THC Content in Cannabis Has Surged: Here’s What You Need to Know
BU experts offer advice for how to protect yourself
THC levels in cannabis have quadrupled since the 1990s, raising potential health risks. Photo via iStock/User44916d0b_828
THC Content in Cannabis Has Surged: Here’s What You Need to Know
BU experts offer advice for how to protect yourself
With recreational use of marijuana now legal in 24 states, access to cannabis has soared in recent years. So too has its THC content—to potentially dangerous levels.
Whereas in the 1990s, cannabis averaged less than 4 percent THC—the main psychoactive ingredient of the cannabis plant—that level quadrupled by 2022, according to the National Institute on Drug Abuse. That’s a concern at Boston University’s Student Health Services (SHS).
“The trend toward increasing potency of THC is definitely an issue and is well-documented,” says Matthew Lally, staff psychiatrist in behavioral medicine at SHS. “The efforts to legalize cannabis prioritized a messaging campaign that cannabis was good for health, reduced risk of opioid addiction, etc. These same messages are evident now in commercial advertising.
“The evidence is also clear that in states where cannabis has been legalized, rates of use have gone up, with college age being the highest rate of increase,” he adds. (Massachusetts is one such state, with gross cannabis sales last year at a record $1.6 billion-plus.)
In part, that rise in use may be due to the ease of using electric cartridges and devices to consume cannabis, Lally says: “Students tell me they feel the electric devices are more addicting because they are always right there, so quick and easy to use, and hard to take a break from.”
Cannabis does have medicinal value in some cases, such as decreasing nausea from chemotherapy or reducing elevated eye pressure, he adds, but “the evidence is clear that frequent cannabis use worsens mental health.” (Infrequent use is not a concern, Lally says.)
He and Sarah Voorhees (SPH’13), SHS assistant director of substance use, recovery, and sexual well-being, spoke with BU Today about the symptoms and dangers of excessive THC consumption and their advice for students who are using cannabis.
Q&A
with Matthew Lally and Sarah Voorhees
BU Today: Do we know how many BU students use cannabis?
Voorhees: The 2025 Healthy Minds Study at BU gives a snapshot of students’ cannabis use: 22 percent of respondents said that they have recreationally used cannabis products that contain THC, including smoking, vaping, and edibles, over the past 30 days.
BU Today: What are the symptoms of, and possible dangers from, excessive THC consumption?
Lally: I wrote a presentation that I’ve given to college mental health clinicians across the country because I saw so many college students presenting with mental health concerns—mostly depression, anxiety, and purported ADHD—and using cannabis daily. I did a thorough review of the scientific literature, and it became clear the frequent cannabis use was often the cause—not a consequence—of the depression, anxiety, and inattention problems.
For some students, mental health difficulties existed before frequent cannabis use, but this was pretty uncommon. It is counterintuitive to most clinicians, but the scientific evidence is clear that having a mental health disorder does not increase the risk of frequent cannabis use. Additionally, the evidence is clear that mental health treatment is much less effective with ongoing cannabis use and likely not effective at all, unless cannabis use declines. I also created the presentation because I would get a referral to see patients for depression, anxiety, or ADHD with no mention of frequent cannabis use in the chart.
There are also good studies that this trend toward increasing potency is associated with increased negative consequences [such as] quicker time to dependency.
Voorhees: Some signs of cannabis overconsumption include paranoia, confusion, and increased heart rate. If you think someone might be experiencing an alcohol or other drug emergency, it’s important to get help immediately. The BU Good Samaritan Policy helps students get help without being afraid [of being disciplined].
The evidence is clear that mental health treatment is much less effective with ongoing cannabis use and likely not effective at all, unless cannabis use declines.
BU Today: What advice would you give now to students using cannabis?
Voorhees: Some strategies for using cannabis in a safer way include:
- Consider products with lower THC. Seek products with more balanced levels of THC and CBD [cannabidiol, the second most widespread cannabis ingredient];
- Use products from a reputable source. Know and understand where your cannabis is from. Cannabis from unregulated markets may contain unknown substances;
- Go slow. Give your body time to feel the effects. Edibles can take hours to kick in, so consuming more too soon can lead to an undesirable experience;
- Avoid mixing cannabis with other substances. Combining cannabis with other substances can increase the risk for harmful effects;
- Take tolerance breaks. If you seem to need more THC to feel the same effects, consider taking a break to help lower your tolerance.
Lally: As a psychiatrist, I try to focus my comments to those using cannabis frequently and having mental health distress. If a student walks in for mental health services, which implies they are having a problem, and they are using cannabis frequently, I share the info about the negative impacts of cannabis, and I encourage decreasing frequency of cannabis. The most common outcome of this, believe it or not, is that the student comes in for the next appointment and has stopped using altogether.
BU Today: Do many students buy into the misconception that, as one media report puts it, “the highest high is the best high?”
Lally: I have never heard a college student telling me that they are seeking the highest high or indicate that the potency of the THC matters to them. I have heard of this concept in other settings and with other substances—i.e., opioids—but never with cannabis in a college health setting. It does seem likely that consumer preference probably is a factor in the increased concentration in THC, but this has never come up with a student.
Students in or seeing a medical emergency on the Charles River or Fenway Campuses can call the Boston University Police Department at 617-353-2121. Medical Campus students can call BU Public Safety at 617-358-4444. If you’re off campus, call 911.
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