Five things we’ve learned about marijuana

University of Washington professor Jason Kilmer has studied the effects of marijuana use on students since the drug became legal in the state in 2012. Photo by Adam Glanzman/Northeastern University

As Massachusetts prepares to open its first recreational marijuana dispensaries on Tuesday, the Office of Prevention and Education at Northeastern is working to ensure that students and staff understand the potential drawbacks of smoking weed.

“If we look nationally, we have seen a pretty significant shift in attitudes,” said Amaura Kemmerer, who directs OPEN, which provides supportive, non-judgemental services to students on the topics of alcohol, drugs, sexual violence, and sexual health. “We’ve seen the perception of risk from using marijuana plummet. That’s been fairly predictive of increasing use.”

While proponents of the drug will argue that marijuana is as safe as alcohol (or safer), research is showing otherwise.

“We can talk to students about less risky drinking, about serving size. We know the exact point at which decision making is impaired with alcohol. We know the exact point at which a blackout is likely to occur,” Kemmerer said. “We don’t know any of this for marijuana.”

Kemmerer recently invited Jason Kilmer, a marijuana expert from the University of Washington, to Northeastern’s Boston campus to discuss marijuana use in college students with faculty and staff.

Here are a few of the takeaways from Kilmer, who has been collecting data on marijuana use in subjects aged 18 to 25 since the first dispensaries opened in Seattle in 2014.

Just because it’s legal in the state doesn’t mean you can use it on campus.

Regardless of state laws, at the federal level cannabis is an illicit drug with no accepted medical use and a high potential for abuse.

As a result, any schools that allow marijuana use could lose their federal funding. One school in Washington has already been cited for failing to comply with federal law, Kilmer said. “We’re waiting for news of what their penalty will be.”

Today’s weed is more potent than anything we’ve studied

Tetrahydrocannabinol, or THC, is the main psychoactive ingredient in marijuana and typically used as a measure of potency. Over the past decade, the quantity of THC in marijuana in the United States has risen steadily, but the change has been more dramatic where there is a legal market.

A study published in 2016 tested over 38,000 samples of marijuana seized by the Drug Enforcement Administration between 1995 and 2014. The average THC content in 1995 was around 4 percent. By 2014, it had risen to 12 percent.

“The average THC content of marijuana for sale in stores in Seattle is 21.62 percent,” Kilmer said. In concentrated oils, it can be over 70 percent.

Over the past decade, the quantity of THC in marijuana in the United States has risen steadily, but the change has been more dramatic where there is a legal market for the drug. Photo by iStock.

It might help you fall asleep, but it won’t help you rest.

Weed is a sedative hypnotic, Kilmer said. It will help you crash out at bedtime, but don’t expect to feel well-rested the next day. Using marijuana interferes with the body’s natural sleep cycle, causing “significant increases in daytime sleepiness, anxiety, irritability, and jumpiness,” Kilmer said.

In a healthy sleep cycle, your body should rotate between deep sleep and Rapid Eye Movement sleep, when most dreams occur, several times through the night, spending less time in deep sleep with each cycle. But a review of sleep-related studies showed that marijuana use increased the amount of time spent in deep sleep and deprives the body of REM sleep.

It messes with your head for longer than you think

THC affects your hippocampus, Kilmer said, the area of the brain associated with thinking and processing information.

“After cannabis use, the neurons in the hippocampus get suppressed,” Kilmer said. “They fire, but they fire at a rate that is lower and slower than they could or should be firing.”

An experiment published in 2001, which paid consistent marijuana users to stop, found that it took four weeks for cognitive impacts to fully fade. A similar study in 2010, focusing specifically on teenage users, showed some effects wore off after two or three weeks, but attention deficits remained for at least three weeks.

“If you have a drink today, I have no proof of that tomorrow,” Kilmer said. “But if you use marijuana today, we can measure the cognitive effects.”

Think you’re good to drive? Think again.

“After stores opened, we saw fatalities with THC double in one year,” Kilmer said. “In the state of Washington, drugged-driving deaths now outnumber drunk-driving deaths.”

Marijuana legislation in Washington State set the legal limit for driving with THC in your bloodstream at five nanograms per milliliter of blood. At that level, people have the same difficulties with reaction time and shifting focus seen at the legal limit for blood-alcohol content.

But how long does it take for THC to leave your system? A study in 2007, when THC content was lower, said it took three hours for men averaging 154 pounds to drop below 5ng/ml, and longer for women or heavier men. Newer studies recommend waiting closer to five or six hours before getting behind the wheel.

“If it’s edibles? Don’t drive that day,” Kilmer said.

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