It appears that rats will often indulge in a bit of cannabis if given the chance, according to new research. But just like many humans, some rodents are more prone to the recreational drug than others. As neuroscientists explain in a study recently published in the journal Neuropsychopharmacology, stressed rats are far more likely to take a hit than their calmer relatives.Â
“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,” Ryan McLaughlin, a study co-author and neuroscientist at Washington State University, said in a statement.
After examining both social behavior and genetic traits including sex, arousal, cognition, and reward, McLaughlin’s team generated a behavioral profile for 48 male and female rats. They then presented the rats with cannabis for one hour a day over three weeks. To access the plant, each rodent would poke their nose into a small port that released a three-second burst of cannabis vapor inside an air-tight chamber. The team tallied the number of “nose-pokes” for each rat, then compared those against their behavioral profiles.
While human stress is largely influenced by the hormone cortisol, the equivalent in rats is called corticosterone. McLaughlin and colleagues compared the rat corticosterone to cannabis use, and saw a clear uptick in nose-pokes for the animals with higher levels of the hormone. Importantly, the cannabis preferences related to resting baseline stress, not situationally induced anxiety from tasks like exercise or puzzles. The team saw another correlation between self-administered cannabis and cognitive flexibility—the ways in which someone adapts to changing rules.
“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,” said McLaughlin. “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.”
Aside from understanding the neuroscience behind cannabis habits, a fuller picture may help inform responsible drug usage, as well as prevention and treatment strategies. For example, someone with a higher baseline cortisol level may become more cautious with their cannabis use, knowing the chances of overreliance on the substance.
“If you want to really boil it down, there are baseline levels of stress hormones that can predict rates of cannabis self-administration,” said McLaughlin. “I think that only makes sense given that the most common reason that people habitually use cannabis is to cope with stress.”
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