CATR: Please tell us about your work.

Dr. Walker: I’m a research professor at the University of Washington in the School of Social Work. I’m a clinical psychologist by training, and a large portion of my research focuses on cannabis use disorder (CUD) treatment.

CATR: Let’s start by clarifying the term “cannabis.”

Dr. Walker: The term cannabis can apply to any product that contains cannabinoids. But when we talk about cannabis here, we are referring to any cannabis plant material, or extract of that material, that contains THC, which is the psychoactive component in cannabis that produces a high. Another compound in cannabis that has garnered a lot of attention, cannabidiol (CBD), does not produce a high and, as far as we know, does not cause addiction or withdrawal. With over 100 cannabinoids present in the cannabis plant, there is still a lot to learn, but as far as we know, THC is the culprit responsible for CUD and withdrawal.

CATR: Can you define CUD? How does it compare with addiction to other substances?

Dr. Walker: CUD is problematic cannabis use that is persistent in the face of negative consequences. Those can be social consequences or negative impacts on physical or mental health. The criteria are really no different than for other substance use disorders (SUDs) such as alcohol, nicotine, cocaine, or opioid use.

CATR: My impression is that because CUD is associated with lower morbidity and mortality than, say, opioid use disorder, many people view cannabis as something not to be taken seriously.

Dr. Walker: Unfortunately, you’re right. A common perception of cannabis is that you can’t actually become addicted to it. We hear that all the time, even sometimes from medical professionals. But cannabis certainly can be addictive, and the research bears that out. It’s important to check our social perceptions because it’s easy to be sucked into whatever opinions are currently popular or reported in the media; those opinions might be widely held, but they are not necessarily scientifically informed. But just like other drugs, people can use cannabis occasionally without significant consequences and without developing an SUD. Figures vary, but as many as 30% of people who use cannabis develop CUD (Hasin DS et al, JAMA Psychiatry 2015;72(12):1235–1242). Of course, prevalence goes up for folks who use larger amounts, use more frequently, and have a younger age of first use (Millar SR et al, BMC Public Health 2021;21(1):997).

CATR: What risk factors put someone at risk of developing CUD?

Dr. Walker: Risk factors for CUD are similar to other addictive substances and include social, psychological, and biological factors. Level of THC exposure is a significant factor; greater frequency of use and higher THC concentration are both associated with the development of CUD. It’s the same as with any other drug—the more your brain is exposed, the more opportunities there are to experience rewarding effects over time, potentially leading to addiction. Another risk factor is comorbid psychiatric illness. That includes other SUDs, psychosis, mood disorders, anxiety, and PTSD. Folks with these diagnoses all have higher rates of CUD than the general population (Borodovsky JT and Budney AJ, Int Rev Psychiatry 2018;30(3):183–202). Finally, people who primarily use cannabis to cope with painful or unpleasant emotions seem to be at greater risk for developing CUD. This pattern of use also tends to be particularly challenging to treat.

CATR: And yet, cannabis is approved for the treatment of many of the conditions you just named, at least in some states.

Dr. Walker: You’re right. It’s important to understand that authorization for medicinal cannabis comes from state legislators, not medical experts. Lawmakers typically get input from researchers, clinicians, and their constituents, but what they do with that information is up to them. So the presence of cannabis on a list of approved “treatments” does not mean that there is an evidence base to suggest that it is actually helpful. In the case of psychiatric illness, regardless of whether the CUD starts before the mental health disorder or vice versa, the two together lead to worse outcomes for the mental health disorder and the CUD. And controlled clinical studies have not found cannabis to be an effective treatment for any psychiatric disorder.

CATR: This situation really leads us to question the term “medical” cannabis, which is used all the time.

Dr. Walker: That’s true; “medical” cannabis is a misnomer. And beyond that, the more you study cannabis, the more you realize how much blurriness there is between “medical” versus “recreational” use. In reality, people don’t separate into tidy categories of using cannabis completely for the treatment of some condition or completely recreationally. We notice that most of the people who use cannabis for the purposes of treatment also sometimes use it to get high, to relax, to have fun. And the same goes for folks who are using cannabis in a recreational way; they might also be using it to cope with unpleasant emotions, or anxiety, or to help them sleep. So using these two terms creates a false sense of two dichotomous categories, when in fact the boundaries are messy. When talking with patients about their cannabis use, it’s important to get a good picture of their reasons for use, the quantity and frequency of their use, and their preferred product’s potency and active compound distribution (THC to CBD ratio) to help understand whether their cannabis use is problematic or risky. (Editor’s note: See the article “Currently Available Cannabis Products” in this issue to learn more about what products are on the market today.)

CATR: Given how commonly cannabis is used, how should providers be on the lookout for CUD? Would you recommend universal screening for all patients in psychiatric treatment?

Dr. Walker: I recommend urine screening for all vulnerable populations: adolescents, pregnant women, patients with psychosis and other mental health problems. I don’t see a downside to universal screening as long as there is sufficient time and resources. I would certainly recommend that all patients are at least asked about cannabis use. And for anyone using cannabis more than once a week, I would recommend a more detailed assessment for CUD.

CATR: How should we screen for CUD?

Dr. Walker: Start by asking, “How often and how much are you using?” Weekly use or more places a patient in a higher normative bracket that elevates the likelihood of CUD. Screening tools are often based on tests for alcohol use. There’s a cannabis version of the Alcohol Use Disorders Identification Test (AUDIT) called the Cannabis Use Disorders Identification Test (CUDIT; www.tinyurl.com/yc3ujnkh). There is also the cannabis version of the Michigan Alcoholism Screening Test (MAST) called the Cannabis Abuse Screening Test (CAST; www.tinyurl.com/s5svdush). These screens are typically easy to use and can be quickly deployed in a busy clinical setting.

CATR: Let’s shift the focus to cannabis withdrawal. What does it look like?

Dr. Walker: Cannabis withdrawal was added when the DSM went from version 4 to version 5 in 2013, so officially at least, it’s a relatively new clinical entity. Symptoms usually start 24–48 hours after cessation of use. Cannabis withdrawal can last up to two weeks, so the time course is quite long. The intensity of symptoms is not as severe as something like alcohol or opioid withdrawal, though—it looks a lot like nicotine withdrawal. There is irritability, anger or aggression, loss of appetite, nervousness, insomnia, weird dreams, restlessness, and depressed mood. Physical symptoms can occur as well, like sweating, fever, chills, shakiness, tremors, and gastrointestinal discomfort. It looks very similar to acute anxiety, which can make differential diagnosis tricky.

CATR: How heavy of a user does someone have to be in order to develop a withdrawal syndrome?

Dr. Walker: That’s not really known, and it probably varies by individual, so I can’t give you a number of days of use or a specific quantity or frequency. But we do know that about 12%–17% of cannabis users have experienced withdrawal in the past year (Livne O et al, Drug Alcohol Depend 2019;195:170–177). It’s quite common, so I don’t think that only heavy daily users experience it, though rates of cannabis withdrawal certainly increase with heavier use. Among people who present for CUD treatment, 50%–75% of them endorse a history of withdrawal symptoms (Bahji A et al, JAMA Netw Open 2020;3(4):e202370). And it can be a big barrier to treatment. It’s one of the main things that people point to when treatment is unsuccessful.

CATR: How is cannabis withdrawal treated?

Dr. Walker: First is to reassure the patient that withdrawal symptoms are not life-threatening. Often the treatment is just psychoeducation—“This is what to expect, this is the time course, this is what you could experience in the next week or two, and it will go away if you don’t use.” There doesn’t need to be any type of specialized detox, just some good social support, good psychoeducation, and reassurance. I recommend that patients try to get plenty of sleep, take hot baths or showers, eat healthy food, get exercise—activities that might help address specific symptoms of withdrawal. Medications have been tried to treat withdrawal symptoms such as sleep disturbance. There has been interest in cannabinoid receptor agonists (dronabinol or nabiximols), and they do appear to reduce symptoms of withdrawal. If a patient reports that severe withdrawal symptoms have thwarted a CUD treatment attempt in the past, they might be good candidates for these medications, though they aren’t used commonly.

CATR: And what treatments do we have to offer once a patient makes it through withdrawal?

Dr. Walker: While we do have treatments for CUD, the literature is not as robust as you might hope. CUD research really didn’t start until the late 1980s, and research paradigms have been largely based upon those from alcohol research. The three treatment modalities with the most empirical support are cognitive behavioral therapy (CBT), motivational enhancement therapy (MET), and contingency management (CM). For adolescents, you could add family therapy as well.

CATR: How can our readers learn more about the specifics of these therapies?

Dr. Walker: The principles employed in therapy for CUD are similar to treatment for other addictions or mental health conditions. But if readers are looking for specific resources, I would point them to a free online manual, developed for a multisite trial done in the late 1990s, that combines MET and CBT techniques (www.tinyurl.com/3bsdyaz8; Marijuana Treatment Project Research Group, J Consult Clin Psychol 2004;72(3):455–466). There are study manuals available for those working with adolescents as well. In fact, our group makes our manuals for MET available online (www.tinyurl.com/36r34psj).

CATR: And how do synthetic cannabinoids fit into all of this?

Dr. Walker: Synthetic cannabinoids are quite different; these are artificial drugs that act on the same brain receptors as THC, but they are different chemicals. These drugs evolve and change rapidly, making them difficult to test for. They are widely available, often sold at convenience stores or online. They bind to cannabinoid receptors, like natural cannabis, but the potency is much higher—they just overload the receptors. And the subjective experience of using them is pretty different than with natural cannabis. We see much higher rates of delusions and hallucinations, severe anxiety, and more physical symptoms such as racing heart, vomiting, and breathing problems. But synthetic cannabinoids are a relatively recent development that we just don’t know much about. For example, even as a cannabis researcher, I didn’t learn about them until 2008. I was conducting a military study for alcohol and our soldiers were talking about their use of “spice,” which is a term for synthetic cannabinoids (Walker D et al, Addict Behav 2014;39(7):1139–1144). Nowadays they’re also called “K2,” “spike,” and “fake weed.” That seems to be one of the attractive aspects about synthetic cannabinoids: They are difficult to detect. They appeal to people being drug tested regularly, like military service members or those on probation or parole.

CATR: And did the subjects in your study who used synthetic cannabinoids develop use disorder and withdrawal?

Dr. Walker: Yes, absolutely. Again, the criteria for use disorder from substance to substance are essentially the same: continued use despite negative consequences. In the case of synthetic cannabinoids, the physical symptoms of intoxication and withdrawal were so much more intense than those produced by natural cannabis. In terms of treatment, we don’t have much research done in the field. But I would recommend utilizing the same therapeutic techniques that have been shown to be effective for CUD and other SUDs as well: MET, CBT, and CM when possible.

CATR: Thank you for your time, Dr. Walker.