NIDA director discusses cannabis, addiction vaccines, and gambling.
Recently, Addiction Inbox was offered the opportunity to submit questions to Nora Volkow, the director of the National Institute on Drug Abuse (NIDA). Dr. Volkow was kind enough to provide detailed answers by email. In her responses, she reveals a broad clinical understanding of addiction, and speculates on what this brain disorder might mean for “other diseases of addiction” like gambling.
Q: Clinical studies, like those by Barbara Mason at Scripps Institute, have documented a marijuana withdrawal syndrome among a minority of users. Are we prepared to say that marijuana is addictive? Why didn't we identify this syndrome years ago?
Nora Volkow: Absolutely, there is no doubt that some users can become addicted to marijuana. In fact, well over half of the close to 7 million Americans classified with dependence or abuse of an illicit drug are dependent on or abuse marijuana. It is important to clarify that while withdrawal is one of the criteria used to diagnose an addiction (which also includes compulsive use in spite of known adverse consequences), it is possible for an individual to suffer withdrawal symptoms without he or she being addicted to an abused substance.
Now, to answer your specific question, the reason for the relatively late realization that people who abuse marijuana can develop a cannabis withdrawal syndrome (CWS) if they try to quit is probably the result of at least two factors. First is the fact (which you hint at already) that a clinically relevant cannabis withdrawal syndrome may only be expected in a subgroup of cannabis-dependent patients. This may be partially explained by marijuana’s uptake into and slow release from fat cells, which can occur over days or weeks after last use. Thus, cessation of marijuana use may not be so abrupt, and could thereby diminish signs of withdrawal. The second factor relates to the small to negligible associations between recalled and prospectively assessed withdrawal symptoms, which may have precluded many previous, recall-based studies from detecting or properly characterizing CWS. It is also worth pointing out that other addictions (e.g., cocaine) were also not initially thought of as capable of triggering withdrawal symptoms.”
Q: Are there any anti-craving medications you are particularly excited about at this time?
Volkow: In the context of nicotine addiction, we have a host of nicotine replacement options as well as 2 medications that work through different mechanisms—all of which reduce craving and the risk of relapse during a cessation attempt, particularly when combined with some form of behavioral therapy. However, sustained abstinence from nicotine has been difficult to achieve, even with the current therapeutics that are available. So, at this point, I am very excited about a novel approach to the treatment of addiction—an approach that relies on vaccine development. Currently there are anti-nicotine vaccines in clinical testing, which are designed to capture the nicotine molecules while still in the bloodstream, thus blocking their entry in to the brain and inhibiting their behavioral effects. And while these vaccines were not intended specifically to reduce cravings, they appear to be effective in helping subjects who develop a high antibody response sustain abstinence over long periods of time. Even those people with a less robust antibody response to the vaccine, decreased their tobacco use. So this approach appears very promising.
Similarly, in the context of opiate addiction, we are very excited about the cumulative positive results of the clinical experience so far with buprenorphine, a long-acting partial agonist that acts on the same receptors as heroin and morphine, relieving drug cravings without producing the same intense "high" or dangerous side effects.
Q: You have suggested in the past that certain forms of overeating are addictions. There is good evidence for this. What about non-substance addictions, like gambling?
Volkow: The brain is composed of a finite number of circuits, for, for example, rewarding desirable experiences, remembering and learning about salient features and stimuli in the environment, developing emotional connections to other members of the social group, becoming aware of changes in interoceptive (internal) physiological states, etc. These and a few others are the circuits that the “world” acts upon. So it is almost by necessity that we’ll find significant overlaps in the circuits that mediate various forms of compulsive behaviors. We have yet to work out the details and the all important differences, but it stands to reason that there will be many manifestations of what we can call diseases of addiction. Thus, addiction to sex, gambling, alcohol, illicit drugs, shopping, video games, etc. all result from some degree of dysfunction in the ability of the brain to properly process what is salient, accurately predict and value reward, and inhibit emotional reactivity or deleterious behavior.
Volkow: The brain is composed of a finite number of circuits, for, for example, rewarding desirable experiences, remembering and learning about salient features and stimuli in the environment, developing emotional connections to other members of the social group, becoming aware of changes in interoceptive (internal) physiological states, etc. These and a few others are the circuits that the “world” acts upon. So it is almost by necessity that we’ll find significant overlaps in the circuits that mediate various forms of compulsive behaviors. We have yet to work out the details and the all important differences, but it stands to reason that there will be many manifestations of what we can call diseases of addiction. Thus, addiction to sex, gambling, alcohol, illicit drugs, shopping, video games, etc. all result from some degree of dysfunction in the ability of the brain to properly process what is salient, accurately predict and value reward, and inhibit emotional reactivity or deleterious behavior.
As we learn more about the significant overlaps at the genetic, neural, circuit, and systems levels we may be able to reap the benefits from complementary research into these various chemical and behavioral addictions.
Photo Credit: http://www.thechallenge.org
