Researchers with Washington State University have found cannabis use may diminish a user’s physiological response to stress in a study published recently in the journal Neurobiology of Stress.
In the study, female rats that self-administered daily puffs of cannabis vapor for a month had lower blood levels of a hormone associated with stress when confronted with a stressful situation than they did at the start of the experiment or when compared to a control group.
In previous studies conducted by WSU assistant professor of psychology Carrie Cuttler, another co-author on the paper, cannabis users showed a more muted response to stress conditions when compared with nonusers. She said the purpose of this most recent study was to establish the “direction” of this effect — in other words, does cannabis use diminish a person’s stress response or are people with a blunted stress response more likely to use cannabis?
While they were able to establish a relationship between lower stress and cannabis use, Cuttler said animals that started the experiment with a more muted response to stress did not self-administer more cannabis. While a diminished response to stress may seem desirable to some, Cuttler said it is likely more complicated than simply being less stressed.
“We don’t know if this is a good thing or a bad thing and there’s reason to argue for either of them at this point — a blunted stress response might actually predispose some people to certain mental health conditions is our concern,” she said. “So yeah, it sounds great on the surface that maybe they’re less prone to stress … but the stress response is an important system that exists for a reason — any alterations in that or perturbations in that system may or may not be a good thing.”
For the study, rats were trained to trigger an infrared sensor to activate a machine that would provide a small puff of cannabis vapor any time they felt the urge. Researchers measured the levels of stress hormone in the rats’ blood both before and after the experiment and were also compared to a control group that was given no access to cannabis vapor. Male rats did not experience the same effects, but they also self-administered a lot less of the drug, which may explain the disparity, researchers said.
WSU assistant professor and co-author on the paper Ryan McLaughlin said the ability of the rats to choose when they wanted cannabis, as opposed to injecting the animals with THC or other cannabinoids, was an important feature of the experiment. He said just the nature of being forcefully injected with a drug can fundamentally change which neurobiological systems and circuits are recruited and altered by the drug and may yield different results than when it’s voluntary. He said this model is a much more reliable analogue for human behavior in seeking and using the drug.
“Humans don’t inject cannabis, so injecting cannabis or injecting THC into a rat is problematic,” McLaughlin said. “It’s not just about getting the drug into the system, it’s about what the drug does once it gets in the system — how it gets metabolized, how it gets broken down and how it has its effects biologically.”
McLaughlin said because there are ethical and legal concerns with randomly assigning human subjects to be cannabis users or nonusers, this kind of experimentation is limited to animal models. While there are some hurdles to overcome while studying behavior, he said rat brains are a surprisingly good physiological facsimile for studying human brains. He said this is especially true of “highly conserved” neurological processes like stress.
“The stress response is something that’s conserved all the way down the evolutionary line,” he said. “So the basic machinery and all the parts and pieces that are involved in the stress response, are the exact same rodent as they are in a monkey or a human.”