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Secret Side Effects of Smoking Marijuana Daily, According to Science

Here’s what doctors want you to know.
FACT CHECKED BY Emilia Paluszek

Marijuana is legal in several US states now (although still illegal at the federal level)—but how much do we know about the long-term effects of daily use? "We know a lot more about both the benefits and the risks of cannabis use, although I would say that the rate and scale of research has not kept pace with the interest," says Kevin Hill, MD, MHS, associate professor of psychiatry at Harvard Medical School and director of the Division of Addiction Psychiatry at Beth Israel Deaconess Medical Center. "There is a growing body of literature on the therapeutic use of cannabis and, similarly, we're learning bits and pieces about the problems associated with cannabis use. But our increased knowledge pales in comparison to the intense public interest, so one of the issues we often encounter is a growing divide between what the science says and what public perception is." Here are five possible side effects of smoking marijuana every day, according to experts. Read on—and to ensure your health and the health of others, don't miss these Sure Signs You've Already Had COVID.


You Can Become Addicted

Female GP giving medical marijuana oil to patient.

Cannabis is addictive, experts warn, despite what people might think. "You can become addicted to cannabis, though most people don't," says Dr. Hill. "Yet invariably, when people hear about what I do, they say, 'Oh, you're an addiction psychiatrist? Well, cannabis is not physically addictive; it's psychological.' So there are fallacies about cannabis. And they continue because people are invested in trying to get people to vote one way or another on issues like medical cannabis or legalization of recreational cannabis. It's less addictive than alcohol, less addictive than opioids, but just because it's less addictive doesn't mean that it's not addictive."


Depression and Anxiety

Thoughtful girl sitting on sill embracing knees looking at window, sad depressed teenager spending time alone at home, young upset pensive woman feeling lonely or frustrated thinking about problems

"When we talk about the harms of cannabis, young people using regularly can have cognitive problems, up to an eight-point loss of IQ over time," says Dr. Hill. "It can worsen depression. It can worsen anxiety. But all of those consequences depend upon the dose. The data that shows those impacts look at young people who are using pretty much every day."


You Could Get Very Sick

young woman with nausea in all denim outfit sitting on bed
Shutterstock / New Africa

"One particular condition to be aware of is cannabinoid hyperemesis syndrome (CHS)," says Jedidiah Perdue, MD, medical director at Arcadia Trails INTEGRIS Center for Addiction Recovery. "This highly unpleasant illness involves cyclical vomiting triggered by frequent use of cannabis. Nausea is pronounced and may abate temporarily with a hot shower. Fortunately, this syndrome improves upon stopping cannabis."


Memory Issues and Schizophrenia

Sacred mature woman.

Long-term marijuana use can impact memory, doctors say. "Chronic use of cannabis has been associated with deficits in verbal memory, which may persist even after stopping," says Dr. Perdue. "There is also a risk of psychiatric disorders, including schizophrenia, most pronounced among adolescents with genetic risk factors and those using highly-potent forms of cannabis."


Impact on IQ

Female driver sits at wheel in car, touches her head.

There is evidence that chronic marijuana use could affect intelligence. "The potential impact of regular cannabis use on intelligence has received a great deal of attention and has been a highly contentious topic of recent discussion," say Robert Gabrys, PhD, and Amy Porath, PhD. "In one longitudinal cohort study, early onset cannabis use was associated with a decline in intelligence (an average IQ decline of eight points) over the course of a 25 year period (age 13 to 38), and this relationship was independent of years of education. Among individuals who began using cannabis prior to the age of 18 and who subsequently were abstinent from the drug, IQ scores remained significantly lower compared to those who did not engage in regular use."

Ferozan Mast
Ferozan Mast is a science, health and wellness writer with a passion for making science and research-backed information accessible to a general audience. Read more about Ferozan