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NIH: Is marijuana addictive? - Yes, You Can Become Addicted to Marijuana.
And the Problem is Growing.
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Stateline Article June 6, 2018
By: Christine Vestal
http://www.pewtrusts.org/en/research-and-analysis/blogs/stateline/2018/06/06/yes-you-can-become-addicted-to-marijuana-and-the-problem-is-growing
Quintin Pohl, 17, under a statue of Louis Pasteur well-known among pot smokers, at San Rafael High School in Northern California. Addiction specialists there are seeing increased demand for marijuana addiction treatment.
The Pew Charitable Trusts
SAN RAFAEL, Calif. - For as long as most residents can remember, smoking marijuana has been a part of life here. The fact that California legalized the practice in January went practically unnoticed in this quiet town a half-hour's drive north of San Francisco, where some claim the normalization of America's marijuana culture got its start.
For Quintin Pohl and countless teenagers before him, smoking pot was a rite of passage. It was a diversion from the loneliness he felt at home when his parents were splitting up and a salve for middle-school angst. It was his entire social life in seventh and eighth grades, when social life is everything.
Even though nearly all his friends were using marijuana and seeming to enjoy it, Pohl said, at some point his marijuana use took a turn he never saw coming: He became addicted.
Many people are unaware of marijuana addiction. But in the public health and medical communities, it is a well-defined disorder that includes physical withdrawal symptoms, cravings and psychological dependence. Many say it is on the rise, perhaps because of the increasing potency of genetically engineered plants and the use of concentrated products, or because more marijuana users are partaking multiple times a day.
"There should be no controversy about the existence of marijuana addiction," said Dr. David Smith, who has been treating addiction since the 1960s when he opened a free clinic in San Francisco's drug-drenched Haight-Ashbury neighborhood. "We see it every day. The controversy should be why it appears to be affecting more people."
Although estimates of the number of people who have ever tried marijuana or who use it regularly vary widely from survey to survey, the federal government and the marijuana industry tend to agree that total marijuana use has remained relatively constant over the past decade. Increased use in the past three years has been slight, despite increased commercial availability in states that have legalized it.
The percentage of people who become addicted to marijuana - about 9 percent of all users, and about 17 percent of those who start in adolescence - also has been stable.
Yet here in Northern California, some addiction treatment practitioners say they're seeing something new - a surge in demand for marijuana addiction treatment, particularly among adolescents, even though national surveys show little to no increase in the number of adults using the substance, and some studies show a decline in marijuana use among adolescents.
At fewer than 1 in 10 users, marijuana's estimated rate of addiction is lower than cocaine and alcohol (15 percent) and heroin (25 percent). Unlike opioids and stimulants, marijuana dependence tends to develop slowly: Months or years may pass before debilitating symptoms begin to negatively affect the average dependent user's life.
To be sure, there are no known reports of anyone dying of a marijuana overdose or its commonly experienced withdrawal symptoms - chills, sweats, cravings, insomnia, loss of appetite, nausea, anxiety and irritability.
Still, since so many Americans use marijuana recreationally - more than any other mood-altering substance other than alcohol - the number of people who develop a dependence on it is substantial. According to Nora Volkow, director of the National Institute on Drug Abuse, an estimated 2.7 million Americans meet the diagnostic criteria for marijuana dependence, second only to alcohol dependence.
Potency and Frequency
About 20 miles north of here, at Muir Wood Adolescent and Family Services, where Pohl eventually got treatment as he entered his senior year in high school, Smith, a visiting physician there, said the number of patients seeking help for marijuana dependence has more than doubled in the last two years.
And he doesn't think the increased demand can be explained by greater public awareness of addiction or improved access to treatment. Smith speculates that it's the potency of concentrated products that's causing a higher prevalence of problematic marijuana use.
"Back in the day when kids were sitting around smoking a joint, the THC levels found in marijuana averaged from 2 to 4 percent," Smith said. "That's what most parents think is going on today. And that's why society thinks marijuana is harmless."
But selective breeding has resulted in an average marijuana potency of 20 percent THC, the primary psychoactive compound in marijuana. Some strains exceed 30 percent.
Marijuana concentrates and extracts, much more commonly used in the last five years, have THC levels that range from 40 to more than 80 percent, according to marijuana industry promotional information and Drug Enforcement Administration reports.
Other addiction specialists say that although the number of marijuana users may not be rising significantly, the percentage of users who use it multiple times a day is increasing, which may also be contributing to higher rates of dependence. According to the National Institute on Drug Abuse, daily use among young adults is at the highest rate in more than 30 years.
In general, only about 5 percent of people with marijuana addiction get specialized treatment, compared with nearly a quarter of those with an opioid addiction, according to the Substance Abuse and Mental Health Services Administration.
Federal officials are trying to increase awareness.
Dr. Elinore McCance-Katz, an addiction physician and director of the substance abuse administration told Stateline in an interview that she plans to be the first director of the agency in any administration to speak out about the dangers of marijuana and correct what she says is "rampant misinformation" being spread by the marijuana industry.
Susan Weiss, who directs research on the health effects of marijuana at the National Institute on Drug Abuse, told a group of addiction doctors at the annual meeting of the American Society of Addiction Medicine in April that the federal government is trying to get the message out that marijuana can be addictive.
"But believe it or not," she told the group, "we're having a hard time convincing people that addiction exists."
The National Cannabis Industry Association's chief spokesman, Morgan Fox, said he's not surprised the federal government is having a hard time convincing the public that marijuana can be addictive.
"It's their own fault," he said of the government. "When people find out they've been lied to by the federal government about the relative harms of marijuana for decades, they are much less likely to believe anything they have to say going forward even if that information is accurate."
Fox said his organization has no disagreement with the scientific finding that about 9 percent of people who use marijuana become addicted, and his organization urges its members to make that clear in their marketing information. But he disagrees that more potent forms of marijuana may be causing an increase in addiction. "It just means people need to consume less to achieve the desired effect," he said.
So far, no scientific studies have shown that stronger pot increases the likelihood of addiction, and large swaths of the general public continue to question the existence of marijuana addiction. But for Quintin Pohl, addiction was real.
Quintin's Story
Pohl said his marijuana addiction took years to develop. His mother, Kimberly Thomas, said that once she realized her son was using marijuana frequently, "it was like a roller coaster chugging up hill, chugging, chugging, chugging. You know something is happening," she said, "and then just within a couple of days, you reach the peak and zoom downhill. It was awful, awful."
Scott Sowle, director of the Muir Wood center, where Pohl got treatment, said he gets the same call from parents nearly every day.
"It's like Groundhog Day," he said. "They call and say, 'My 16-year-old son was doing really well in school. He was interested in sports and involved in extracurricular activities. But suddenly, he's just not the same kid anymore.'"
Pohl recalled that he drank a little, off and on, but that marijuana was his constant obsession. After middle school, he got involved in rowing for a couple of years and took a break from his marijuana friend group. But after he decided competitive rowing wasn't for him, Pohl said he started smoking pot again, this time with a new group of friends who smoked all the time.
And then the roller coaster plunged.
His grades plummeted; he stopped going home most of the time and was couch surfing for a while. Finally, he said, his mom called the cops on him for stealing her car. "At that point, I was heartless, emotionless," he said. "I was just kind of a blob taking up space. I was baked 24/7."
Pohl's mother said she saw that he was in trouble and demanded that he stay at home every moment he wasn't in school. (Pohl's father was living in San Francisco and his sister was away at college.)
"She told me to come back home. So, I did," Pohl said. "At the time, I wasn't sure why she did that. I was still in that whole miserable phase, smoking at least an ounce of weed a week - two ounces on a good week." (One ounce is enough to smoke four to eight joints every day for a week, depending on their size.)
Then early one morning before school, Pohl recalled, "I got out of the shower with a towel around my waist. I walked from the bathroom into my bedroom. There was steam everywhere. But through the haze, I could see two big guys in my room in leather jackets, two really big guys.
"They said, 'Get dressed, young man, and come with us.'"
They were private investigators his mother hired to take him to Muir Wood.
Pohl said he went through a week of pure misery at Muir Wood: angry, in denial and suffering. "I couldn't sleep for a week. I was cold and then I was sweating. I hated everything," he said. "And then the sun hit my face one morning and it felt great. Things tasted good, smelled better, everything was just enhanced."
During his six weeks at Muir Wood, Pohl took intensive classes with about 10 other boys and talked to his therapist frequently. His mother spent eight hours a week there, attending parent classes, sharing meals with her son, and working with him and his therapist to address the underlying issues that led him to self-medicate with marijuana.
Pohl says he hasn't smoked marijuana since he left Muir Wood last July and hasn't had any desire to. For the rest of the summer and after school in the fall, he attended classes at a Muir Wood outpatient clinic in San Rafael.
"In general, kids who come out of residential and go through an outpatient program and then go to meetings for sober teens are pretty successful," Sowle said. "It's the kids who don't have a continuing care program and whose parents think a short stint in a residential program is a cure-all who aren't so successful."
Wearing black pants, a black sweatshirt and a pink skull cap on a cool but sunny day in late May, Pohl smiles broadly when he talks about his future. He graduates June 14 and plans to start working full time at the grocery store where he's had a part-time job for the last year. He also plans to move to Petaluma and share a house with friends, he said. "I like it up there in cow country."
As for smoking marijuana again, Pohl is confident he'll be able to smoke socially when he's an adult. He plans to stay in Northern California and can't picture not smoking pot when he grows up.
Squatting under a statue of Louis Pasteur at San Rafael High School, he proudly explains his town's place in marijuana history. In 1971, he says, a group of high school kids who called themselves the Waldos met at the statue every day at 4:20 p.m. to smoke pot.
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Is marijuana addictive?
https://www.drugabuse.gov/publications/research-reports/marijuana/marijuana-addictive
Marijuana use can lead to the development of problem use, known as a marijuana use disorder, which takes the form of addiction in severe cases. Recent data suggest that 30 percent of those who use marijuana may have some degree of marijuana use disorder.18 People who begin using marijuana before the age of 18 are four to seven times more likely to develop a marijuana use disorder than adults.19
Marijuana use disorders are often associated with dependence-in which a person feels withdrawal symptoms when not taking the drug. People who use marijuana frequently often report irritability, mood and sleep difficulties, decreased appetite, cravings, restlessness, and/or various forms of physical discomfort that peak within the first week after quitting and last up to 2 weeks.20,21 Marijuana dependence occurs when the brain adapts to large amounts of the drug by reducing production of and sensitivity to its own endocannabinoid neurotransmitters.22,23
Marijuana use disorder becomes addiction when the person cannot stop using the drug even though it interferes with many aspects of his or her life. Estimates of the number of people addicted to marijuana are controversial, in part because epidemiological studies of substance use often use dependence as a proxy for addiction even though it is possible to be dependent without being addicted. Those studies suggest that 9 percent of people who use marijuana will become dependent on it,24,25 rising to about 17 percent in those who start using in their teens.26,27
In 2015, about 4.0 million people in the United States met the diagnostic criteria for a marijuana use disorder;3 138,000 voluntarily sought treatment for their marijuana use.28
Rising Potency
Marijuana potency, as detected in confiscated samples, has steadily increased over the past few decades.2 In the early 1990s, the average THC content in confiscated marijuana samples was roughly 3.8 percent. In 2014, it was 12.2 percent. The average marijuana extract contains more than 50 percent THC, with some samples exceeding 80 percent. These trends raise concerns that the consequences of marijuana use could be worse than in the past, particularly among those who are new to marijuana use or in young people, whose brains are still developing (see "What are marijuana's long-term effects on the brain?").
Researchers do not yet know the full extent of the consequences when the body and brain (especially the developing brain) are exposed to high concentrations of THC or whether the recent increases in emergency department visits by people testing positive for marijuana are related to rising potency. The extent to which people adjust for increased potency by using less or by smoking it differently is also unknown. Recent studies suggest that experienced people may adjust the amount they smoke and how much they inhale based on the believed strength of the marijuana they are using, but they are not able to fully compensate for variations in potency.30,31
Is marijuana a gateway drug?
Some research suggests that marijuana use is likely to precede use of other licit and illicit substances46 and the development of addiction to other substances. For instance, a study using longitudinal data from the National Epidemiological Study of Alcohol Use and Related Disorders found that adults who reported marijuana use during the first wave of the survey were more likely than adults who did not use marijuana to develop an alcohol use disorder within 3 years; people who used marijuana and already had an alcohol use disorder at the outset were at greater risk of their alcohol use disorder worsening.47 Marijuana use is also linked to other substance use disorders including nicotine addiction.
Early exposure to cannabinoids in adolescent rodents decreases the reactivity of brain dopamine reward centers later in adulthood.48 To the extent that these findings generalize to humans, this could help explain the increased vulnerability for addiction to other substances of misuse later in life that most epidemiological studies have reported for people who begin marijuana use early in life.49 It is also consistent with animal experiments showing THC's ability to "prime" the brain for enhanced responses to other drugs.50 For example, rats previously administered THC show heightened behavioral response not only when further exposed to THC but also when exposed to other drugs such as morphine-a phenomenon called cross-sensitization.51
These findings are consistent with the idea of marijuana as a "gateway drug." However, the majority of people who use marijuana do not go on to use other, "harder" substances. Also, cross-sensitization is not unique to marijuana. Alcohol and nicotine also prime the brain for a heightened response to other drugs52 and are, like marijuana, also typically used before a person progresses to other, more harmful substances.
It is important to note that other factors besides biological mechanisms, such as a person's social environment, are also critical in a person's risk for drug use. An alternative to the gateway-drug hypothesis is that people who are more vulnerable to drug-taking are simply more likely to start with readily available substances such as marijuana, tobacco, or alcohol, and their subsequent social interactions with others who use drugs increases their chances of trying other drugs. Further research is needed to explore this question.
What are marijuana's long-term effects on the brain?
Substantial evidence from animal research and a growing number of studies in humans indicate that marijuana exposure during development can cause long-term or possibly permanent adverse changes in the brain. Rats exposed to THC before birth, soon after birth, or during adolescence show notable problems with specific learning and memory tasks later in life.32-34 Cognitive impairments in adult rats exposed to THC during adolescence are associated with structural and functional changes in the hippocampus.35-37 Studies in rats also show that adolescent exposure to THC is associated with an altered reward system, increasing the likelihood that an animal will self-administer other drugs (e.g., heroin) when given an opportunity (see "Is marijuana a gateway drug?").
Imaging studies of marijuana's impact on brain structure in humans have shown conflicting results. Some studies suggest regular marijuana use in adolescence is associated with altered connectivity and reduced volume of specific brain regions involved in a broad range of executive functions such as memory, learning, and impulse control compared to people who do not use.38,39 Other studies have not found significant structural differences between the brains of people who do and do not use the drug.40
Several studies, including two large longitudinal studies, suggest that marijuana use can cause functional impairment in cognitive abilities but that the degree and/or duration of the impairment depends on the age when a person began using and how much and how long he or she used.41
Among nearly 4,000 young adults in the Coronary Artery Risk Development in Young Adults study tracked over a 25-year period until mid-adulthood, cumulative lifetime exposure to marijuana was associated with lower scores on a test of verbal memory but did not affect other cognitive abilities such as processing speed or executive function. The effect was sizeable and significant even after eliminating those involved with current use and after adjusting for confounding factors such as demographic factors, other drug and alcohol use, and other psychiatric conditions such as depression.42
A large longitudinal study in New Zealand found that persistent marijuana use disorder with frequent use starting in adolescence was associated with a loss of an average of 6 or up to 8 IQ points measured in mid-adulthood.43 Significantly, in that study, those who used marijuana heavily as teenagers and quit using as adults did not recover the lost IQ points. People who only began using marijuana heavily in adulthood did not lose IQ points. These results suggest that marijuana has its strongest long-term impact on young people whose brains are still busy building new connections and maturing in other ways. The endocannabinoid system is known to play an important role in the proper formation of synapses (the connections between neurons) during early brain development, and a similar role has been proposed for the refinement of neural connections during adolescence. If the long-term effects of marijuana use on cognitive functioning or IQ are upheld by future research, this may be one avenue by which marijuana use during adolescence produces its long-term effects.44
However, recent results from two prospective longitudinal twin studies did not support a causal relationship between marijuana use and IQ loss. Those who used marijuana did show a significant decline in verbal ability (equivalent to 4 IQ points) and in general knowledge between the preteen years (ages 9 to 12, before use) and late adolescence/early adulthood (ages 17 to 20). However, at the start of the study, those who would use in the future already had lower scores on these measures than those who would not use in the future, and no predictable difference was found between twins when one used marijuana and one did not. This suggests that observed IQ declines, at least across adolescence, may be caused by shared familial factors (e.g., genetics, family environment), not by marijuana use itself.45 It should be noted, though, that these studies were shorter in duration than the New Zealand study and did not explore the impact of the dose of marijuana (i.e., heavy use) or the development of a cannabis use disorder; this may have masked a dose- or diagnosis-dependent effect.
The ability to draw definitive conclusions about marijuana's long-term impact on the human brain from past studies is often limited by the fact that study participants use multiple substances, and there is often limited data about the participants' health or mental functioning prior to the study. Over the next decade, the National Institutes of Health is funding the Adolescent Brain Cognitive Development (ABCD) study-a major longitudinal study that will track a large sample of young Americans from late childhood (before first use of drugs) to early adulthood. The study will use neuroimaging and other advanced tools to clarify precisely how and to what extent marijuana and other substances, alone and in combination, affect adolescent brain development.
Marijuana, Memory, and the Hippocampus
mage by the NIDA
Distribution of cannabinoid receptors in the rat brain. Brain image reveals high levels (shown in orange and yellow) of cannabinoid receptors in many areas, including the cortex, hippocampus, cerebellum, and nucleus accumbens (ventral striatum).
Memory impairment from marijuana use occurs because THC alters how the hippocampus, a brain area responsible for memory formation, processes information. Most of the evidence supporting this assertion comes from animal studies. For example, rats exposed to THC in utero, soon after birth, or during adolescence, show notable problems with specific learning/memory tasks later in life. Moreover, cognitive impairment in adult rats is associated with structural and functional changes in the hippocampus from THC exposure during adolescence.
As people age, they lose neurons in the hippocampus, which decreases their ability to learn new information. Chronic THC exposure may hasten age-related loss of hippocampal neurons. In one study, rats exposed to THC every day for 8 months (approximately 30 percent of their lifespan) showed a level of nerve cell loss at 11 to 12 months of age that equaled that of unexposed animals twice their age.
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