How does marijuana use affect school, work, and social life? See page 7. from the director: By the time they graduate from Marijuana high school, about 42 percent of teens will have tried marijuana. Although current use among U.S. teens has dropped dramatically in Abuse the past decade (to a prevalence of about 14 percent in 2009), this decline has stalled during the past several years. These data are from the Monitoring the Future study, which has been tracking drug use among teens since 1975. Still, the World Health Organization ranks the United States first among 17 European and North American countries for prevalence of mari- juana use. And more users start every day. In 2008, an estimated 2.2 million Americans used mari- juana for the first time; greater than half were under age 18. The use of marijuana can produce What Is adverse physical, mental, emo- tional, and behavioral effects. It Marijuana? can impair short-term memory and judgment and distort percep- tion. Because marijuana affects M arijuana—often called pot, grass, reefer, weed, herb, brain systems that are still matur- ing through young adulthood, its Mary Jane, or MJ—is a greenish-gray mixture of use by teens may have a negative the dried, shredded leaves, stems, seeds, and flow- effect on their development. And ers of Cannabis sativa—the hemp plant. Most users smoke contrary to popular belief, it can marijuana in hand-rolled cigarettes called joints, among other be addictive. names; some use pipes or water pipes called bongs. Marijuana We hope that this Research Report cigars, or blunts, are also popular. To make blunts, users slice will help make readers aware open cigars, remove some of the tobacco, and mix the remain- of our current knowledge of marijuana abuse and its harmful der with marijuana (Timberlake 2009). Marijuana also is used effects. to brew tea and sometimes is mixed into foods. Nora D. Volkow, M.D. continued inside Director National Institute on Drug Abuse Marijuana Research Report Series Abuse What Is the Long-Term Trends in Annual* Marijuana Use Scope of Among 8th, 10th, and 12th Graders Marijuana Use 40 in the United 35 12th-graders States? 30 Marijuana is the most commonly nt 10th-graders used illicit drug (15.2 million e c past-month users) according to Per 25 the 2008 National Survey on Drug 20 Use and Health (NSDUH). That year, marijuana was used by 75.6 15 percent of current illicit drug users 8th-graders (defined as having used the drug 10 some time in the 30 days before the 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 survey) and was the only drug used *use in the past 12 months Source: 2009 Monitoring the Future Survey by 53.3 percent of them. Marijuana use is widespread among adolescents and young in the past decade among 8th-, How Does adults. According to the Monitor- 10th-, and 12th-graders. However, ing the Future Survey—an annual this decline has stalled in the past Marijuana survey of attitudes and drug use few years as attitudes have soft- Produce its among the Nation’s middle and ened about marijuana’s risks. In Effects? high school students—most mea- 2009, 11.8 percent of 8th-graders sures of marijuana use decreased reported marijuana use in the past Delta-9-tetrahydrocannabinol year, and 6.5 percent were current (THC) is the main active ingredient users. Among 10th-graders, 26.7 in marijuana, responsible for percent had used marijuana in the many of its known effects. When past year, and 15.9 percent were marijuana is smoked, its effects current users. Rates of use among begin almost immediately. THC 12th-graders were higher still: 32.8 rapidly passes from the lungs into percent had used marijuana during the bloodstream, which carries the the year prior to the survey, and chemical to organs throughout 20.6 percent were current users. the body, including the brain. The The Drug Abuse Warning Net- effects of smoked marijuana can work (DAWN), a system for moni- last from 1 to 3 hours. If marijuana toring the health impact of drugs, is consumed in foods or beverages, estimated that in 2008, marijuana the effects appear later—usually in was a contributing factor in over 30 minutes to 1 hour—but can last 374,000 emergency department up to 4 hours. Smoking marijuana (ED) visits in the United States, delivers significantly more THC with about two-thirds of patients into the bloodstream than eating being male, and 13 percent between or drinking the drug. the ages of 12 and 17. 2 NIDA Research Report Series Marijuana’s Effects on the Brain © Alice Y. Chen, 2004. Adapted from Scientific American. When marijuana is smoked, its active ingredient, THC, travels throughout the body, including the brain, to produce its many effects. THC attaches to sites called cannabinoid receptors on nerve cells in the brain, affecting the way those cells work. Cannabinoid receptors are abundant in parts of the brain that regulate movement, coordination, learning and memory, higher cognitive functions such as judgment, and pleasure. Scientists have learned a great function of the natural, or all the consequences to the brain deal about how THC acts in the endogenous, cannabinoids. An and body when exposed to higher brain. THC binds to specific overstimulation of these receptors concentrations of THC. sites called cannabinoid receptors in key brain areas produces the (CBRs) located on the surface of marijuana “high,” as well as other How Does nerve cells. These receptors are effects on mental processes. Over Marijuana Use found in high-density in areas of time, this overstimulation can the brain that influence pleasure, alter the function of CBRs, which, Affect Your Brain memory, thinking, concentration, along with other changes in the and Body? movement, coordination, and brain, can lead to addiction and to sensory and time perception. withdrawal symptoms when drug Effects on the Brain CBRs are part of a vast use stops. As THC enters the brain, it causes communication network known The THC content or potency the user to feel euphoric—or as the endocannabinoid system, of marijuana, as detected in high—by acting on the brain’s which plays a critical role in confiscated samples over the past reward system, which is made up normal brain development and 30+ years (Potency Monitoring of regions that govern the response function. In fact, THC effects Project, University of Mississippi), to pleasurable things like sex and are similar to those produced by has been steadily increasing. This chocolate, as well as to most drugs naturally occurring chemicals increase raises concerns that the of abuse. THC activates the reward found in the brain (and body) consequences of marijuana use system in the same way that nearly called endogenous cannabinoids. could be worse than in the past, all drugs of abuse do: by stimulat- These chemicals help control many particularly among new users, or in ing brain cells to release the chemi- of the same mental and physical young people, whose brains are still cal dopamine. functions that may be disrupted by developing. We still do not know, Along with euphoria, re- marijuana use. however, whether cannabis users laxation is another frequently When someone smokes adjust for the increase in potency reported effect in human studies. marijuana, THC stimulates the by using less or by smoking it Other effects, which vary dramati- CBRs artificially, disrupting differently. We also do not know 3 NIDA Research Report Series Marijuana users who have taken large doses of the drug may experience an acute psychosis, which includes hallucinations, delusions, and a loss of the sense of personal identity. cally among different users, include Marijuana users who have chronic cannabis use affects brain heightened sensory perception taken large doses of the drug may structure, for example, have been (e.g., brighter colors), laughter, experience an acute psychosis, inconsistent. It may be that the altered perception of time, and which includes hallucinations, effects are too subtle for reliable increased appetite. After a while, delusions, and a loss of the sense detection by current techniques. A the euphoria subsides, and the of personal identity. Although the similar challenge arises in studies user may feel sleepy or depressed. specific causes of these symptoms of the effects of chronic marijuana Occasionally, marijuana use may remain unknown, they appear to use on brain function. Although produce anxiety, fear, distrust, or occur more frequently when a high imaging studies (functional MRI; panic. dose of cannabis is consumed in fMRI) in chronic users do show Marijuana use impairs a per- food or drink rather than smoked. some consistent alterations, the re- son’s ability to form new memories Such short-term psychotic reac- lation of these changes to cognitive (see below, “Marijuana, Memory, tions to high concentrations of functioning is less clear. This un- and the Hippocampus”) and to shift THC are distinct from longer- certainty may stem from confound- focus. THC also disrupts coordina- lasting, schizophrenia-like disor- ing factors such as other drug use, tion and balance by binding to re- ders that have been associated with residual drug effects (which can oc- ceptors in the cerebellum and basal the use of cannabis in vulnerable cur for at least 24 hours in chronic ganglia—parts of the brain that individuals. (See section on the link users), or withdrawal symptoms in regulate balance, posture, coordi- between marijuana use and mental long-term chronic users. nation, and reaction time. There- illness, page 6.) An enduring question in the fore, learning, doing complicated Our understanding of mari- field is whether individuals who tasks, participating in athletics, and juana’s long-term brain effects is quit marijuana, even after long- driving are also affected. limited. Research findings on how term, heavy use, can recover some Marijuana, Memory, and the Hippocampus Memory impairment from tional changes in the hippocam- marijuana use occurs because pus from THC exposure during THC alters how information is adolescence. processed in the hippocampus, a brain area responsible for mem- As people age, they lose neu- ory formation. rons in the hippocampus, which decreases their ability to learn Most of the evidence support- new information. Chronic THC ing this assertion comes from exposure may hasten age-related animal studies. For example, rats loss of hippocampal neurons. In exposed to THC in utero, soon one study, rats exposed to THC Distribution of cannabinoid receptors in the rat brain. after birth, or during adolescence, every day for 8 months (approxi- Brain image reveals high levels (shown in orange show notable problems with mately 30 percent of their life- and yellow) of cannabinoid receptors in many areas, including the cortex, hippocampus, cerebellum, and specific learning/memory tasks span) showed a level of nerve cell nucleus accumbens (ventral striatum). later in life. Moreover, cognitive loss (at 11 to 12 months of age) impairment in adult rats is associ- that equaled that of unexposed ated with structural and func- animals twice their age. 4 NIDA Research Report Series of their cognitive abilities. One study reports that the ability of Consequences of long-term heavy marijuana users to Marijuana Abuse recall words from a list was still im- paired 1 week after they quit using, Acute (present during intoxication) but returned to normal by 4 weeks. • Impairs short-term memory However, another study found that • Impairs attention, judgment, and other cognitive functions marijuana’s effects on the brain can • Impairs coordination and balance build up and deteriorate critical life • Increases heart rate skills over time. Such effects may • Psychotic episodes be worse in those with other men- Persistent (lasting longer than intoxication, tal disorders, or simply by virtue of but may not be permanent) the normal aging process. • Impairs memory and learning skills • Sleep impairment Effects on General Physical Health Long-term (cumulative effects of chronic abuse) Within a few minutes after inhaling • Can lead to addiction marijuana smoke, an individual’s • Increases risk of chronic cough, bronchitis heart rate speeds up, the bron- • Increases risk of schizophrenia in vulnerable individuals chial passages relax and become • May increase risk of anxiety, depression, and amotivational syndrome* enlarged, and blood vessels in the eyes expand, making the eyes look * These are often reported co-occurring symptoms/disorders with chronic marijuana use. However, research has not yet determined whether red. The heart rate—normally 70 marijuana is causal or just associated with these mental problems. to 80 beats per minute—may in- crease by 20 to 50 beats per minute, or may even double in some cases. Taking other drugs with marijuana boomer generation, who may have Even infrequent marijuana use can can amplify this effect. other cardiovascular risks that may cause burning and stinging of the Limited evidence suggests increase their vulnerability. mouth and throat, often accompa- that a person’s risk of heart attack The smoke of marijuana, like nied by a heavy cough. One study during the first hour after smoking that of tobacco, consists of a toxic found that extra sick days used by marijuana is four times his or her mixture of gases and particulates, frequent marijuana smokers were usual risk. This observation could many of which are known to be often because of respiratory ill- be partly explained by marijuana harmful to the lungs. Someone nesses (Polen et al. 1993). raising blood pressure (in some who smokes marijuana regu- In addition, marijuana has cases) and heart rate and reduc- larly may have many of the same the potential to promote cancer of ing the blood’s capacity to carry respiratory problems that tobacco the lungs and other parts of the oxygen. Such possibilities need to smokers do, such as daily cough respiratory tract because it con- be examined more closely, par- and phlegm production, more tains irritants and carcinogens—up ticularly since current marijuana frequent acute chest illnesses, and to 70 percent more than tobacco users include adults from the baby a greater risk of lung infections. smoke. It also induces high levels Within a few minutes after inhaling marijuana smoke, an individual’s heart rate speeds up, the bronchial passages relax and become enlarged, and blood vessels in the eyes expand, making the eyes look red. 5 NIDA Research Report Series of an enzyme that converts certain unidentified active ingredient in disorders in humans. One short hydrocarbons into their cancer- cannabis smoke having protective (3-week) study found marijuana causing form, which could accel- properties—if corroborated and smoking to be associated with a erate the changes that ultimately properly characterized—could help few statistically significant nega- produce malignant cells. And explain the inconsistencies and tive effects on the immune function since marijuana smokers generally modest findings. of AIDS patients; a second small inhale more deeply and hold their A significant body of research study of college students also sug- breath longer than tobacco smok- demonstrates negative effects of gested the possibility of marijuana ers, the lungs are exposed longer THC on the function of vari- having adverse effects on immune to carcinogenic smoke. However, ous immune cells, both in vitro in system functioning. Thus, the while several lines of evidence have cells and in vivo with test animals. combined evidence from animal suggested that marijuana use may However, no studies to date con- studies plus the limited human lead to lung cancer, the supporting nect marijuana’s suspected immune data available, seem to warrant ad- evidence is inconclusive (Hashibe system suppression with greater ditional research on the impact of et al. 2006). The presence of an incidence of infections or immune marijuana on the immune system. (See also “The Science of Medical Marijuana,” page 9.) Genetic variation in COMT influences Is There a the harmful effects of abused drugs Link Between 20 Marijuana Use m No adolescent cannabis use or Adolescent cannabis use and Mental f ni Illness? e615 r2 phe Research in the past decade has g o a hizat 10 focused on whether marijuana scer use actually causes other mental h d illnesses. The strongest evidence witsor to date suggests a link between nt di 5 cannabis use and psychosis e c (Hall and Degenhardt 2009). r e P For example, a series of large 0 prospective studies that followed a n= (151) (48) (311) (91) (148) (54) Met/Met Val/Met Val/Val group of people over time showed COMT genotype a relationship between marijuana use and later development of Adapted from Caspi et al., Biol Psychiatry, May 2005. psychosis. Marijuana use also The influence of adolescent marijuana use on adult psychosis is affected by worsens the course of illness in genetic variables. This figure shows that variations in a gene can affect the patients with schizophrenia and likelihood of developing psychosis in adulthood, following exposure to cannabis can produce a brief psychotic in adolescence. The COMT gene governs an enzyme that breaks down dopa- mine, a brain chemical involved in schizophrenia. It comes in two forms: “Met” reaction in some users that fades and “Val.” Individuals with one or two copies of the Val variant have a higher as the drug wears off. The amount risk of developing schizophrenic-type disorders if they used cannabis during of drug used, the age at first use, adolescence (dark bars). Those with only the Met variant were unaffected by and genetic vulnerability can all cannabis use. influence this relationship. One example is a study (illustrated, page 6 NIDA Research Report Series 6) that found an increased risk of How Does psychosis among adults who had used marijuana in adolescence Marijuana Use and who also carried a specific Affect School, variant of the gene for catechol- Work, and O-methyltransferase (COMT) Social Life? (Caspi et al. 2005), an enzyme that degrades neurotransmitters such as Research has shown that mari- dopamine and norepinephrine. juana’s negative effects on atten- In addition to the observed tion, memory, and learning can links between marijuana use last for days or weeks after the and schizophrenia, other less acute effects of the drug wear off consistent associations have been (Schweinsburg et al. 2008). Con- reported between marijuana use sequently, someone who smokes and depression, anxiety, suicidal marijuana daily may be func- thoughts among adolescents, tioning at a reduced intellectual and personality disturbances. level most or all of the time. Not One of the most frequently cited, surprisingly, evidence suggests that, albeit still controversial, is an found that the twin who had used compared with their nonsmok- amotivational syndrome, defined marijuana before the age of 17 ing peers, students who smoke as a diminished or absent drive had elevated rates of other drug marijuana tend to get lower grades to engage in typically rewarding use and drug problems later on, and are more likely to drop out of activities. Because of the role of compared with their twin who did high school (Fergusson and Boden the endocannabinoid system in not use before age 17. 2008). A meta-analysis of 48 regulating mood, these associations According to the 2008 relevant studies—one of the most make a certain amount of sense; NSDUH, marijuana accounted thorough performed to date— however, more research is needed for 4.2 million of the estimated 7 found cannabis use to be associated to confirm and better understand million Americans dependent on consistently with reduced educa- these linkages. or abusing illicit drugs. In 2008, tional attainment (e.g., grades and approximately 15 percent of people chances of graduating) (Macleod entering drug abuse treatment et al. 2004). However, a causal rela- Is Marijuana programs reported marijuana tionship is not yet proven between Addictive? as their primary drug of abuse; cannabis use by young people and Long-term marijuana use can 61 percent of persons under psychosocial harm. lead to addiction; that is, people 15 reported marijuana as their That said, marijuana users have difficulty controlling their primary drug of abuse, as did 56 themselves report poor outcomes drug use and cannot stop even percent of those 15 to 19 years old. on a variety of life satisfaction and though it interferes with many Marijuana addiction is achievement measures. One study aspects of their lives. It is estimated also linked to a withdrawal compared current and former long- that 9 percent of people who use syndrome similar to that of term heavy users of marijuana marijuana will become dependent nicotine withdrawal, which can with a control group who reported on it. The number goes up to make it hard to quit. People smoking cannabis at least once in about 1 in 6 in those who start trying to quit report irritability, their lives but not more than 50 using young (in their teens) and to sleeping difficulties, craving, and times. Despite similar education 25–50 percent among daily users. anxiety. They also show increased and income backgrounds, sig- Moreover, a study of over 300 aggression on psychological tests, nificant differences were found in fraternal and identical twin pairs peaking approximately 1 week educational attainment: fewer of after they last used the drug. the heavy users of cannabis com- 7 NIDA Research Report Series pleted college, and more had yearly and Johnston 2007; Richer and the drug-specific factors from the household incomes of less than Bergeron 2009). According to the environmental ones (Schempf and $30,000. When asked how marijua- National Highway Traffic Safety Strobino 2008). na affected their cognitive abilities, Administration, drugs other than career achievements, social lives, alcohol (e.g., marijuana and Available and physical and mental health, cocaine) are involved in about 18 the majority of heavy cannabis percent of motor vehicle driver Treatments for users reported the drug’s negative deaths. A recent survey found Marijuana Use effects on all of these measures. that 6.8 percent of drivers, mostly Disorders In addition, several studies have under 35, who were involved in linked workers’ marijuana smoking accidents tested positive for THC; Marijuana dependence appears to with increased absences, tardiness, alcohol levels above the legal limit be very similar to other substance accidents, workers’ compensa- were found in 21 percent of such dependence disorders, although tion claims, and job turnover. For drivers. the long-term clinical outcomes example, a study among postal may be less severe. On average, workers found that employees who adults seeking treatment for Can Marijuana tested positive for marijuana on marijuana abuse or dependence a pre-employment urine drug test Use During have used marijuana nearly every had 55 percent more industrial Pregnancy Harm day for more than 10 years and accidents, 85 percent more injuries, have attempted to quit more than the Baby? and a 75-percent increase in absen- six times. It is important to note teeism compared with those who Animal research suggests that the that marijuana dependence is most tested negative for marijuana use. body’s endocannabinoid system prevalent among patients suffering plays a role in the control of from other psychiatric disorders, brain maturation, particularly in particularly among adolescent Does Marijuana the development of emotional and young adult populations Use Affect responses. It is conceivable that (Gouzoulis-Mayfrank 2008). Also, Driving? even low concentrations of marijuana abuse or dependence THC, when administered during typically co-occurs with use of Because marijuana impairs judg- the perinatal period, could other drugs, such as cocaine and ment and motor coordination and have profound and long-lasting alcohol. Available studies indicate slows reaction time, an intoxicated consequences for both brain and that effectively treating the mental person has an increased chance of behavior (Trezza et al. 2008). health disorder with standard being involved in and being respon- Research has shown that some treatments involving medications sible for an accident (O’Malley babies born to women who used and behavioral therapies may help marijuana during their pregnancies reduce cannabis use, particularly display altered responses to visual among heavy users and those with stimuli, increased tremulousness, more chronic mental disorders. and a high-pitched cry, which Behavioral treatments, such could indicate problems with as motivational enhancement neurological development. In therapy (MET), group or school, marijuana-exposed individual cognitive-behavioral children are more likely to show therapy (CBT), and contingency gaps in problemsolving skills, management (CM), as well as memory, and the ability to family-based treatments, have remain attentive. More research shown promise. is needed, however, to disentangle 8 NIDA Research Report Series Unfortunately, the success rates of treatment are rather modest. Even with the most effective treatment for adults, only about 50 percent of enrollees The Science of Medical Marijuana achieve an initial 2-week period of abstinence, and among those who do, approximately half will resume use within a year. Across studies, 1-year abstinence rates have ranged between 10 and 30 percent for the various behavioral approaches. As with other addictions, these data suggest that a chronic care model should be considered for marijuana addiction, with treatment intensity The potential medicinal properties of marijuana have been the stepped up or down based on subject of substantive research and heated debate. Scientists have need, comorbid addictions or confirmed that the cannabis plant contains active ingredients other mental disorders, and the with therapeutic potential for relieving pain, controlling nausea, availability of family and other stimulating appetite, and decreasing ocular pressure. As a result, supports. a 1990 Institute of Medicine report concluded that further clinical Currently, no medications research on cannabinoid drugs and safe delivery systems was are available to treat marijuana warranted. abuse, but research is active in this area. Most of the studies At that time, dronabinol (Marinol®) and nabilone (Cesamet®) to date have targeted the were the only FDA-approved, marijuana-based medications that marijuana withdrawal syndrome. doctors could prescribe for the treatment of nausea in patients For example, a recent human undergoing cancer chemotherapy and to stimulate appetite laboratory study showed that a in patients with wasting syndrome due to AIDS. These pills combination of a cannabinoid contained synthetic versions of THC, the main active ingredient in agonist medication with lofexidine marijuana. Today, 25 years after their approval, the development (a medication approved in the of Sativex® marks the arrival of the second generation of United Kingdom for the treatment cannabis-based medications. This new product (currently of opioid withdrawal) produced available in the United Kingdom and Canada) is a chemically pure more robust improvements in mixture of plant-derived THC and Cannabidiol, formulated as a sleep and decreased marijuana mouth spray and approved for the relief of cancer-associated pain withdrawal, craving, and relapse and spasticity and neuropathic pain in multiple sclerosis. in daily marijuana smokers relative to either medication alone. Scientists continue to investigate the medicinal properties of Recent discoveries about the THC and other cannabinoids to better evaluate and harness inner workings of the endogenous their ability to help patients suffering from a broad range cannabinoid system raise the of conditions, while avoiding the adverse effects of smoked future possibility of a medication marijuana. These efforts are bound to improve our understanding able to block THC’s intoxicating of the cannabinoid system and help us bring to market a new effects, which could help prevent generation of safe and effective medications. relapse by reducing or eliminating marijuana’s appeal. 9 NIDA Research Report Series Glossary Addiction: A chronic, relapsing disease Dopamine: A brain chemical, classified as a characterized by compulsive drug seeking and neurotransmitter, found in regions of the brain use and by long-lasting changes in the brain. that regulate movement, emotion, motivation, and pleasure. Basal Ganglia: Structures located deep in the brain that play an important role in the initiation Hippocampus: A seahorse-shaped structure of movements. These clusters of neurons include located within the brain that is considered an the caudate nucleus, putamen, globus pallidus, important part of the limbic system. One of the and substantia nigra. It also contains the nucleus most studied areas of the brain, the hippocampus accumbens, which is the main center of reward in plays key roles in learning, memory, and the brain. emotion. Cerebellum: A large structure located in the back Hydrocarbon: Any chemical compound of the brain that helps control the coordination containing only hydrogen and carbon. of movement by making connections to other parts of the CNS (pons, medulla, spinal cord, and Motivational Enhancement Therapy (MET): A thalamus). It also may be involved in aspects of systematic form of intervention designed to motor learning. produce rapid, internally motivated change. MET does not attempt to treat the person, but rather Cerebral Cortex: The outermost layer of the mobilize their own internal resources for change cerebral hemispheres of the brain. It is largely and engagement in treatment. responsible for conscious experience, including perception, emotion, thought, and planning. Psychosis: A mental disorder (e.g., schizophrenia) characterized by delusional or disordered Cannabinoids and Cannabinoid Receptors: thinking detached from reality; symptoms often A family of chemicals that bind to specific include hallucinations. (cannabinoid) receptors to influence mental and physical functions. Cannabinoids that are Schizophrenia: A psychotic disorder characterized produced naturally by the body are referred to by symptoms that fall into two categories: as endocannabinoids. They play important roles (1) positive symptoms, such as distortions in in development, memory, pain, appetite, among thoughts (delusions), perception (hallucinations), others. The marijuana plant (Cannabis sativa) and language and thinking and (2) negative contains delta-9-tetrahydrocannabinol (THC) symptoms, such as flattened emotional that can disrupt these processes, if administered responses and decreased goal-directed behavior. repeatedly and/or in high enough concentrations. Schizophreniform Disorders: Similar to Carcinogen: Any substance that causes cancer. schizophrenia, but of shorter duration and possibly lesser severity. Cognitive-Behavioral Therapy (CBT): A form of psychotherapy that teaches people strategies THC: Delta-9-tetrahydrocannabinol; the main to identify and correct problematic behaviors active ingredient in marijuana, which acts on the in order to enhance self-control, stop drug use, brain to produce its effects. and address a range of other problems that often Ventral Striatum: An area of the brain that is part co-occur with them. of the basal ganglia and becomes activated and Contingency Management (CM): A therapeutic flooded with dopamine in the presence of salient management approach based on frequent stimuli. The release of this chemical also occurs monitoring of the target behavior and the during physically rewarding activities such as provision (or removal) of tangible, positive eating, sex, and taking drugs, and is a key factor rewards when the target behavior occurs (or behind our desire to repeat these activities. does not). CM techniques have shown to be Withdrawal: Adverse symptoms that occur after effective for keeping people in treatment and chronic use of a drug is reduced or stopped. promoting abstinence. 10 NIDA Research Report Series