A systematic review published in the journal Psychopharmacology found increased brain reactivity to cannabis signals in regular cannabis users, in specific brain regions. The study also revealed preliminary evidence that this increased brain function may trigger cannabis cravings.
Cannabis is one of the most widely used drugs in the world. As cannabis becomes more and more legalized, the substance is more heavily marketed and made available. This can be troubling, as there is evidence that regular cannabis use can lead to cannabis use disorders and other psychosocial consequences such as lower IQ and poorer cognitive performance.
There is interest in developing intervention strategies to mitigate these negative effects, but the neural processes associated with cannabis use remain poorly understood. A consistent finding is that regular cannabis users exhibit an increased reactivity to cannabis-related cues, such as scents or paraphernalia. Drug cue reactivity studies for other substances suggest that this increased reactivity is due to the sensitization of reward pathways in the brain. If these reward pathways are activated during exposure to cannabis cues, it could potentially lead to cravings or relapse in users hoping to quit.
“I lead the Neuroscience of Addiction 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 focuses is to understand the neurobiological mechanisms of substance use and related disorders, using neuroimaging tools that create high-resolution, in vivo images of the brain.”
“How the brain processes reactivity to cannabis signals is important and fits our agenda so that we can better understand the neural mechanisms that may trigger people’s cannabis-related cravings. This topic was the focus of our PhD student Hannah Sehl, who has a master’s degree in clinical psychology and is equipped to approach the topic from a scientific and clinical angle.”
“The topic is getting very hot, given the global trends towards decriminalization of medicinal and non-medicinal cannabis, people are exposed to more cannabis product ads, cannabis product shops,” said Lorenzetti. “On the other hand, we know that cannabis cues in the environment – such as images of cannabis, a shop selling cannabis, someone using cannabis – can induce people to want to use cannabis and crave cannabis because of an impulse or habit. In vulnerable people, these cravings can make it difficult to reduce their use or remain abstinent. It’s like you’re not hungry, but then you see an ad for pizza and chips, you end up craving them, and before you know it you end up in a store to buy them and eat them.”
Lorenzetti and her colleagues conducted a systematic review of the related literature. In particular, they analyzed 18 studies that used functional magnetic resonance imaging (fMRI) to examine the brain function of cannabis users during exposure to cannabis cues (versus neutral stimuli). Twelve studies were conducted only among cannabis users and 8 studies among cannabis users and controls. The studies included a total of 918 participants – 603 cannabis users and 315 controls.
In their summary of the data, the researchers report that 11 of 12 studies conducted only in cannabis users found increased brain reactivity to cannabis signals compared to neutral stimuli. This increased reactivity was most consistently found in the hippocampus/parahippocampus and the amygdala. Seven of 8 controlled studies found that cannabis users showed more reactivity to cannabis cues than to neutral cues compared to non-cannabis users. This increased activity mostly occurred in the striatum, prefrontal cortex, and parietal cortex – addiction-relevant pathways. In particular, these areas of the brain overlap with areas that have been found to be involved in reward processing in cannabis users.
“The findings from the scientific literature confirm that when people who use cannabis see cannabis-related cues (such as images, paraphernalia, smells), they can be triggered to crave more cannabis,” Lorenzetti told PsyPost. “If you are aware that you are reacting to triggers, seek professional help! There are many empowering and effective strategies that can help you successfully manage cannabis cravings, deal with the presence of cannabis ads and shops, and become more tolerant of discomfort and cravings. ”
Interestingly, 13 of the studies reported associations between brain activity and subjective cannabis cravings. While these findings were somewhat mixed, certain brain regions were more consistently linked to cravings — the dorsal striatum, orbitofrontal cortex, amygdala and insula. The study authors noted that these brain regions partially overlap with regions found to be differentially activated in cannabis users (vs. non-users) during exposure to cannabis cues. This may indicate that altered brain reactivity is responsible for causing higher subjective cravings when exposed to cannabis cues.
“The findings confirm that there are objective differences in the way the brain processes cannabis-related signals, and in some people this may determine how much they desire,” explains Lorenzetti.
The study authors indicated that their assessment was based on cross-sectional data and that future longitudinal studies are needed. This would allow researchers to explore how brain activation during cannabis exposure may change as a person’s cannabis use increases or decreases.
“Now that we have established that cannabis use can cause cravings and brain changes in people who use cannabis, we are trying to find how such brain reactivity can be reduced or eliminated in people seeking treatment and vulnerable to relapse, or in those who want to be more in control. about using it,” said Lorenzetti.
“More studies are needed to understand how people respond to cannabis cues, changes depending on whether or not they experience problems with their cannabis use, and after they stop using cannabis for good. We also don’t know if people who use cannabis for medical purposes report similar experiences.”
“More scientific evidence is needed to compare how people respond to cannabis and to other stimuli that may also be rewarding – such as high-calorie foods or shopping websites,” Lorenzetti continued. “Is the literature demonstrating these brain changes, because studies didn’t use comparison stimuli that were used, appealing enough?”
Despite the need for more research, the new findings have some practical implications.
“If you’re a health professional, you can factor in the treatment plan that seeing signs of cannabis can increase cravings,” Lorenzetti said. “Also, policymakers who regulate how cannabis products are advertised may be responsible for the fact that people may respond to cannabis images with cravings, and vulnerable people may relapse.”
The study, “Patterns of brain function associated with cannabis cue-reactivity in regular cannabis users: a systematic review of fMRI studies,” is written by Hannah Sehl, Gill Terrett, Lisa-Marie Greenwood, Magdalena Kowalczyk, Hannah Thomson, Govinda Poudel, Victoria Manning and Valentina Lorenzetti.