Marijuana Addiction Changes Brain’s Response to Drug Cues
Marijuana has a largely benign reputation in much of the U.S., in part because many people somewhat misguidedly compare the drug’s potential harm to the potential harm associated with excessive alcohol use. Despite this reputation, roughly 9 percent of the total pool of marijuana users will eventually meet the terms used to diagnose cannabis addiction, the National Institute on Drug Abuse reports. Specific groups of users have much higher risks for receiving such a diagnosis. For example, when adults are excluded, the addiction rate rises to approximately 17 percent, whether a teenager initially uses marijuana regularly or only occasionally. When regular or habitual users are considered separately (and regardless of age), the addiction rate spikes to at least 25 percent and may rise twice as high to 50 percent. Habitual users who try to stop smoking marijuana commonly report the presence of withdrawal symptoms that interfere with the success of their quit attempts.
Whenever you perform any action repeatedly over time, you can develop conscious and unconscious expectations about such things as the setting where that action takes place, the people who perform the action with you and the likely outcomes of the action. Every time you enter a situation where you’ve performed the action in the past, your preexisting expectations can increase the likelihood that you will respond in certain ways. For example, if you regularly smoke marijuana (or use any other substance) in certain situations, your expectations can increase your conscious and unconscious desire to use the drug each time you encounter these situations in the future. Researchers and addiction specialists refer to these reinforcers of substance-using behavior as drug cues. In any given circumstance, a drug cue can arise internally from your thoughts and emotional reactions or externally from your local surroundings (including your physical location and the behaviors of the people around you).
Effects of Addiction
In the study published in Drug and Alcohol Dependence, the University of Texas at Dallas researchers used real-time brain scans called fMRI scans to examine the ways in which people addicted to marijuana respond to drug cues. The researchers used the same procedure to compare the responses of marijuana users affected by addiction to the responses of non-addicted marijuana users. The study was undertaken, in part, because of the known role that drug cues can play in making a person in substance recovery susceptible to a loss of abstinence and a relapse back into active substance use. A total of 71 regular marijuana smokers took part in the project. Approximately 50 percent of these participants were addicted to the drug, while the remainder had not developed addiction symptoms. All of the participants in both groups had their brain functions analyzed while holding either a previously used marijuana pipe (the active drug cue) or a pencil of roughly the same size and shape (the placebo or inactive drug cue).
The researchers found that both the addicted and non-addicted users experienced a similar increase in activity in their brains’ pleasure centers while holding the marijuana pipe. However, they also noted that supporting or secondary brain activities were quite different in the two groups. In the non-addicted group, activity increased in the parts of the brain responsible for memory function and maintaining attention. Conversely, in the addicted group, activity increased in parts of the brain responsible for regulating emotional responses.
The study’s authors concluded that the brain activity changes found in the group affected by marijuana addiction largely mirror the changes found in people addicted to cocaine and other substances. They believe that this finding reinforces the very real possibility of getting addicted to the drug. In addition, they believe their overall findings indicate that public health efforts to intervene in problematic marijuana use need to take each individual’s degree of progression toward addiction into account.