NIDA InfoFacts: Marijuana (THC)
Marijuana is the most commonly abused illicit drug in the United States.
A dry, shredded green/brown mix of flowers, stems, seeds, and leaves of the
hemp plant Cannabis sativa, it usually is smoked as a cigarette (joint,
nail), or in a pipe (bong). It also is smoked in blunts, which are cigars
that have been emptied of tobacco and refilled with marijuana, often in
combination with another drug. It might also be mixed in food or brewed as a
tea. As a more concentrated, resinous form it is called hashish and, as a
sticky black liquid, hash oil. Marijuana smoke has a pungent and
distinctive, usually sweet-and-sour odor. There are countless street terms
for marijuana including pot, herb, weed, grass, widow, ganja, and hash, as
well as terms derived from trademarked varieties of cannabis, such as Bubble
Gum, Northern Lights, Fruity Juice, Afghani #1, and a number of Skunk
varieties.
The main active chemical in marijuana is THC (delta-9-tetrahydrocannabinol).
The membranes of certain nerve cells in the brain contain protein receptors
that bind to 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.
Extent of Use
In 2004, 14.6 million Americans age 12 and older used marijuana at least once
in the month prior to being surveyed. About 6,000 people a day in 2004 used marijuana for the first time—2.1 million Americans. Of these, 63.8 percent were
under age 181. In the last half of 2003,
marijuana was the third most commonly abused drug mentioned in drug-related
hospital emergency department (ED) visits in the continental United States, at
12.6 percent, following cocaine (20 percent) and alcohol (48.7 percent)2.
Prevalence of lifetime,* annual, and use within the last 30 days for marijuana
remained stable among 10th- and 12th-graders surveyed between 2003 and 2004.
However, 8th-graders reported a significant decline in 30-day use and a
significant increase in perceived harmfulness of smoking marijuana once or twice
and regularly3. Trends in disapproval of using
marijuana once or twice and occasionally rose among 8th-graders as well, and
10th-graders reported an increase in disapproval of occasional and regular use
for the same period3.
Percentage of 8th-Graders Who Have Used Marijuana:
Monitoring the Future Study, 2005
|
|
Percentage of 10th-Graders Who Have Used Marijuana:
Monitoring the Future Study, 2005
|
|
Percentage of 12th-Graders Who Have Used Marijuana
Monitoring the Future Study, 2005
|
|
| * "Lifetime" refers to use at least once during a respondent’s lifetime. "Annual" refers to use at least once during the year preceding an individual's response to the survey. "30-day" refers to use at least once during the 30 days preceding an individual’s response to the survey. |
Effects on the Brain
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 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 movement4.
The short-term effects of marijuana can include problems with memory and
learning; distorted perception; difficulty in thinking and problem solving; loss
of coordination; and increased heart rate. Research findings for long-term
marijuana abuse indicate some changes in the brain similar to those seen after
long-term abuse of other major drugs. For example, cannabinoid (THC or synthetic
forms of THC) withdrawal in chronically exposed animals leads to an increase in
the activation of the stress-response system5
and changes in the activity of nerve cells containing dopamine6.
Dopamine neurons are involved in the regulation of motivation and reward, and
are directly or indirectly affected by all drugs of abuse.
Effects on the Heart
One study has indicated that an abuser's risk of heart attack more than quadruples in the first hour after smoking marijuana7. The researchers suggest that such an effect might occur from marijuana's effects on blood pressure and heart rate and reduced oxygen-carrying capacity of blood.
Effects on the Lungs
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 nonsmokers8. Many of the extra sick days
among the marijuana smokers in the study were for respiratory illnesses.
Even infrequent abuse 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 illness, a
heightened risk of lung infections, and a greater tendency to obstructed airways9.
Smoking marijuana possibly increases the likelihood of developing cancer of the head or neck. A study comparing 173 cancer patients and 176 healthy individuals
produced evidence that marijuana smoking doubled or tripled the risk of these
cancers10.
Marijuana abuse also has the potential to promote cancer of the lungs and other
parts of the respiratory tract because it contains irritants and carcinogens9,11.
In fact, marijuana smoke contains 50 to 70 percent more carcinogenic
hydrocarbons than does tobacco smoke12. It also
induces high levels of an enzyme that converts certain hydrocarbons into their
carcinogenic form—levels that may accelerate the changes that ultimately produce
malignant cells13. 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 be more harmful to the lungs than smoking
tobacco.
Products we offer for Peace of Mind...
5 Panel Rapid
Drug Test:
Screening Solutions offers parents a effective means of testing
your child for the presence of illegal drugs. Our instant drug test screens for Cocaine, Methamphetamines,
Marijuana, Opiates and Phencyclidine. Get the answers you need to
make better decisions by home testing.
Other Health Effects
Some of marijuana's adverse health effects may occur because THC impairs the immune system's ability to fight disease. 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 inhibited14. In other studies, mice exposed to THC or related substances were more likely than unexposed mice to develop bacterial infections and tumors15,16.
Effects of Heavy Marijuana Use on Learning and Social Behavior
Research clearly demonstrates that marijuana has the potential to cause
problems in daily life or make a person's existing problems worse. Depression17,
anxiety17, and personality disturbances18
have been associated with chronic marijuana use. 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. 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 off19,20,25.
Students who smoke marijuana get lower grades and are less likely to graduate from high school, compared with their nonsmoking peers21,22,23,24.
A study of 129 college students found that, among those who smoked the drug at
least 27 of the 30 days prior to being surveyed, critical skills related to
attention, memory, and learning were significantly impaired, even after the
students had not taken the drug for at least 24 hours20.
These "heavy" marijuana abusers had more trouble sustaining and shifting their
attention and in registering, organizing, and using information than did the
study participants who had abused marijuana no more than 3 of the previous 30
days. As a result, someone who smokes marijuana every day may be functioning at
a reduced intellectual level all of the time.
More recently, the same researchers showed that the ability of a group of long-term heavy marijuana abusers to recall words from a list remained impaired for a week after quitting, but returned to normal within 4 weeks25.
Thus, some cognitive abilities may be restored in individuals who quit smoking
marijuana, even after long-term heavy use.
Workers who smoke marijuana are more likely than their coworkers to have problems on the job. Several studies associate 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 use26.
In another study, heavy marijuana abusers reported that the drug impaired
several important measures of life achievement including cognitive abilities,
career status, social life, and physical and mental health27.
Effects of Exposure During Pregnancy
Research has shown that some babies born to women who abused marijuana during their pregnancies display altered responses to visual stimuli28, increased tremulousness, and a high-pitched cry, which may indicate neurological problems in development29. During the preschool years, marijuana-exposed children have been observed to perform tasks involving sustained attention and memory more poorly than nonexposed children do30,31. In the school years, these children are more likely to exhibit deficits in problem-solving skills, memory, and the ability to remain attentive30.
Addictive Potential
Long-term marijuana abuse can lead to addiction for some people; that is,
they abuse the drug compulsively even though it interferes with family, school,
work, and recreational activities. Drug craving and withdrawal symptoms can make
it hard for long-term marijuana smokers to stop abusing the drug. People trying
to quit report irritability, sleeplessness, and anxiety32.
They also display increased aggression on psychological tests, peaking
approximately one week after the last use of the drug33.
Genetic Vulnerability
Scientists have found that whether an individual has positive or negative sensations after smoking marijuana can be influenced by heredity. A 1997 study
demonstrated that identical male twins were more likely than nonidentical male twins to report similar responses to marijuana abuse, indicating a genetic basis
for their response to the drug34. (Identical
twins share all of their genes.)
It also was discovered that the twins' shared or family environment before age
18 had no detectable influence on their response to marijuana. Certain
environmental factors, however, 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 differentiate experiences of identical
twins were found to have an important effect.34
Treating Marijuana Problems
The latest treatment data indicate that, in 2002, marijuana was the primary drug of abuse in about 15 percent (289,532) of all admissions to treatment facilities in the United States. Marijuana admissions were primarily male (75 percent), White (55 percent), and young (40 percent were in the 15-–19 age range). Those in treatment for primary marijuana abuse had begun use at an early age; 56 percent had abused it by age 14 and 92 percent had abused it by 1835.One study of adult marijuana abusers found comparable benefits from a 14-session cognitive-behavioral group treatment and a 2-session individual treatment that included motivational interviewing and advice on ways to reduce marijuana use. Participants were mostly men in their early thirties who had smoked marijuana daily for more than 10 years. By increasing patients' awareness of what triggers their marijuana abuse, both treatments sought to help patients devise avoidance strategies. Abuse, dependence symptoms, and psychosocial problems decreased for at least 1 year following both treatments; about 30 percent of the patients were abstinent during the last 3-month follow-up period36.
Another study suggests that giving patients vouchers that they can redeem for goods—such as movie passes, sporting equipment, or vocational training—may further improve outcomes37.
Although no medications are currently available for treating marijuana abuse, recent discoveries about the workings of the THC receptors have raised the possibility of eventually developing a medication that will block the intoxicating effects of THC. Such a medication might be used to prevent relapse to marijuana abuse by lessening or eliminating its appeal.
You've suspected drug abuse...and our test could save their life
5 Panel Rapid
Drug Test:
Screening Solutions offers parents a effective, economic means
of testing your child for the presence of illegal drugs. Our instant drug test screens for Cocaine, Methamphetamines,
Marijuana, Opiates and Phencyclidine. Get the answers you need to
make better decisions by home testing.
1
Results from the 2004 National Survey on Drug Use and Health: National Findings
(Office of Applied Studies, NSDUH Series H–27, DHHS Publication No. SMA
05–4061). Rockville, MD, 2004. NSDUH is an annual survey conducted by the
Substance Abuse and Mental Health Services Administration. Copies of the latest
survey are available from the National Clearinghouse for Alcohol and Drug
Information at 800-729-6686.
2 These data are from the annual Drug Abuse Warning Network, funded by the
Substance Abuse and Mental Health Services Administration, DHHS. The survey
provides information about emergency department visits that are induced by or
related to the use of an illicit drug or the nonmedical use of a legal drug. The
latest data are available at 800-729-6686 or online at www.samhsa.gov.
3 These data are from the 2005 Monitoring the Future Survey, funded by the
National Institute on Drug Abuse, National Institutes of Health, DHHS, and
conducted annually by the University of Michigan’s Institute for Social
Research. The survey has tracked 12th-graders’ illicit drug use and related
attitudes since 1975; in 1991, 8th- and 10th-graders were added to the study.
The latest data are online at www.drugabuse.gov.
4 Herkenham M, Lynn A, Little MD, Johnson MR, et al. Cannabinoid receptor
localization in the brain. Proc Natl Acad Sci, USA 87(5):1932–1936, 1990.
5 Rodriguez de Fonseca F, et al. Activation of cortocotropin-releasing factor in
the limbic system during cannabinoid withdrawal. Science 276(5321):2050–2054,
1997.
6 Diana M, Melis M, Muntoni AL, et al. Mesolimbic dopaminergic decline after
cannabinoid withdrawal. Proc Natl Acad Sci 95(17):10269–10273, 1998.
7 Mittleman MA, Lewis RA, Maclure M, et al. Triggering myocardial infarction by
marijuana. Circulation 103(23):2805–2809, 2001.
8 Polen MR, Sidney S, Tekawa IS, et al. Health care use by frequent marijuana
smokers who do not smoke tobacco. West J Med 158(6):596–601, 1993.
9 Tashkin DP. Pulmonary complications of smoked substance abuse. West J Med
152(5):525–530, 1990.
10 Zhang ZF, Morgenstern H, Spitz MR, et al. Marijuana use and increased risk of
squamous cell carcinoma of the head and neck. Cancer Epidemiology, Biomarkers &
Prevention 8(12):1071–1078, 1999.
11 Sridhar KS, Raub WA, Weatherby, NL Jr., et al. Possible role of marijuana
smoking as a carcinogen in the development of lung cancer at a young age.
Journal of Psychoactive Drugs 26(3):285–288, 1994.
12 Hoffman D, Brunnemann KD, Gori GB, et al. On the carcinogenicity of marijuana
smoke. In: VC Runeckles, ed, Recent Advances in Phytochemistry. New York.
Plenum, 1975.
13 Cohen S. Adverse effects of marijuana: Selected issues. Annals of the New
York Academy of Sciences 362:119–124, 1981.
14 Adams IB, Martin BR: Cannabis: pharmacology and toxicology in animals and
humans. Addiction 91(11):1585–1614, 1996.
15 Friedman H, Newton C, Klein TW. Microbial infections, immunomodulation, and
drugs of abuse. Clin Microbiol Rev 16(2):209–219, 2003.
16 Zhu LX, Sharma M, Stolina S, et al. Delta-9-tetrahydrocannabinol inhibits
antitumor immunity by a CB2 receptor-mediated, cytokine-dependent pathway. J
Immunology 165(1):373–380, 2000.
17 Brook JS, Rosen Z, Brook DW. The effect of early marijuana use on later
anxiety and depressive symptoms. NYS Psychologist 35–39, January 2001.
18 Brook JS, Cohen P, Brook DW. Longitudinal study of co-occurring psychiatric
disorders and substance use. J Acad Child and Adolescent Psych 37(3):322–330,
1998.
19 Pope HG, Yurgelun-Todd D. The residual cognitive effects of heavy marijuana
use in college students. JAMA 275(7):521–527, 1996.
20 Block RI, Ghoneim MM. Effects of chronic marijuana use on human cognition.
Psychopharmacology 100(1–2):219–228, 1993.
21 Lynskey M, Hall W. The effects of adolescent cannabis use on educational
attainment: A review. Addiction 95(11):1621–1630, 2000.
22 Kandel DB, Davies M. High school students who use crack and other drugs. Arch
Gen Psychiatry 53(1):71–80, 1996.
23 Rob M, Reynolds I, Finlayson PF. Adolescent marijuana use: Risk factors and
implications. Aust NZ J Psychiatry 24(1):45–56, 1990.
24 Brook JS, Balka EB, Whiteman M. The risks for late adolescence of early
adolescent marijuana use. Am J Public Health 89(10):1549–1554, 1999.
25 Pope HG, Gruber AJ, Hudson JI, et al. Neuropsychological performance in
long-term cannabis users. Arch Gen Psychiatry 58(10):909–915, 2001.
26 Zwerling C, Ryan J, Orav EJ. The efficacy of pre-employment drug screening
for marijuana and cocaine in predicting employment outcome. JAMA
264(20):2639–2643, 1990.
27 Gruber AJ, Pope HG, Hudson JI, et al. Attributes of long-term heavy cannabis
users: A case control study. Psychological Medicine 33(8):1415–1422, 2003.
28 Fried PA, Makin JE. Neonatal behavioural correlates of prenatal exposure to
marihuana, cigarettes and alcohol in a low risk population. Neurotoxicology and
Teratology 9(1):1–7, 1987.
29 Lester BM, Dreher M. Effects of marijuana use during pregnancy on newborn
crying. Child Development 60(23/24):764–771, 1989.
30 Fried PA. The Ottawa prenatal prospective study (OPPS): Methodological issues
and findings. It’s easy to throw the baby out with the bath water. Life Sciences
56(23–24):2159–2168, 1995.
31 Fried PA, Smith AM. A literature review of the consequences of prenatal
marihuana exposure: An emerging theme of a deficiency in aspects of executive
function. Neurotoxicology and Teratology 23(1):1–11, 2001.
32 Kouri EM, Pope HG, Lukas SE. Changes in aggressive behavior during withdrawal
from long-term marijuana use. Psychopharmacology 143(3):302–308, 1999.
33 Haney M, Ward AS, Comer SD, et al. Abstinence symptoms following smoked
marijuana in humans. Psychopharmacology 141(4):395–404, 1999.
34 Lyons MJ, Toomey R, Meyer JM, et al. How do genes influence marijuana use?
The role of subjective effects. Addiction 92(4):409–417, 1997.
35 These data from the Treatment Episode Data Set (TEDS) 2003: Substance Abuse
Treatment Admissions by Primary Substance of Abuse, According to Sex, Age Group,
Race, and Ethnicity, funded by the Substance Abuse and Mental Health Services
Administration, DHHS. The latest data are available at 800-729-6686 or online at
www.samhsa.gov.
36 Stephens RS, Roffman RA, Curtin L. Comparison of extended versus brief
treatments for marijuana use. J Consult Clin Psychol 68(5):898–908, 2000.
37 Budney AJ, Higgins ST, Radonovich KJ, et al. Adding voucher-based incentives
to coping skills and motivational enhancement improves outcomes during treatment
for marijuana dependence. J Consult Clin Psychol 68(6):1051–1061, 2000.
