Summary: New research from Washington State University found that rats with naturally higher baseline stress hormones are far more likely to self-administer cannabis vapor. Over several weeks, animals were given the opportunity to nose-poke to release brief bursts of cannabis vapor, and those with elevated corticosterone levels displayed the strongest and most persistent drug-seeking behavior.
The study also linked cannabis use to lower endocannabinoid signaling and reduced cognitive flexibility, indicating multiple interacting biological and behavioral predictors of cannabis-seeking. These results point to potential early markers of vulnerability to problematic cannabis use and help explain why chronic stress is often central to habitual consumption.
Key Facts
- Stress predicts use: Rats with higher baseline stress hormones self-administered substantially more cannabis vapor.
- Cognitive flexibility matters: Animals that struggled to adapt to changing rules showed stronger motivation to seek cannabis.
- Endocannabinoid link: Lower endogenous endocannabinoid levels combined with higher morning corticosterone also correlated with increased drug use.
Source: Washington State University
Rats show stress-driven cannabis-seeking, mirroring human patterns
Researchers at Washington State University report that when rats have the chance, they may use cannabis in ways that reflect stress-coping behavior seen in humans. Published in Neuropsychopharmacology, the study measured a wide range of behavioral and biological traits before allowing animals to self-administer cannabis vapor, and then examined which traits predicted stronger drug-seeking.
“Across many behavioral and biological measures, baseline stress hormones stood out as the strongest predictor of cannabis self-administration,” said Ryan McLaughlin, associate professor in WSU’s College of Veterinary Medicine. The team profiled each rat across domains including social behavior, cognition, arousal, and reward processing.
In the self-administration phase, rats had one-hour daily sessions for several weeks. Each time an animal nose-poked a vapor port it triggered a three-second release of cannabis vapor into an airtight chamber. Student researchers tracked nose-poke counts and compared them to pre-existing behavioral profiles and hormonal measures.
By measuring corticosterone—the primary stress hormone in rodents and the analogue of human cortisol—the researchers found a clear association: rats with higher resting corticosterone levels made many more nose-pokes and earned more cannabis deliveries. Importantly, it was the animals’ baseline, resting stress hormone levels that predicted use, not short-term stress responses triggered by acute challenges such as exercise or cognitive challenges.
“The most common reason people report habitual cannabis use is to manage stress, so it makes sense that chronic, underlying stress regulation would predict drug-seeking in this model,” McLaughlin said. Corticosterone measured after exposure to a stressor did not show a significant relationship with cannabis-seeking, reinforcing that trait-like, basal stress physiology was the critical factor.
Cognitive traits also played a role. The researchers tested cognitive flexibility—the ability to shift strategies when rules change—and visual cue reliance. Rats that performed poorly on set-shifting tasks and relied heavily on stable visual cues were more motivated to self-administer cannabis vapor. This pattern suggests that difficulty adapting to changing contingencies may increase vulnerability to repeated drug-seeking.
A biological interaction emerged as well: animals with higher morning corticosterone combined with lower levels of the endocannabinoid anandamide were more likely to use cannabis, though this association was weaker than the link with baseline stress alone. Endocannabinoids are naturally produced signaling molecules that help maintain physiological balance; lower endogenous signaling might make external cannabinoids like THC more attractive as a form of compensation.
“If someone has low endocannabinoid signaling, THC might act as a substitute for those missing signals, increasing motivation to use cannabis,” McLaughlin explained. Understanding these interactions could point toward biomarkers for risk and inform prevention strategies.
As recreational cannabis becomes more accessible, McLaughlin emphasized the importance of identifying individual risk factors that predict problematic use. “These findings highlight potential pre-use markers that could one day support screening and prevention,” he said. Baseline cortisol assessments, for instance, might one day offer insight into who is at greater risk of developing problematic patterns of use.
Key Questions Answered:
A: Rats with naturally higher baseline stress hormone levels were far more likely to self-administer cannabis vapor. This suggests that chronic, underlying stress—not transient, moment-to-moment stress—may be a major driver of cannabis-seeking behavior.
A: Rats with lower cognitive flexibility and a stronger reliance on visual cues showed higher rates of cannabis self-administration. Difficulty adapting to changing rules predicted increased drug-seeking motivation.
A: Rats with high morning stress hormones and lower endocannabinoid levels also showed greater cannabis use. This supports the hypothesis that some individuals may turn to cannabis to compensate for reduced endogenous endocannabinoid signaling, particularly when chronic stress is present.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this stress and cannabis use disorder research news
Author: Josh Babcock
Source: Washington State University
Contact: Josh Babcock – Washington State University
Image: The image is credited to Neuroscience News
Original Research: Closed access.
“Identifying behavioral and biological predictors of cannabis vapor self-administration in rats” by Ryan McLaughlin et al. Neuropsychopharmacology
Abstract
Identifying behavioral and biological predictors of cannabis vapor self-administration in rats
The recent wave of recreational cannabis legalization in the United States highlights the need to identify predictors of individual variability in cannabis use. A subset of recreational users will develop cannabis use disorder, while many others will not, so characterizing traits that confer vulnerability or resilience is essential.
Progress has been limited by a lack of mechanistic insight and few animal models that capture the human route of intake. To address this gap, the researchers used a rat model of cannabis vapor self-administration that employs whole-plant cannabis extract and mimics inhalation, the most common route of human consumption.
Male and female Long-Evans rats (N = 48) completed a battery of behavioral assays aligned with the NIMH Research Domain Criteria (RDoC) framework before beginning self-administration training. After four weeks of daily one-hour cannabis vapor sessions, motivation was tested using a three-hour fixed ratio escalation (FRE) procedure.
Linear regressions showed that domains related to Social Processes, Arousal/Regulatory Systems, Cognition, and Positive Valence significantly predicted the number of cannabis vapor deliveries earned during the FRE test. Specifically, higher basal corticosterone, lower morning anandamide, poorer set-shifting performance, stronger visual cue discrimination, and increased adolescent social grooming each predicted greater responding for cannabis.
The Negative Valence domain did not significantly predict responding. A multivariate machine learning approach combining principal component analysis and permutation importance identified basal corticosterone and set-shifting performance as the strongest predictors of cannabis self-administration. These results underscore the roles of stress regulation and cognitive flexibility as potential risk factors and demonstrate the value of applying the RDoC framework to rodent models with translational relevance.