Q&A with Marijuana expert Dr. Kevin Hill

You are here

Kevin Hill, MD, MPH, marijuana expert and author of Marijuana: The Unbiased Truth, answered your questions as a Network of Practice Featured Researcher. See the Q&A below.

Watch a video of his iTraining webinar on the ATTC Vimeo site.

Addiction/Dependency

1. Will there be an increase with addiction as marijuana becomes legal throughout the US?
At this point, we don’t know if we will see increases in marijuana addiction as more states legalize the recreational use of marijuana. In my opinion, this will depend on many factors, including how well we educate people about the science of marijuana as well as how well the regulations are written. While many feel that there will be an increase in addiction as a result of legalization, it should be noted that an important research study was published on June 17 in Lancet Psychiatry that showed that states with medical marijuana laws did have an increase in addiction among young people when compared to states without medical marijuana laws. Sometimes we think we know what will happen, but reality can be different.

 

2. Dr. Hill, in your webinar, are you saying that those that are not a part of the 9% cannot ever get addicted. If they are using daily, is that not an addiction?
Anyone can become addicted, although some are at greater risk than others. A person with addiction in their family is at higher risk, for example. In the webinar, I cited statistics that show that 9% of adult users of marijuana become addicted. Can someone use marijuana and not be addicted? It is possible, but not likely. Any time someone is using daily and cannot skip a day or more without difficulty, it is worth a closer look (perhaps through an evaluation with a mental health professional) to determine if they are in fact addicted.

 

3. Are you aware of the demographics around use and addiction?
Addiction does not discriminate. It affects all ages, genders, and ethnicities. At times, people from certain communities may think that addiction happens only in other communities that may be less affluent or not as close-knit. But the evidence is clear, addiction is everywhere, so we all must be able to recognize it and respond to it. I see all types of patients from a variety of communities and I speak at schools in the city and in the suburbs. At their core, many of the stories of addiction are very similar.

 

4. On the slide for dependence among users, the data is being culled from 1994. Is there updated data available on usage and dependence?
Yes, one source of such information, at least for adult usage and dependence statistics, is the research by Dr. Lopez-Quintero (2011) and his colleagues. Looks like I need to make some new slides.

 

Adolescence

1. Does alcohol addiction in young people compare similarly to marijuana and young people?
Alcohol and marijuana addiction are similar in some ways and different in others. With each, a young person can have problems acutely, or on one day alone, if their judgment is impaired. They may make decisions they would not otherwise make while under the influence of alcohol or marijuana, or they may, for example, have a run in with the law either by using in a public place of using before driving. Chronic use—use daily or nearly every day—can affect the brain or worsen certain psychiatric conditions like ADHD, anxiety, or depression. One difference is in use patterns. Young people often “binge drink” or have many alcoholic drinks in a matter of hours and become extremely intoxicated. This is seen less with marijuana use.

 

2. How long does addiction last for adolescents?
This is an excellent question. First, it is worth pointing out that young people may experience problems associated with using a substance like marijuana without being addicted. If a young person is using marijuana in a car with their friends and they get pulled over by the police, that becomes an issue. Addiction can be defined several ways. A simple definition is “repeated use despite harm”; the American Psychiatric Association defines addiction in its Diagnostic and Statistical Manuals with several criteria that include the need to use more and more drug to get the same effect, withdrawal symptoms when someone stops abruptly, and spending considerable time and effort to use a drug, usually at the expense of other responsibilities. Addiction is a chronic medical condition like asthma, diabetes, or high blood pressure. So if someone meets criteria for addiction, addiction should be a lifelong concern for them. They very well may be able to manage it so they can function normally, but they will always be at risk for relapse.

 

3. Is the percent of people who begin using marijuana on a frequent basis in adolescence result in a similar rate of addiction as when an adolescent uses alcohol on a frequent basis?
One in six young users of marijuana will develop addiction. The National Institute on Alcohol Abuse and Alcoholism (NIAAA) reports that, in the United States, 697,000 adolescents meet criteria for alcohol use disorder. Once you start using either marijuana or alcohol frequently, the chances of developing an addiction increase. In those young people—who are already using frequently—the percent developing addiction is likely similar.

 

Effects on the body

1. What kind of damage is done within the lungs, and or connection to cancer, from inhaling heavy amounts of thick smoke and the large amounts of residue deposited in the system?
This is an excellent question and one that comes up often when I give talks about marijuana use. Smoking any substance, whether marijuana or tobacco, is not good for the lungs. The risks of cigarette smoking, including the increased likelihood of developing lung cancer, are well documented, which is one reason that cigarette use has sharply declined in recent years.

Smoking marijuana increases respiratory infections as well as the likelihood that a person will develop chronic bronchitis. Marijuana smoke contains toxins and carcinogens just like tobacco smoke. However, research has yet to show a link between marijuana use and lung cancer.

 

2. What level of THC impairs a person’s functioning ( i.e., driving)?
Marijuana affects driving performance, but it does it in a different way than alcohol does—it causes different types of errors. The level of THC that impairs driving depends on the person—their body type and their experience with marijuana. Higher levels of THC are required to impair experienced users than inexperienced users. A recent study by Dr. Marilyn Huestis’ group suggested that .13 µg/L THC is equivalent to .08 blood alcohol content. The problem is that marijuana and alcohol are processed differently by the body. As a result, levels of THC do not correlate as well as blood alcohol content in assessing impairment.

 

3. Is there a link between marijuana use and heart disease?
Marijuana use is associated with certain vascular changes that increase risk for heart attack and stroke while someone is under the influence of marijuana.

 

4. Concerning the workplace, for employees with THC in their systems, what are the risk to self or others particularly in safety sensitive positions?
As with the driving question above, it is important to point out that having THC in the blood does not mean that someone is under the influence of THC or impaired. Performing work-related tasks, especially in safety-sensitive positions, under the influence of marijuana increases the risk for bad outcomes.

 

5. We've heard about links to breast/testicular cancer with marijuana use. Do these links exist, or is the research still pending on those as well?
There are at least three studies that show that marijuana use increases the risk for testicular cancer. This association appears to increase with the level of use. Importantly, these studies do not show that marijuana use causes testicular cancer, it is associated with it. I am not aware of any studies linking marijuana to breast cancer. If you know of references, please post here.

 

6. What impact does long term use of marijuana have on memory?
Long-term daily use of marijuana appears to affect memory and other important brain functions. Imaging studies suggest that such long-term use causes structural changes in the brain, and a long-term study by Meier et al. 2012 showed that long-term users who started in their teens and continued for years lost up to 8 points in IQ over time. Of course, short-term memory can be affected while under the influence of marijuana as well.

 

Medical Marijuana

1. Please address how THC and CBD levels are considered when defining medical marijuana.
The major difference between medical marijuana and recreational marijuana is where you buy it—medical marijuana is purchased at dispensaries and recreational marijuana may be purchased “on the street” or at stores in states with legalized recreational marijuana. Otherwise, they may not be any differences between medical and recreational marijuana. Medical marijuana is more likely to be high quality or “high grade” marijuana because it is usually grown using the latest and best technology.

THC and CBD are only two of over 60 cannabinoids found in the marijuana plant. THC is psychoactive, so it accounts for the “high” feeling, but it has other properties as well—for example, it can be anti-inflammatory or it can cause feelings of psychosis. CBD is not psychoactive and it may reduce anxiety or psychotic symptoms. Additional studies are uncovering other medical purposes for these cannabinoids. In early clinical trials, for example, CBD shows promise as a treatment for pediatric epilepsy.

THC and CBD can be adjusted in a 1:1 ratio for the most part. Increase the concentration of THC in a marijuana variety and the CBD concentration decreases. Strains, or varieties, of medical marijuana are thought to have different medical value based upon the concentrations of THC and CBD.

 

2. Do you have any links to studies looking at the effect legalization has had in use levels, etc. in Washington, Colorado, and other medical marijuana states?
It is always important to be clear about the differences between legalized recreational marijuana and medical marijuana. There is little data showing the effects of legalized recreational marijuana on the four states and the District of Columbia that have it. According to the Colorado Department of Public Health and Environment, legalizing recreational marijuana has not led to an increase in marijuana use by teenagers.

Similarly, an important recent study by Deborah Hasin and colleagues from Columbia in Lancet Psychiatry showed that states with medical marijuana laws have not seen an increase in youth marijuana use compared to states without medical marijuana laws.

It is early to draw definitive conclusions on the effects of medical marijuana and legalized recreational marijuana on marijuana use, but the evidence so far suggests that these marijuana policies do not have the impact upon use, especially youth use, that many feared.

 

3. I heard you say that some cannabinoids are used to treat PTSD? What are some valid medicinal and psychiatric effects of cannabinoids?
There is little published evidence supporting the use of marijuana as a treatment for PTSD. One of the counter-intuitive pieces of science for marijuana is that, while it may lower anxiety in the short-term, it increases anxiety overall (one’s baseline level of anxiety increases when not under the influence of marijuana). Thus, I don’t think marijuana itself will prove to be an effective treatment for PTSD. I would be more optimistic that CBD or other cannabinoids might treat PTSD effectively. There are studies ongoing around the country trying to answer these questions.

We discussed some of the effects of THC and CBD above. We must always keep in mind that these are just 2 of many, many cannabinoids. We are learning more about all cannabinoids each day and science is moving forward. In a few years, it is likely that additional evidence will be uncovered supporting the use of marijuana or cannabinoids for additional medical indications.

 

4. Is it not true, then, that there are beneficial effects of cannabinoids such as an anti-nausea property and others?
Absolutely. There are two cannabinoids available in the United States now—dronabinol and nabilone. They are FDA-approved for two medical indications: 1) nausea and vomiting associated with cancer chemotherapy and 2) appetite stimulation in certain wasting illnesses like HIV. As I wrote in my recent paper in the Journal of the American Medical Association (JAMA) and in my book, Marijuana: The Unbiased Truth About the World’s Most Popular Weed, there is strong scientific evidence to support the use of marijuana and cannabinoids for three other medical indications: 1) chronic pain, 2) neuropathic pain, a type of burning pain some people get in their nerves, and 3) muscle spasticity associated with multiple sclerosis.

 

5. Is it not true, then, that there are beneficial effects of cannabinoids such as an anti-nausea property and others?
Absolutely. There are two cannabinoids available in the United States now—dronabinol and nabilone. They are FDA-approved for two medical indications: 1) nausea and vomiting associated with cancer chemotherapy and 2) appetite stimulation in certain wasting illnesses like HIV. As I wrote in my recent paper in the Journal of the American Medical Association (JAMA) and in my book, Marijuana: The Unbiased Truth About the World’s Most Popular Weed, there is strong scientific evidence to support the use of marijuana and cannabinoids for three other medical indications: 1) chronic pain, 2) neuropathic pain, a type of burning pain some people get in their nerves, and 3) muscle spasticity associated with multiple sclerosis.

 

6. Can high THC level marijuana ever be considered medical marijuana, or just low THC/high CBD strains?
Yes, many times. In fact, insomnia is one of the top three reasons that people tell me that they use marijuana. So many people find it helpful for sleep and many would rather use marijuana than other medications. However, if someone tells me that they are using marijuana to treat insomnia, then we need to carefully evaluate the problem, because they may be less risky ways to treat the problem. As helpful as marijuana can be, it has significant potential side effects.

 

7. Have you heard of individuals using marijuana for insomnia disorder? Have you known for it to be helpful besides using medical medications for sleep disorder?
Yes, many times. In fact, insomnia is one of the top three reasons that people tell me that they use marijuana. So many people find it helpful for sleep and many would rather use marijuana than other medications. However, if someone tells me that they are using marijuana to treat insomnia, then we need to carefully evaluate the problem, because they may be less risky ways to treat the problem. As helpful as marijuana can be, it has significant potential side effects.

 

8. Is there any existing substantial evidence that marijuana is effective for medical needs?
Yes, see my answer to #4 above. Unfortunately, laws in many states recommend the use of medical marijuana for medical conditions for which there is little or no scientific evidence. In such instances, the policy is ahead of the science.

 

9. Could you speak to using marijuana for the treatment of glaucoma?
Although I am not an eye doctor, I get asked this question often, so I have spoken with eye doctors and read on the topic. Treatments for glaucoma aim to lower the intraocular pressure, or pressure within the eye. Marijuana can do this, but it can only do this for 3-4 hours at a time. Thus, to treat glaucoma, one would have to use marijuana 6-8 times per day. In addition, marijuana has other significant potential side effects. These factors, coupled with the fact that there are many safe, effective ways to treat glaucoma, mean that marijuana is not recommended as a treatment for glaucoma by such organizations such as the Glaucoma Research Foundation.

 

Potency

1. Does this dependence statistic (cited in your June 15 webinar) still hold true with the more potent strains readily available?
Great question. It will be important to determine what the impact of stronger marijuana will be. The percentage of adult users who become addicted—9%-- has been corroborated as recently as 2011 in a paper from Dr. Lopez-Quintero and colleagues. Unless there is a major difference due to potency, it doesn’t change the fact that there are millions of Americans who are addicted to marijuana. On the flip side, of course, most people that use marijuana don’t develop addiction, just as most people that drink alcohol don’t develop addiction.

 

2. Will the number of persons addicted to marijuana increase as the %THC increases?
The number of people addicted to marijuana appears to be on the rise. That is likely due in part to the increased potency of marijuana. There are probably other factors as well, though. Will the rate of increase correlate directly with the increase in potency? That is yet another question to be answered.

 

3. Can you speak about the differences between the CBD and THC components of cannabis and also between different strains such as indica and sativa?
The marijuana plant is made up of at least 60 cannabinoids, or components. Unfortunately, we only hear about 2 of these cannabinoids in the mainstream media, THC and CBD. THC is the active ingredient in marijuana that is primarily known for the feeling of euphoria or “high” that many people seek. It has other properties as well—it can reduce inflammation, it can also cause some people to experience psychotic symptoms like hallucinations. CBD is not psychoactive—it won’t make you high. It appears to have anti-anxiety and even anti-psychotic properties. We have heard a lot about CBD lately for these reasons as well as its potential to treat other medical problems. Forms of CBD have produced promising initial results in clinical trials as treatments for certain forms of seizure disorders in children.

Research is lacking on the clinical differences between strains. Cannabis sativa is generally thought to be more activating than cannabis indica, which is widely believed produce a relaxing, calming, or even sedating effect. The ratio of THC to CBD ultimately plays the largest role in the effects produced per dose.

 

Withdrawal

1. DSM V lists decreased appetite as withdrawal symptom, not increased appetite. Can you explain?
Marijuana increases appetite; this is why people associate using marijuana with “getting the munchies.” When you stop using marijuana, the opposite effect can occur, leading to a decrease in appetite.

 

2. When you were speaking about withdrawal, there is actually a syndrome called Cannabinoid Hyperemesis. Have you heard of this and, if so, what are ways that the word can get out to make people aware of this danger?
Yes, I have heard of cannabis hyperemesis syndrome; I receive a couple of calls a month (at least) from patients or doctors describing it. Nausea, vomiting, and possibly dehydration are key symptoms as you noted in the question. Fortunately, stopping use of marijuana usually halts the problems with vomiting. I agree that we need to do a better job educating people about this problem. We can start by mentioning it in forums like this, so thank you for bringing it up.

 

3. Is it common some people have no withdrawals from marijuana use?
Not in my experience, although it is possible. Sometimes people may not attribute some minor withdrawal symptoms like anxiety or irritability to marijuana withdrawal. If people are looking for these symptoms, they are more likely to identify them. More importantly, if they expect these withdrawal symptoms, they are more likely to manage them and avoid relapse back into marijuana use.