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New research from Washington State University suggests that stress influences cannabis use not only in people but in rats as well.
Stress-driven cannabis use may not be limited to humans. New research from Washington State University suggests that rats also turn to cannabis when they experience higher levels of ongoing stress.
Study explores why rats seek cannabis
The research, published in the journal Neuropsychopharmacology, focused on understanding what drives cannabis-seeking behavior. The findings showed that rats with naturally elevated stress levels were much more likely to repeatedly self-administer cannabis compared with less stressed animals.
“We ran rats through this extensive battery of behavioral and biological tests, and what we found was that when we look at all of these different factors and all the variables that we measured, stress levels seem to matter the most when it comes to cannabis use,” said Ryan McLaughlin, associate professor in WSU’s College of Veterinary Medicine.
Building behavioral profiles of stressed rats
McLaughlin and his team of undergraduate and graduate student researchers evaluated a wide range of traits, including social behavior, sex differences, cognition, reward sensitivity, and arousal. Using these measures, they created detailed behavioral profiles for each rat. Over a three-week period, the animals were observed for one hour each day while given the opportunity to self-administer cannabis. The rats could trigger a three-second release of cannabis vapor by poking their nose into a vapor port inside an air-tight chamber.
Throughout each session, the student researchers recorded how often each rat performed these “nose-pokes.” When the data were analyzed, the researchers found a clear connection between higher nose-poke counts and elevated baseline stress hormone levels.
Stress hormones strongly predict cannabis seeking
To assess stress, the researchers measured corticosterone in the rats, which is (the equivalent to the stress hormone cortisol in humans). Rats with higher natural levels of this hormone were significantly more likely to self-administer cannabis.
“If you want to really boil it down, there are baseline levels of stress hormones that can predict rates of cannabis self-administration, and I think that only makes sense given that the most common reason that people habitually use cannabis is to cope with stress,” McLaughlin said.
Importantly, the researchers found that long-term, resting stress levels were the key factor. Temporary stress changes caused by exercise or mentally demanding tasks were not linked to cannabis use. Measurements taken after exposure to a stressor also showed no meaningful relationship with cannabis-seeking behavior.
Cognitive flexibility linked to cannabis motivation
The study also revealed meaningful links between cannabis self-administration and “cognitive flexibility,” which refers to the ability to adjust behavior when rules change.
“Animals that were less flexible in shifting between rules, when we tested them in a cognitive task, tended to show stronger rates of cannabis-seeking behavior,” he said. “So, animals that rely more heavily on visual cues to guide their decision making, those rats, when we tested their motivation to self-administer cannabis vapor, were also very highly motivated rats.”
Endocannabinoids and biological vulnerability
Beyond stress hormones, the researchers observed another pattern. Rats with high morning corticosterone levels combined with low endocannabinoid levels were more likely to self-administer cannabis, although this relationship was weaker than the link to baseline stress.
Endocannabinoids are substances produced by the body as needed to help maintain internal balance, a process known as homeostasis.
“There’s some thought behind why people might be more prone to use cannabis, and that maybe THC serves as a reasonable substitute for endocannabinoids in individuals that have lower endocannabinoid levels,” McLaughlin said. “So, perhaps there’s more of a drive to supplement that with cannabis.”
Implications as cannabis access expands
As more states move toward decriminalizing cannabis and allowing recreational use, McLaughlin emphasized the importance of understanding how cannabis affects behavior and how patterns of misuse can develop.
“Our findings highlight potential early or pre-use markers that could one day support screening and prevention strategies,” McLaughlin said. “I could certainly envision a scenario where having an assessment of baseline cortisol might provide some level of insight into whether there’s an increased propensity for you to develop problematic drug use patterns later in life.”
Reference: “Identifying behavioral and biological predictors of cannabis vapor self-administration in rats” by Ginny I. Park, Alexandra N. Malena, Nicholas C. Glodosky, Zachary D. G. Fisher, Carrie Cuttler, Savannah H. M. Lightfoot, Samantha L. Baglot, Cayden Murray, Matthew N. Hill and Ryan J. McLaughlin, 14 November 2025, Neuropsychopharmacology.
DOI: 10.1038/s41386-025-02286-x
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