A systematic review published in the journal Psychopharmacology Brain reactivity to cannabis cues has been observed in specific brain regions among regular cannabis users. The study also found preliminary evidence that increased brain activity may trigger cravings for cannabis.
Cannabis is one of the most consumed drugs worldwide. Cannabis is becoming more and more legalized, and the substance is becoming more widely available and sold. This may be troubling given the evidence that regular use of cannabis can lead to cannabis use disorders and other psychosocial outcomes.
There is interest in developing intervention strategies to mitigate these negative effects, but the neural processes involved in cannabis use are not well understood. One consistent finding is that regular cannabis users increase their responsiveness to cannabis-related cues, such as odors or attributes. Drug reactivity studies for other substances suggest that this increased reactivity is due to sensitization of reward pathways in the brain. If these reward pathways are activated when exposed to cannabis cues, it may cause cravings or relapse in users hoping to quit.
“I lead the Addiction Neuroscience and Mental Health Program at the Healthy Brain and Mind Research Center at the Australian Catholic University,” said study author Valentina Lorenzetti. “One of our goals is to understand the neurobiological mechanisms of substance use and related disorders, using in vivo and high-resolution neuroimaging tools to image the brain.”
“How the brain processes responses to cannabis cues is important and relevant to our agenda so we can better understand the neural mechanisms that drive cannabis-related cravings in humans. This topic was the focus of our doctoral student Hannah Sell, who has a master’s degree in clinical psychology and is equipped to approach the topic from both a scientific and clinical perspective.
“Given the global trends in the criminalization of medicinal and non-medicinal cannabis, this topic is very relevant, people are exposed to advertisements for cannabis products, stores with cannabis products,” Lorenzetti said. “On the other hand, we know that environmental cannabis cues—such as images of cannabis, a cannabis store, a person using cannabis—can make people want to use cannabis either on impulse or out of habit. In vulnerable individuals, these urges can make it difficult to cut back or stop using them. “When you’re not hungry and you see an ad for pizza and fries, you crave them, and before you know it, you’re buying them at the store.”
Lorenzetti and colleagues conducted a systematic review of the relevant literature. Specifically, they analyzed 18 studies that used functional magnetic resonance imaging (fMRI) to examine brain activity in cannabis users (versus neutral stimuli). Twelve studies were conducted among cannabis users only, while 8 studies were conducted with both cannabis users and controls. The study included a total of 918 participants—603 cannabis users and 315 control subjects.
In a summary of the data, the researchers reported that in 11 of 12 studies conducted exclusively on cannabis users, brain reactivity to cannabis cues was increased compared to neutral stimuli. This increased reactivity was most consistently found in the hippocampus/parahippocampus and amygdala. Seven of the 8 studies that included a control group found that cannabis users responded more to cannabis cues than to neutral cues compared to non-cannabis users. This increased activity occurred in the striatum, prefrontal cortex, and parietal cortex—pathways relevant to addiction. Notably, these brain regions overlap with regions found to be involved in reward processing among cannabis users.
“Findings in the scientific literature suggest that when cannabis users see cannabis-related cues (eg, images, attributes, smells), they may be more likely to crave cannabis,” Lorenzetti told PsyPost. “If you know you are reacting to triggers, seek professional help! There are many empowering and effective strategies to help you successfully manage your cravings for cannabis, how to deal with being surrounded by cannabis ads and stores, and how to stay tolerant of discomfort and cravings. “
Interestingly, 13 of the studies reported associations between brain activity and craving for cannabis. Although these findings were somewhat mixed, some brain regions were more consistently linked to craving—the dorsal striatum, orbitofrontal cortex, amygdala, and insula. The authors of the study noted that these regions of the brain partially corresponded to regions that were differentially activated during exposure to cannabis cues among cannabis users (compared to non-users). This suggests that changes in brain reactivity are responsible for the higher subjective cravings induced by cannabis exposure.
“The findings confirm that there are objective differences in how the brain processes cannabis-related signals, and that in some people this may drive how much they crave,” Lorenzetti explained.
The study authors stated that their review was based on cross-sectional data and that future longitudinal studies are needed. This allows researchers to study how brain activation during cannabis exposure may change as a person increases or decreases cannabis use.
“Now that we’ve established that cannabis use can cause brain changes and cravings in people who use cannabis, we’re trying to figure out how to reduce or eliminate brain reactivity in people who want treatment and are relapsed. to have more control over their use,” said Lorenzetti.
“More research is needed to understand how people respond to cannabis cues, whether they experience problems with cannabis use, and whether this changes after they quit using cannabis permanently. We do not know whether those who use cannabis for medical purposes report such incidents.”
“More scientific evidence is needed to compare how people react to cannabis and other potentially beneficial stimuli, such as high-calorie foods or shopping websites,” Lorenzetti continued. “Is the literature showing these brain changes compelling enough because the studies did not use the comparison stimuli used?”
Although more research is needed, the new findings have some practical implications.
“If you’re a medical professional, seeing signs of cannabis in your treatment plan can increase cravings,” Lorenzetti said. “Also, policymakers who regulate how cannabis products are advertised may cause people to react with passion to images of cannabis, and vulnerable people may relapse.”
“Patterns of Brain Activity Associated with Cannabis Reactivity in Regular Cannabis Users: A Systematic Review of fMRI Studies” by Hannah Sell, Gill Terrett, Lisa-Marie Greenwood, Magdalena Kowalczyk, Hannah Thomson, Govinda Pudel. Victoria Manning and Valentina Lorenzetti.