The Unbiased Truth About the World's Most Popular Weed
By Kevin P. Hill, M.D.
Myth: Marijuana Use Cannot Lead to Addiction
On a handful of occasions each year, I find myself in meetings with doctors from other specialties. At each of these meetings, we begin by going around the room describing, in a few sentences, who we are and what we do. I always mention that I am an addiction psychiatrist who conducts research in hope of finding a medication to treat marijuana addiction. While that introduction does not produce audible gasps, one or more of these doctors will invariably come up to me at a break in the proceedings and say “Marijuana? I thought that wasn’t addictive.”
When I first heard other doctors say that they thought marijuana was not addictive, I was surprised. Over the years, however, I realized that these doctors are simply reflecting a common myth about marijuana: that its use cannot lead to addiction. As we learned earlier, marijuana is potentially addictive—9 percent of adults and 17 percent of adolescents who use in the United States develop addiction, resulting in 2.7 million Americans meeting criteria today for marijuana addiction. Causing addiction usually means causing harm, so understanding
how marijuana use can lead to marijuana addiction in some who use is important because this myth reinforces the first Marijuana Myth that we discussed in Chapter 3: “Marijuana is not harmful.”
Because people usually don’t think of marijuana in the same way that they think of “hard drugs,” they often make the leap to thinking that marijuana is not harmful at all. The science, however, suggests that marijuana—considered a “soft drug” by many—shares much in common with hard drugs known for their addictive qualities. In this chapter I will show how marijuana can be addictive for some people—causing problems in multiple areas of life—and that marijuana addiction is a brain disease that is expressed as a compulsive behavior.
Key Factors in Marijuana Addiction
Historical (genetic), environmental, and physiological factors play a role in whether someone will become addicted to marijuana.
Historical (genetic) factors
Historical factors encompass both family history, including a family history of addiction, as well as previous experiences with drugs and alcohol. Addiction is a chronic medical illness like asthma, diabetes, or high blood pressure. These chronic medical illnesses have a genetic component, which explains why it has been shown many times that if someone in your family struggled with addiction, you are at higher risk for having addiction problems than someone with no family history of addiction. For example, Jason is at higher risk for developing problems with addiction because his father is addicted to alcohol.
Heritability refers to the proportion of the observable trait (addiction in this case) that can be attributed to inherited genetic factors as opposed to environmental factors such as the kind of neighborhood in which you live. The proportion of heritability attributed to genetic factors and environmental factors varies according to different research studies, but, for example, one study conducted in 2007 showed that genetic factors accounted for 35 percent (about one-third) of the heritability of marijuana addiction and environmental factors accounted for 47 percent (about one-half).30 That’s just one study. Looking over a variety of studies, we can say that researchers have agreed that genes play a role in marijuana addiction, but they have not agreed on how large that role is. Your environment (family behaviors, schools, friends, neighborhood, and other “external” factors) also play a role. Jason’s neighborhood, where he felt that it seemed as though “everyone” used marijuana, probably made it more likely that he began using marijuana on a daily basis.
You are not doomed if you have genes for addiction from your family, but if you have a family history of addiction, and therefore genes for addiction, you do need to be more careful about your exposure to alcohol or other drugs. So, for example, working in environments with easy access to drugs or alcohol—such as bars, pharmacies, or hospitals—may not be the healthiest choices if you have a family history of addiction. Similarly, having friends who use mood-altering substances more than most people increases the likelihood that you will “express” your addiction genes and get into trouble.
Environmental factors, such as one’s daily social interactions, play a large role in the development of addiction. Let’s start with some influences that should be obvious to most of us—factors that influence the choices of a person who is already addicted or well on the road to addiction. For example, living in close proximity to family members or friends struggling with addiction makes it more difficult for someone with genetic predisposition to addiction to stay away from drugs. Again, this predicament made things more difficult for Jason in our case study. Similarly, if a person is in recovery—having established a drug-free lifestyle—being around those who are using drugs or alcohol regularly is risky. These situations contain cues, or signals, in the form of behaviors or objects that trigger a craving or desire to
use drugs. Those with a history of addiction have a high level of sensitivity to these signals (called cue reactivity). A person with a history of alcoholism, for example, will react far more strongly to seeing someone drink alcohol than someone without such a history. Due to this high level of cue reactivity and the likelihood that such cues can trigger a relapse, many types of talk therapy treatments for addiction try to modify the addicted person’s response to cues via learning and memory. Patients learn alternative ways to respond to potentially triggering cues and then, when confronted with these cues again, remember that these cues do not necessarily mean that a relapse will occur.
Physiological factors play a large role in addiction. This is not a surprise, given that many people have touted addiction as a “brain disease.” Addiction causes your brain to undergo changes at its most basic levels—within the cells, which are the building blocks of your body’s organs, including the brain. These changes occur immediately (also called acutely) in response to a cue, a stressor, or drug use itself. They also occur after an extended period of use (also called chronically). Here’s how that works.
Drug use leads to the release of brain chemicals called neurotransmitters. One of these chemicals, dopamine, is released in an area of the brain called the nucleus accumbens, or pleasure center. Research shows that dopamine levels in the brain surge after someone engages in a pleasurable activity. Your body associates the activity with the good feelings of a dopamine surge and you want to perform the activity again in order to get that pleasurable sensation again. These surges are seen in response to sex, eating, consumption of alcohol, and the use of other drugs, including marijuana. These surges help to explain why some people smoke marijuana every day, even though it harms other areas of their lives. It is important to point out that marijuana use results in the same type of dopamine release as taking other addictive drugs or engaging in compulsive behaviors like sex, overeating, and gambling. Using drugs like marijuana causes immediate changes to brain cells and some changes that take place chronically, over time. When a person uses drugs, the drugs are taken into the body and then they are broken down into chemicals that bind to receptors. The chemicals are the “keys” plugging into the receptors, which are the “locks.” When people use drugs over and over, this process occurs again and again, and after time, the receptors get worn out and the body cannot produce enough new receptors to replace the worn out ones. The result is what is called down-regulation, the decreased production of the particular receptors associated with the drug being used.
A reduction in the number of receptors is one factor in the development of tolerance. Tolerance means that a substance user must use an increasing amount, or dose, of a drug in order to get the same effects that they got from a lower dose of the drug when they first began to use. When the receptor numbers are reduced, the user tries to compensate by using more drugs. Those with addiction commonly describe this predicament, where they need to use more and more of the drug to get the same effect. Getting more and more of the drug usually leads to an entirely new set of problems, such as how to find and afford the larger amount.
Other medical conditions or psychiatric illnesses can play an important role in the addiction process. Depression is a classic example. People suffering from depression may look to alcohol or other drugs to escape their low mood and other symptoms of depression that bother them. The use of drugs in these cases may only lead to temporary relief from their problems or uncomfortable feelings. Ultimately, use of mood-altering substances often exacerbates feelings of depression, especially when the feelings of being intoxicated subside.
As noted earlier, anxiety is another example that is particularly relevant to marijuana use. Many people who use marijuana say that they use it to treat anxiety. While we explained in Chapter 3 how regular marijuana use actually leads to worsening anxiety over the long term, clearly many people would not use marijuana nearly as frequently if they were not bothered by symptoms of anxiety. This is why, when someone seeks treatment for either anxiety or problems with marijuana use, the clinician needs to ask about the other in the clinical interview. It is important to understand why someone would use marijuana and it is also important to understand what someone’s anxiety may revolve around. When you keep in mind the important relationship between anxiety and marijuana, it is easy to appreciate how the effective treatment of anxiety, either with talk therapy or medications, can play an important role in someone’s marijuana use.
Marijuana, or weed, pot, grass, MJ, Mary Jane, reefer, cannabis, or hemp among dozens of other names, has a long, colorful history dating back more than 2,000 years as the one of the most sought-after, mood-altering substances in the world. Societal opinion about the drug has dramatically swayed over the years, from viewing it as a grave danger to society in the 1930s film Reefer Madness, to a harmless recreational high in the '60s, to an addictive substance and gateway to such “hard” drugs as heroin today. The myths and misinformation about marijuana have only multiplied over the years as the controversy over legalization and medical marijuana grows.
A nationally recognized clinical expert and leading researcher on marijuana, Kevin P. Hill provides a comprehensive guide to understanding the drug in Marijuana: Cutting through the Myths about the World's Most Popular Weed. Through research-based historical, scientific, and medical information, Hill will help you sort through what you hear on the streets and in the media and cut straight to the facts. Whether you're a parent concerned about your child's use, someone with an illness considering medical marijuana as a treatment option, a user who has questions about its effect on your health, or if you're just trying to make up your mind about legalization, this book will give you the most current and unbiased information you need to make informed decisions about marijuana.
Kevin P. Hill, M.D., M.H.S., is an Assistant Professor of Psychiatry at Harvard's McLean Hospital in Belmont, Massachusetts, and an addiction consultant with a number of professional sports organizations. His marijuana research is funded by the NIH, the Brain and Behavior Research Foundation, and the American Lung Association. In 2013 he was awarded the Alfred Pope Award for Best Research Paper by a Young Investigator at McLean Hospital, and he has authored or coauthored articles in more than thirty peer-reviewed scientific publications.