Recreational marijuana use is now legal in eight states plus the District of Columbia, giving public health researchers more leeway than ever to investigate some of the foundational underpinnings of cannabis culture: How much weed is in a joint? What happens to your brain when you get high?
You might be surprised to learn that the research to date on this question is mixed. One recent study found that while low doses of THC (the active chemical compound in pot) helped people cope with stressful situations, moderate to higher doses actually made people stress out even more.
But that particular study simply measured the effects of a single dose of THC — what about the effects of repeated heavy cannabis use?
Enter new research from Washington State University, recently published in the journal Psychopharmacology. The study recruited two groups of 40 people: One group had used marijuana nearly every day for at least a year, and the other comprised people who weren't marijuana users.
Half of each group, users and nonusers, was subject to a particularly anxiety-inducing laboratory test commonly used to measure stress responses: They had to dunk their hands in a container of cold water for anywhere from 45 to 90 seconds, and then count backward from 2,043 by 17, getting reprimanded by lab workers whenever they got a number wrong.
As if that weren't bad enough, they were also shown a live video feed of their faces as they attempted to count.
The other half of each group was subject to a non-stressful “control” scenario: Dip a hand in warm water, count from 1 to 25, no reprimands, no video.
The meat of this study comes from comparing the stress responses of the cannabis users and the nonusers. To assess this, the researchers measured the amounts of cortisol, the body's primary stress hormone, in the subjects' saliva immediately after they took the stress tests.
“Despite abstaining from cannabis use on the day of testing,” the researchers found, “cannabis users exhibited no increase in salivary cortisol concentration in response to the stress manipulation compared to non-users” [emphasis added]. For a sanity check, the researchers also had the subjects self-evaluate their perceived levels of stress. Same finding: Nonusers rated themselves as more stressed out than the chronic marijuana users.
The heavy users, in other words, reacted to a stressful situation with equanimity and chill even though they weren't stoned at the time of the test. There's an outside chance that some of this effect could be due to self-selection: Perhaps naturally relaxed people are more inclined to become frequent cannabis users? But the effects were observed in a controlled laboratory experiment, making the causal link much stronger than it would have been if the researchers had just relied on, say, preexisting survey data.
This is somewhat unsurprising: Surveys show that “relaxation” is the No. 1 reason cited by marijuana users for why pot is their drug of choice. This research confirms that they're probably not just deluding themselves and that over the long term, marijuana use does perhaps lead to a somewhat more relaxed outlook on life.
But, as the researchers note, this can be a double-edged sword. Stress is an adaptive response to potentially dangerous or harmful situations. Dampening that response in otherwise healthy individuals may have unintended consequences: Prior research has shown links between unbalanced cortisol levels and PTSD and depression, for instance.
On the other hand, stress and anxiety can be debilitating conditions in and of themselves. For certain individuals, self-medicating with pot may provide an optimal level of stress relief without risk of some of the nastier side effects of prescription medications, for instance.
Stress aside, chronic marijuana use is linked to its own host of potential side effects. Deliberately altering your brain's chemistry — via pot, alcohol, prescription meds or anything else — is a delicate balancing act. The liberalization of marijuana laws in Washington and other places is bringing some of that balance into sharper focus.