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Addressing Criticisms of the Disease Model

Volkow, Koob, and McLellan on the neurobiology of addiction.

The New England Journal of Medicine recently published a review article, “Neurobiologic Advances from the Brain Disease Model of Addiction,” authored by three prominent figures in the field of addiction research: Nora Volkow, the director of the National Institute of Drug Abuse (NIDA); George Koob, the director of the National Institute of Alcohol Abuse and Alcoholism (NIAAA); and Thomas McLellan, founder and chairman of the Treatment Research Institute in Philadelphia.  The article summarizes the research that has “increasingly supported the view that addiction is a disease of the brain,” and concludes that “neuroscience continues to support the brain disease model of addiction.”

The implications of this, say the authors, are straightforward: “As is the case in other medical conditions in which voluntary, unhealthful behaviors contribute to disease progression (e.g., heart disease, diabetes, chronic pain, and lung cancer), evidence-based interventions aimed at prevention, along with appropriate health policies, are the most effective ways of changing outcomes.”

And some of the implications are immediate: “A more comprehensive understanding of the brain disease model of addiction many help to moderate some of the moral judgement attached to addictive behaviors and foster more scientific and public health-oriented approaches to prevention and treatment.”

In a supplementary appendix, the authors address some of the common criticisms of the disease model of addiction, and offer counter-arguments. The quotes below are excerpted directly from the appendix.

—Most people with addiction recover without treatment, which is hard to reconcile with the concept of addiction as a chronic disease.

This reflects the fact that the severity of addiction varies, which is clinically significant for it will determine the type and intensity of the intervention. Individuals with a mild to moderate substance use disorder, which corresponds to the majority of cases, might benefit from a brief intervention or recover without treatment whereas most individuals with a severe disorder will require specialized treatment

—Addicted individuals respond to small financial rewards or incentives (contingency management), which is hard to reconcile with the notion that there is loss of control in addiction.

The demonstrated effectiveness of contingency management shows that financial cues and incentives can compete with drug cues and incentives – especially when those financial incentives are significant and relatively immediate; and when control has been simply eroded rather than lost. Contingency management is increasingly being utilized in the management of other medical disorders to incentivize behavioral changes (i.e., compliance with medications, diets, physical activity).

—Gene alleles associated with addiction only weakly predict risk for addiction, which is hard to reconcile with the importance of genetic vulnerabilities in the Brain Disease Model of Addiction.

This phenomenon is typical of complex medical diseases with high heritability rates for which risk alleles predict only a very small percentage of variance in contrast to a much greater influence of environmental factors (i.e., cirrhosis, diabetes, asthma, cardiovascular disease). This reflects, among other things, that the risk alleles mediate the response to the environment; in the case of addiction, the exposures to drugs and stressful environments.

Overlaps in brain abnormalities between people with addiction and control groups raises questions on the role that brain abnormalities have on addiction.

The overlap is likely to reflect the limitation of currently available brain imaging techniques (spatial and temporal resolutions, chemical sensitivity), our limited understanding of how the human brain works, the complexity of the neurobiological changes triggered by drugs and the heterogeneity of substance use disorders.

Treatment benefits associated with the Brain Disease Model of Addiction have not materialized.

Medications are among the most effective interventions for substance use disorders for which they are available (nicotine, alcohol and opiates). Moreover, progress in the approval of new medications for substance use disorders has been slowed by the reluctance of pharmaceutical companies to invest in drug development for addiction.

Benefits to policy have been minimal.

The Brain Disease Model of Addiction provided the basis for patients to be able to receive treatment for their addiction and for insurances to cover for it. This is a monumental advance in health policy. The Brain Disease Model of Addiction also provides key evidence-based science for retaining the drinking age at 21 years.

Cannabis sativa vs. Cannabis indica: Science or Folklore?

Golden Goat or  Sour Diesel?

The bland assurances from medical marijuana dispensaries about the physical and psychological effects of the bewildering array of hybrid plant strains on offer is mostly bunk, claim a growing number of cannabis scientists.

Ethan Russo, a neurologist and pharmacology researcher, as well as the medical director of a biotechnology company, author of numerous books about herbal medicine, and a former faculty member at the University of Washington and the University of Montana, has something to say to marijuana connoisseurs: “There are biochemically distinct strains of Cannabis, but the sativa/indica distinction as commonly applied in the lay literature is total nonsense and an exercise in futility.”

How’s that again? The much-vaunted divide between the cerebral sativa strains, and the sedating, body-oriented effects of indica, are an integral part of marijuana lore and legend. Cannabis growers and biologists endlessly debate the hybridization of new strains. Extolling the virtues of a sativa plant crossed with a plant redolent of indica is a common sales pitch.

In an interview with Dr. Daniele Piomelli for the January 2016 issue of the journal Cannabis and Cannabinoid Research, Russo detailed his disagreement with the assumption that hard evidence exists for this distinction. Dr. Piomelli notes that “sativa is often described as being uplifting and energetic, whereas indica as being relaxing and calming.” Folklore, says Russo. Of course different strains have different effects. But in recent years, says Russo, almost all marijuana has been coming from high-THC strains, with a slight increase in CBD-predominant strains:

"The differences in observed effects in Cannabis are due to their terpenoid content, which is rarely assayed, let alone reported to potential consumers. The sedation of the so-called indica strains is falsely attributed to CBD content when, in fact, CBD is stimulating in low and moderate doses. Rather, sedation in most common Cannabis strains is attributable to their myrcene content, a monoterpene with a strongly sedative couch-lock effect that resembles a narcotic."

And, as for sativa strains: “A high limonene content (common to citrus peels) will be uplifting on mood, while the presence of the relatively rare terpene in Cannabis, alpha-pinene, can effectively reduce or eliminate the short-term memory impairment classically induced by THC.”

Well. I for one do not wish to be caught in the firing line between Dr. Russo and the legions of growers who will beg to differ with his conclusions. For years, it has been accepted wisdom that cannabis comes in two different forms, essentially considered two different species even though they readily interbreed. Even Jean-Baptiste Lamarck, the legendary naturalist of the 18th Century, agreed with the indica and sativa concepts.

But Russo will have none of it: “To paraphrase and expropriate an old Yiddish expression: 12 botanical taxonomists, 25 different opinions…. One cannot in any way currently guess the biochemical content of a given Cannabis plant based on its height, branching, or leaf morphology. The degree of interbreeding/hybridization is such that only a biochemical assay tells a potential consumer or scientist what is really in the plant.”

And finally: “I would strongly encourage the scientific community, the press, and the public to abandon the sativa/indica nomenclature and rather insist that accurate biochemical assays on cannabinoid and terpenoid profiles be available for cannabis in both the medical and recreational markets. Scientific accuracy and the public health demand no less than this.”

Russo’s interview is strong evidence of a viewpoint brought to public attention a few years ago by several others, including the controversial cannabis chemist Jeffrey Raber.

Raber told the L.A. Weekly in 2013 that there was no compelling scientific evidence for the claims routinely made by cannabis dispensaries about the effects of a given colorfully named strain of marijuana. “We took a popular [strain] name, Jack Herer, and found that most didn’t even look like each other. OG whatever, Kush whatever, and the marketing that goes along with it—it’s not really medically designed.”

And the difference between sativa and indica? The cerebral, bracing “mental” high vs. the sleepy, couch-lock “body” high? Forget it, said Raber. The two sub-species are distinguished by morphology only—different structures and appearance, but no hard and fast rules about the quality of the smoking experience. They look different, but that’s no guide to the distribution of THC, CBD, and numerous terpenes that determine the actual quality of the marijuana experience. Moreover, extensive crossbreeding by growers and dealers has helped to obliterate any consistent, meaningful distinctions between sativa and indica highs. (The so-called “skunk” varieties are simply high quality female plants that are prevented from going to seed, which dramatically pushes up the THC content. Almost all of the high-quality weed sold in the U.S., Canada, and the U.K. is skunkweed, so the definition is virtually useless.)

Sativa plants are characteristically tall and rangy, with long branches and long, thin leaves. They evolved, scientists believe, in humid jungle climates. Indica plants are shorter, more compact, and stubbier-looking, with shorter branches and fatter leaves designed for a hot, desert-like climate. It has been assumed that sativas originally came from India, and indicas from Afghanistan. However, indica is the term meant to indicate a plant from India, so right away we find that the situation is all muddled up: the plant from Afghanistan is known by the name of the plant from India. Blame this one on esteemed plant drug investigator Richard Evans Schultes, who apparently mislabeled the plants grown in Afghanistan as C. indica when he drew up the first cannabis taxonomy in the 1970s.

It gets worse. In 2014, at a meeting of the International Cannabis Research Society, research John McPartland with GW Pharmaceuticals announced  the results of his study of genetic markers on the three subspecies of cannabis: C. sativa, C. indica, and a third wild variety, known as C. ruderalis, with very little THC. Any of the three subspecies can be bred as hemp or marijuana, said McPartland. Cannabis sativa should really be known as Cannabis indica, being the Indian variety, while the formerly misnamed indica subspecies should now be called Cannabis afghanica. The name of C. sativa, the high-end connoisseur favorite, would now go to the lowly C. ruderalis, otherwise known as ditch weed, under his new classification scheme.

Quite a lot of changes to a decades-old nomenclature, but it means we are finally getting some serious genetic information about one of the most popular drugs in the world. As Jeremy Daw of The Leaf Online writes: “Starbucks, for example, sources coffee beans from farmers spread across four continents…. In an astonishing feat of global supply chain logistics, Starbucks can now claim to have the ability to trace 94% of its coffee beans all the way back to the exact farm where they were produced.” The cannabis industry, he concludes, still has “a lot of growing up to do.”

Krymon deCesare, chief research director at Steep Hill Halent Lab in Oakland, California, a company developing more sophisticated tests for identifying the various compounds found in marijuana, told AlterNet  that “sativa and indica are only really valid for describing the physical characteristics of the cannabis strain in a given environment. They are not nearly as reliable as terms for making assumptions about energy versus couch lock.” To the extent that there is a grain of truth in the basic division between the mind high of sativa and the body high of indica, as traditionally classified, deCesare believes the culprit is myrcene. Based on the analysis of more than 100,000 samples, deCesare says that his team found “consistently elevated levels of the terpenoid myrcene in C. indica as compared to C. sativa. Myrcene is the major ingredient responsible for ‘flipping’ the normal energetic effect of THC….”

Ethan Russo invokes his notion of the “entourage effect,” in which the distinctive highs normally associated with indica and sativa are in fact the result of a complex combination of many different cannabinoids and terpenes working in harmony. Teasing that apart in the lab is not a cheap or easy affair. If you don’t know your terpene levels, says Russo, than you can’t compute your relative chances of full couch-lock. And even if terpene levels are known, the same pot plant, when smoked, can still cause one person to become energized and talkative, while another person may just fall asleep. Same chemicals, different metabolisms. One person’s happy, giggly high is another person’s paranoid bad trip.

The result of this recent research is to bolster the general suspicion about medical marijuana dispensaries: The names of various marijuana varieties are not only stupid and immature, but also completely misleading and unhelpful. Coherent labeling will require much more than listing relative THC percentages. We’ve only just begun.

A Roundtable Discussion on Cannabis Use Disorder

Addressing the habit-forming aspects of marijuana.

A trio of leading marijuana scientists participated in a panel discussion moderated by Dr. Daniele Piomelli from the School of Medicine at the University of California-Irvine, and published in a recent issue of the journal Cannabis and Cannabinoid Research.

Dr. Margaret Haney is with the New York State Psychiatric Institute at Columbia University Medical Center; Dr. Alan J. Budney is affiliated with the Geisel School of Medicine at Dartmouth College; and Dr. Pier Vincenzo Piazza works at the Magendie Neurocenter in Bordeaux, France.

Excerpts from the long discussion appear below:

It seems that most specialists in the field agree that Cannabis is addictive. If you had to choose one piece of evidence, either clinical evidence or animal experiment evidence, in support of this conclusion, which one would you pick?

Dr. Margaret Haney: “One of the key features for me is demonstrating that there is a pharmacologically specific withdrawal from Cannabis use…. We can demonstrate that daily smokers go through a time-dependent and pharmacologically specific withdrawal when they abstain from Cannabis…. I think another really important feature is the clinical data showing how high relapse rates are with Cannabis. Although Cannabis may have a lower abuse liability than other drugs like cocaine or nicotine, once somebody has developed a dependence on the drug, then quitting becomes extremely difficult.

Dr. Alan J. Budney: “If I had to pick out the ‘smoking gun’ to convince the public and the scientific world that Cannabis Use Disorder (CUD) is real, then it would be the data from clinical epidemiological research…. the data on CUDs are remarkably similar to the other substance use disorders…. for a substantial number of people, Cannabis use causes similar and substantial problems that are comparable to other types of drugs that we all agree have addictive potential.”

Dr. Pier Vincenzo Piazza: “[In] Australia, Canada, the United States, and the European Union, over the last two years Cannabis represents the highest new entries for treatment in specialized centers…. Since these four countries have very different rates of referral of patients by the judicial system, these figures really mean that patients experience a discomfort high enough to spontaneously seek treatment…. In France, for example, as well as in many other European countries, referral from the judicial system is very low. Nevertheless, the demand for treatment for CUD is now the highest of all drugs, legal and illegal.”

What is curious is that we now accept the concept that Cannabis is addictive, but for many years we have been told that it was not. Why is it that, for so long, the scientific community failed to recognize the addictive properties of Cannabis?

Dr. Margaret Haney: “I have been speaking about Cannabis addiction for 20 years and was met by full-on boredom for the first 15 years because I felt that scientists, like the public at large, just viewed Cannabis as a benign compound not too different from caffeine in a way…. THC is lipophilic, and so long-lasting, withdrawal takes quite a while to manifest…. if an individual is dependent on nicotine, he or she cannot go a couple of hours without experiencing withdrawal. A heavy Cannabis user, by contrast, has to go quite a while before experiencing withdrawal, and so it was not quite as obvious to people that withdrawal existed.”

Dr. Alan J. Budney: “Moreover, many of those that have experience with using Cannabis, do not get addicted, develop problems, or experience withdrawal. Although the same is true for those who have used alcohol or even opiates, for reasons that are not completely clear, the personal experience of those who used Cannabis and did not develop problems or experience withdrawal, seems to lead to the perception that Cannabis is not a substance that others can become addicted to.”

Dr. Pier Vincenzo Piazza: “What we know now is that, since cannabidiol is an antagonist of THC, the greater the ratio between THC and cannabidiol the greater the risk for Cannabis to be addictive…. Now, we are up to a 5- to 10-fold difference in favor of THC, making Cannabis more addictive.”

How addictive is Cannabis? Is it more addictive than, say, tobacco or alcohol? Is it less addictive? Is this question even correctly asked? Is there a better way to ask it?

Dr. Alan J. Budney: [I] would like to emphasize a point so that our audience does not think we are going way overboard and engaging in reefer madness related to the severity of Cannabis addiction. All factors held constant, the pharmacology of opiates would probably produce a more severe addiction…. Access, dose, route of administration, societal acceptance, perceived risk, cost, societal consequences for use or intoxication, and multiple other factors contribute to the real-world question of how addictive a drug is compared to another.”

Dr. Margaret Haney: “My opinion is that Cannabis has a lower abuse liability than something like cocaine [but] even if Cannabis has a lower abuse liability, the sheer number of people using it will result in a large number of people with a use disorder….”

Dr. Pier Vincenzo Piazza: “If we try to express abuse liability in numbers, the abuse liability for Cannabis… is between 10% and 15%, depending on the survey you look at. However, I believe that abuse liability should also be measured by a second factor; that is, how easy it is to quit if you have developed a substance use disorder. My understanding… is that stopping Cannabis use, if you have developed CUD, is not easier than other drugs.”

The major point, all three experts agree, is that marijuana cannot be considered a completely benign drug. “Cannabis is not the worst drug,” says Dr. Haney, “but it is not a drug without consequences. Again, societal attitudes often seem to skew one way or the other; it is all good or it is all bad, when it is clearly both.”

Graphics Credit: hhttp://moodsurfing.com

Annual NIDA Survey Shows Declines in Teen Drug Use

The kids are all right.

Every year, the National Institute of Drug Abuse (NIDA), under the auspices of the National Institutes of Health, conducts its Monitoring the Future survey of drug use among American young people in the 8th, 10th, and 12th grades.

This year, students got very good marks. “We are heartened to see that most illicit drug use is not increasing, non-medical use of prescription opioids is decreasing, and there is improvement in alcohol and cigarette use rates,” said Dr. Nora Volkow, Director of NIDA.

Here are some highlights from this year’s study:

— Despite nationwide concerns over prescription opioid and heroin abuse, heroin use among students has hit historic lows, while “narcotics other than heroin” continue to decline as well. Only 4.4% of high school seniors reported Vicodin use in the past year, compared to more than 10% in 2003.

—The downward trend in teen cigarette smoking continues, and is presently at the lowest rate in the study’s history. 5.5% of high school seniors had smoked, compared to 10.7% in 2010. The highest rate of smoking recorded among seniors was 25% in 1997. Among 10th graders, daily smoking has been cut in half in the past five years, down to 3%.

—For the first time since the annual study began, marijuana use exceeds cigarette use among 12th graders. 35% of high school seniors reported past-year cannabis use, and 6% reported daily use. (Daily use of cigarettes was 5.5%). Disapproval rates concerning regular smoking have continued to rise, even as the disapproval rates concerning marijuana risk continue to fall among teens.

—Alcohol use continues its slow but steady downward trend among teens, “with significant reductions seen in the past five years in nearly all measures.” However, it remains the most commonly used drug, 58% of seniors having used it in the past year.

—Synthetic marijuana, the class of Spice/K2/herbal incense drugs, continues to decline in popularity, presumably due to fears about adverse side effects.

—16% of 12th graders reported using e-cigarettes in the past month, although only one out of five student users said they were vaping nicotine. 13% of 8th graders said they had no idea what was in the e-cigarette device they were using. Other answers ranged from flavorings to marijuana.

The Great Gateway Theory

Smoke pot, shoot smack?

The Great Gateway Hypothesis has had a long, controversial run as a central tenet of American anti-drug campaigns. As put forth by Denise B. Kandell of Columbia University and others in 1975, and refined and redefined ever since, the gateway theory essentially posits that soft drugs like alcohol, cigarettes, and marijuana—particularly marijuana—make users more likely to graduate to hard drugs like cocaine and heroin. What is implied is that gateway drugs cause users to move to harder drugs, by some unknown mechanism. The gateway theory forms part of the backbone of the War on Drugs. By staying tough on marijuana use, policy makers believe they will have much broader impacts on hard drug use down the road.

This notion is virtually an article of faith in the drug prevention community. It just feels intuitively right: Scratch a junkie, and you’ll find a younger, embryonic pot smoker or furtive teenage drinker. Ergo, prevent teen pot smoking, and you will block the blossoming of a multitude of future hard drug addicts.

For years, the gateway hypothesis has had its share of contentious opponents. The countervailing theory is known primarily as CLA, for Common Liability to Addiction, the genetically based approach that lines up with the notion of addiction as a chronic disease entity. Most genetic association studies have failed to record risk variations for addiction that are specific to one addictive drug. Writing in 2012 in Drug and Alcohol Dependence, Michael M. Vanyukov of the University of Pittsburgh, along with a large group of prominent addiction researchers, argued that the gateway hypothesis is essentially a form of circular reasoning. “It is drug use itself that is viewed as the cause of drug use development,” they write. The staged progression from one drug to another “is defined in a circular manner: a stage is said to be reached when a certain drug is used, but this drug is supposed to be used only upon reaching this stage. In other words, the stage both is identified by the drug and identifies the drug. In effect, the drug is identical to the stage.”

The researchers reject any causal claims on behalf of the gateway hypothesis and insist there is no necessary usage of soft drugs at an earlier stage to pave the way for hardcore addiction, however watertight the idea might sound. The high correlations are “artifactual,” they argue, “because they are estimated among hard drug users, without taking into account the large population of those who try or even habitually use marijuana but never transition to harder drugs.” A common cause, such as an underlying vulnerability to all drugs of abuse, seems more to the point, they insist. There is nothing out there to suggest that “these stages are either obligatory or universal, nor that all persons must progress through each in turn… the initiation order is frequently reversed even for the licit-to-illicit sequence.” There is only one stage that universally precedes hard drug use, they argue. And that is non-use. “It is the non-use then, which should be the actual gateway condition.”

The leading theory supporting the gateway hypothesis is that some as yet undetermined mechanism of “sensitization” occurs after using a gateway drug. But there is no science supporting this notion. “If sensitization does occur,” the researchers say, “it is equivalent to an increase in individual liability at the level of neurochemical mechanisms of addiction.”

The paper in Drug and Alcohol Dependence notes that in Japan, where marijuana is used by less than 5 percent of young people, “cannabis is not used first by a staggering 83.2% of the users of other illicit drugs, thus violating the gateway sequence.” Japan also handily knocks down the idea of alcohol as a gateway drug: Whereas the prevalence of aldehyde dehydrogenase deficiency—the so-called alcohol flush reaction—keeps many Asians from drinking alcohol regularly, this does not correlate with lower rates of non-alcohol substance use in that population.

All of this would seem to put the last nail in the notion that “involvement in various classes of drugs is not opportunistic but follows definite pathways,” as Vanyukov et. al. put it. Common sense seems to be ahead of official drug policy in this regard.

For proponents of common liability to addiction models, any staged sequencing of drug use is considered opportunistic and trivial. Which, interestingly, is how many addicts tend to view the gateway theory. But the idea of marijuana or alcohol as a gateway drug just feels intuitively correct to many people. Part of the problem is chronological. “At the relatively distal time when genetic relationships are usually evaluated,” the authors maintain, “the role of this early-acting factor may be as difficult to detect as it is to find a match that started a forest fire.” Your genetic endowment is with you from birth, while your first drink or toke of marijuana does not happen for a decade or two. Individual environmental conditions, from epigenetic changes to a move to a different neighborhood, determine how it will play out down the road, but these factors are mostly invisible at the time of addiction.

All of this matters from a policy point of view, because research “may be hindered or misdirected if a concept lacking substance, validity and utility is accorded prominence.” However, even when the gateway hypothesis is taken as a given, different legal and social outcomes are still possible. The best example is found in The Netherlands. The prevailing belief there is that “the pharmacological effects of cannabis increase adolescents’ likelihood of using other drugs,” as stated  by Wayne Hall, a professor of public health policy at the University of Queensland, Australia. Writing in Addiction, Hall says that drug policy analysts in The Netherlands have argued that the fabled gateway “is a consequence of the fact that cannabis and other illicit drugs are sold in the same black market; they have advocated for the decriminalization of cannabis use and small retail sales in order to break the nexus between cannabis use and the use of other illicit drugs.”

This “Marijuana Shop” approach may have direct relevance in the U.S., in the wake of cannabis legalization in Washington and Colorado. James Anthony, a professor of epidemiology at the Bloomberg School of Public Health at Johns Hopkins, writes about the real-world ramifications of the cannabis shop in Addiction: “Do we actually achieve a near-term delay in the time to a young person’s first chance to try cocaine or heroin... [or] do we run the risk of accumulating more cases of dependence on marijuana, or other hazards attributable to non-essential marijuana use?

The true gateways to addiction appear to be behavioral. As part of their genetic endowment, budding addicts are far more likely than other people to exhibit behavioral “dysregulation” when young, in the form of disinhibition, impulsivity, and antisocial behaviors. More than half of all addicts are co-morbid, meaning they also have a psychological or behavioral disorder in addition to addiction. Further analysis of this fact would seem to be a more fruitful research avenue than simply prodding at alcohol or marijuana in an effort to uncover their chemical “secrets” for compelling future drug use.

First published April 14, 2013.