Cannabis 101: A Q&A with UC San Diego Health’s cannabis experts
It seems like everywhere you turn cannabis or cannabis derivatives can be found. From ingredients in coffee and smoothies to being marketed as medicine, a cannabis craze seems to be sweeping the country. Since 2000, UC San Diego School of Medicine’s Center for Medicinal Cannabis Research and its affiliated researchers have been studying marijuana and its derivatives, their effects on mind and body and their therapeutic potential.
We asked experts to cut through the hyperbole and haze to answer some burning questions.
Answered by Igor Grant, MD, chair of the Department of Psychiatry at UC San Diego
Cannabis is the botanical name for marijuana and contains many chemical compounds. It is believed by researchers that there are more than one hundred different cannabinoids or chemicals present in cannabis. One of the most important ones is tetrahydrocannabinol, or THC. This is the psychoactive ingredient, meaning it's the ingredient that causes people to feel the euphoria or “high” that is generally associated with cannabis. Cannabidiol, or CBD, is another major chemical compound found in the plant. It does not produce the effects of feeling “high” like THC, but is rather associated with reducing anxiety symptoms and being studied to treat seizure disorders and reducing disordered thinking.
Both THC and CBD interact with the body’s endocannabinoid system, a network of neurotransmitters that regulate diverse physiological and cognitive processes and response to stress.
Richard Clark, MD, emergency physician at UC San Diego Health
Urine can test positive for the carboxy metabolite of THC (the one usually tested for in urine screening) for weeks after the last exposure. The more one smokes, the longer one will test positive in the urine. Blood testing is not usually done in the state of California since the active form of THC that is measured in the blood can either last much longer than the clinical effects in chronic smokers, or leave the bloodstream rapidly in occasional smokers who may still have some neurologic impairment, even with negative blood tests. This is why the state has declined to list a “per se” limit of blood THC for driving, electing to judge cannabis driving impairment at this time only on failing a field sobriety test.
Answered by Clark
Pure CBD oil is not supposed to contain THC, or much THC. However, there may be production process differences that may allow a small amount of THC in some CBD products. If there is enough THC in the product, it may cause urine to test positive. It would depend on the purity of the sample.
Mark Wallace, MD, pain management specialist at UC San Diego Health
Scientifically, the answer is yes, and we have clinical trial evidence that suggest cannabis can help alleviate neuropathic pain — a type of pain that is usually chronic and feels like a shooting or burning sensation in the body. Outside of this evidence, we are also discovering that cannabis can be used in place of or in combination with opioids. This is because cannabis, which interacts with the endocannabinoid system, is very similar to the body’s opioid system. This makes it an effective tool to help patients who would like to lower or completely remove opioids from their pain management regimen.
Answered by Grant
Looking at adults and cannabis, which has traditionally had low levels of THC, it appears that the health effects are fairly minimal. Some other popular questions we are asked include:
- Does smoking cannabis cause lung cancer? The short answer is no, unless cannabis is used in combination with tobacco, and the culprit for cancer would be tobacco.
- Does cannabis cause birth defects? There's no evidence to support this in humans.
- Does cannabis cause your immune system to somehow malfunction? Again, there is no data to support this.
- Does cannabis cause brain damage? The answer to this is very unlikely.
Q&A: Cannabis and driving study
Interview with Igor Grant, MD, Distinguished Professor and Chair of the Department of Psychiatry and director of the Center for Medicinal Cannabis Research and Thomas Marcotte, PhD, professor of psychiatry.
Marcotte: Unlike alcohol, which has a generally linear relationship between the amount consumed and being impaired, cannabis has very different pharmacodynamics. One person could smoke a joint and in the first 10 minutes will have very high levels of THC (Tetrahydrocannabinol, the principal psychoactive ingredient), become cognitively impaired during those 10 minutes and then have THC levels that drop rapidly, but remain present over the next hour. This is most common in medical marijuana or habitual smokers. However, another person could smoke the same joint, become cognitively impaired during the first 10 minutes, but then remain impaired for hours. So, when you test blood for THC, you may be able to find someone who has a very high level of THC and is not impaired. On the other hand, you can easily find people who have low levels of THC, but who are impaired.
Marcotte: The cannabis we're using is grown by the National Institute of Drug Abuse (NIDA) on a farm in Mississippi. NIDA is currently the only legal source in the United States for obtaining marijuana to use in clinical trials, and they grow a variety of different strains, contents, THC levels with 13.4 percent being the highest available at this time. Participants in our study smoke cannabis in joint form with a THC content of 0 percent (placebo), 5.9 percent and 13.4 percent. The last percentage is roughly representative of the levels of THC found in confiscated marijuana over the past year or two, but as more sophisticated manufacturing and growing methods are discovered, THC levels are increasing in marijuana.
Grant: The California legislature specifically asked UC San Diego Health to undertake this work because we are the only center in the state to study medicinal cannabis. Since 2000, we have had this mandate, and CMCR has had the experts and facilities to conduct this kind of work.
One of the motivating factors behind the legislature funding our study was the possibility of increasing rates of traffic accidents with pending legalization and more medicinal use. There are some misconceptions around this which are important to note. For example, you'll read that there has been a multiple-fold increase in the number of people involved in accidents who tested positive for cannabis. This statistic may be true, but this doesn't mean cannabis caused or was related to the accident. What is most likely occurring is more testing for cannabis as well as an uptick in cannabis use due to increased legalization and medicinal use. What we know for sure, statistically, is that states that have legalized cannabis have not seen a major increase in traffic accidents overall.
Safe driving is a public health concern for everyone on the roads, and there has been little research done on the effects of cannabis at different doses are on driving. With now both medicinal and recreational cannabis users hitting the roads this has become even more important. California has been pioneer in both the legalization of medicinal and recreational cannabis use, so it’s natural that we are leading the way on this important research.
Grant: The purpose of the study is to take a very detailed look at several aspects of cannabis’ effects on driving. First, we are trying to figure out what is the effect of a dose of cannabis regarding the strength and THC content. Because cannabis has a very complicated pharmacology, it's not so easy to assess the strength and its effects. More information is needed to understand the benefits of testing the blood for THC, and how other possible tests like breath and saliva may be more practical at a roadside check than drawing blood. Second, we want to know how long do any effects last, and how many hours before a person is free from those effects. This is particularly important in terms of medicinal cannabis so physicians can tell patients how long they should not drive after cannabis use. Third, we would like to develop better methods to measure cannabis-related impairments. More specifically, roadside testing, potentially using an iPad or iPhone that could allow law enforcement to instantly assess impairment.
Marcotte: The study is designed in two parts: an initial training day and a test day. The initial training day is to ensure the simulator feels natural to the participant, like an everyday driving experience. Participants will have about an hour of simulation time, including learning specific components of the simulation and going through practice drives. Once comfortable, we'll call them back for the testing day at a later date.
On testing day, participants arrive in the morning and smoke either placebo or active cigarette in a negative pressure room that clears out the smoke. After smoking, participants return to the driving simulator where five simulations will occur over the course of the day. Blood, breath and saliva are collected to test for THC at various steps in the process so we can look at different fluids and their relationship related to driving performance. The aim of these tests is to observe at what time increments (if any) are participants impaired and how long this effect lasts. Additionally, participants complete tests on an iPad that helps measure the cognitive components that might be affected by cannabis.
There are novel challenges to this study. One is that we are doing repeated driving simulator administrations over the course of an entire day. This requires experimenters to coordinate many activities, as well as designing simulations that can be repeated multiple times. For example, some common scenarios we are testing and re-testing include things like determining when it's safe to make a left turn across oncoming traffic; a yellow light dilemma where it's not clear whether a person should accelerate through a yellow light or stop; and a divided attention task like a phone ringing when participants are driving and may take their eyes off the road.
Finally, and unique to this study, participants complete a field sobriety test from trained drug recognition experts.
Grant: Ideal participants for this study are healthy, young adults who have moderate cannabis experience.
Marcotte: We have had great success in getting participants who want to be a part of a novel, important study without having to advertise much outside of Clinicaltrials.gov. Participants are compensated, but do not receive direct feedback on their scores for both the driving simulation and other tasks. However, throughout the course of the day we ask them to estimate whether or not they were impaired and whether or not they suspect receiving active cannabis or a placebo.
Marcotte: A novel component is the attempt to develop cognitive measures that may help law enforcement identify individuals who are impaired due to cannabis. The current field sobriety test was designed to detect alcohol-related impairment through physiological signs, such as staggering or eye movement. This is not the case with cannabis since it typically affects things like time and distance perception. For these reasons, we've created some iPad-based measures for this study that target time estimation, lane tracking and tracking objects over time. We believe these could be better assessments than physiological indicators to see whether or not someone is impaired due to cannabis. It is our hope that through this research, we can enhance or improve the ability of law enforcement to identify impaired drivers.
Grant: Our overall goal is to more clearly understand the time course of cannabis and how that relates to driving safety. We are also trying to understand the relationship between the dosage of THC in a particular product and how that relates to impairment. The practical output of this study is the potential development of a non-blood biological test that a law enforcement officer would be able to use at the roadside, such as a saliva or breath test. Currently, there are some tests available for roadside cannabis impairment testing, but they have not been validated very well. Improved validation is essential, as well as equipping officers with better approaches to testing, such as a tablet-enabled test or adding other kinds of neurological measures that can be done at the roadside specific to cannabis intoxication.
Marcotte: One of the many unique aspects of this study is our collaboration with law enforcement. We are fortunate to partner with California Highway Patrol and local law enforcement officers who have special training in detecting impairment due to various substances. In this study, we're using instructors who have the highest level training and the most experience. When a participant smokes the joint, aside from the driving simulation, they evaluated throughout the course of the day by law enforcement officers who perform different components of the drug recognition evaluation. With this partnership, our goal is to jointly identify which, if any, of the components of their evaluation strongly correlate with participants being impaired.
Grant: This study is focused on smoked or inhaled cannabis, but hopefully future research will look at other topics, such as such as ingested cannabis or absorbed cannabis through a patch or cream. We really don't know how well THC or other cannabinoids are absorbed through these routes and what, if any, is the time course of effect. Hopefully we will conduct another study looking at these other cannabis absorption routes.
Another important area to explore further is how cannabis interacts with other drugs. As of right now, cannabis by itself has only a slight impact on driving when it is the only drug used. However, when combined with other drugs, there is emerging information that suggests cannabis can be a particularly bad combination when a modest amount is mixed simultaneously with alcohol.