADHD can make a few dollars a pill, why not skip a dose and sell a few for extra money? Marijuana has even wider appeal for its use as a recreational and potentially physically and performance impairing drug, which is abused by teens and even be pre-teens in the inner city. Teachers who have had students who smoke marijuana regularly, know how marijuana use by teens can affect their behavior and make it more challenging to deal with individual students. and slows down their ability to perform academically or cognitively.

See: Marijuana Mental Effects (on-site)

Moreover, both physical and psychological addiction to marijuana are issues, using marijuana to relieve stress as a daily habit can make marijuana a difficult drug to quit, even for those who desire to do so. The addiction, in the case of marijuana, can be both physical as well as psychological.

Both physical craving and psychological addiction can result
from frequent marijuana use

Therefore, while limited value may be realized through the use of medical marijuana, psychologically, the proliferation and legitimization of marijuana use as a lifestyle is counterproductive to individuals and to society as a whole.

References for Marijuana and Medical Marijuana (on site webpage)

Glossary for Marijuana and Medical Marijuana

Addiction: A chronic, relapsing disease characterized by compulsive drug-seeking and abuse and by long-lasting chemical changes in the brain.

Cannabinoids: Chemicals that help control mental and physical processes when produced naturally by the body and that produce intoxication and other effects when absorbed from marijuana.

Carcinogen: Any substance that causes cancer.

Dopamine: A brain chemical, classified as a neurotransmitter, found in regions of the brain that regulate movement, emotion, motivation, and pleasure.

Hippocampus: An area of the brain crucial for learning and memory.

Hydrocarbon: Any chemical compound containing only hydrogen and carbon.

Neurons: Nerve cells in the brain. Psychoactive: Having a specific effect on the mind.

THC: Delta-9-tetrahydrocannabinol; the main active ingredient in marijuana, which acts on the brain to produce its effects. Withdrawal: Symptoms that occur after use of a drug is reduced or stopped.

Source: Adapted from The National Institute on Drug Abuse (NIDA)
U.S. Department of Health and Human Services.

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