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Davis, California

Saturday, May 25, 2024

Blunt data reveal higher truths about marijuana

On Nov. 2, Californians will vote on Proposition 19. The proposition will legalize the recreational use of marijuana and give state government the power to regulate and collect taxes on marijuana-related activities.

Rumors about the physical effects of marijuana persist. But how many of those rumors have actually been supported by scientific research?

The reported effects of cannabis use come down to two main chemicals in the plant: tetrahydrocannabinol (THC) and cannabidiol (CBD). THC is the active ingredient responsible for the classic “high.” These effects include euphoria and hyperactivity but also anxiety and paranoia. CBD has more calming effects. “Skunk-type” strains of cannabis contain higher ratios of THC to CBD.

According to a 2010 study from the University College London, the high THC “skunk” strains led to higher risk of memory impairment than the higher CBD strains.

Marijuana intoxication can cause distorted perceptions, impaired coordination as well as problems with learning, memory and problem solving. Research shows that the degree of adverse effects on memory and learning depends on the dosage.

Harold Kalant, professor emeritus of pharmacology and pathological chemistry at the University of Toronto, noted a direct correlation between the harmful effects of marijuana and amount consumed.

“Cannabis is not a terribly dangerous drug compared to others, but it depends on how much you use, and there is very strong evidence that you can use enough to have harmful effects,” Kalant said.

The scientific journal Archives of General Psychiatry published an article in 2001 on neuropsychological performance in long-term cannabis users, showing that marijuana’s adverse impact on learning and memory can last for days or weeks after the “high” wears off. Someone who smokes marijuana every day may be functioning at a lower intellectual level all the time.

Kalant said that for those who smoke every day, the cannabis accumulates over time, and causes more severe harmful effects on memory, learning and problem solving.

In a 2007 study published in the Western Journal of Medicine (WJM), marijuana smoke contains 50 to 70 percent more carcinogenic hydrocarbons than are in tobacco smoke. Marijuana users usually inhale more deeply and hold their breath longer than tobacco smokers do. Doing this increases the lungs’ exposure to harmful smoke.

According to the WJM study, marijuana smokers can have many of the same respiratory problems as tobacco smokers, such as daily cough and phlegm production, more frequent acute chest illness and a heightened risk of lung infections.

WJM also published a 1993 study on long-term marijuana users. According to this report, marijuana smokers reported more days ill with a cold, flu or sore throat in the past year.

“Whether the smoke can cause cancer or not is still not clear … but it does produce precancerous changes,” Kalant said.

Precancerous cells can develop from inhalation of marijuana smoke, but in 2006, UCLA conducted a research experiment confirming that no link exists between the use of marijuana and development of any type of cancer.

A major issue in the marijuana debate is the addictive agents in cannabis. According to many studies, those trying to quit smoking do undergo withdrawal effects. Long-term marijuana users trying to quit report irritability, sleeplessness, decreased appetite, anxiety and drug craving. These effects make it difficult to quit and according to Kalant, occur in 10 percent of marijuana users – the same percentage seen in alcohol users suffering from addiction.

George Patton, director of Adolescent Health Research at The Royal Children’s Hospital Melbourne, confirmed the addictive potential in marijuana.

“There is a definite addiction syndrome associated with heavy cannabis use,” Patton said. “Cessation in these users tends to be accompanied by feeling out of sort, irritable and having difficulty sleeping and relaxing; symptoms that are alleviated by using again.

Data also shows that those who start smoking marijuana regularly in adolescence have twice the likelihood of developing mental illness, most commonly schizophrenia. For those already diagnosed with mental illness, use of marijuana greatly heightens their symptoms.

Barth Wilsey, professor of anesthesiology at UC Davis, commented on the effects of marijuana on mental illness.

“With bipolar disorder, they spend more time in mania, and with schizophrenia they experience a higher rate of suicide. Both are mental illnesses that manifest in college-age students,” said Wilsey.

Differences in dosages have different effects, and researchers are still working to figure out marijuana’s real impact on health.

“Marijuana is not anything magic,” Kalant said. “It obeys the same general laws that all drugs do. Like any other drug acting on the nervous system, it can produce effects with varying degree according to how much you take.”

CAMMIE ROLLE can be reached at science@theaggie.org.


  1. Cammie Rolle did you get your FACTS for your research out of REEFER MADDNESS.Research NEW STUDIES PLEASE it is a wonderful drug and is HELPING MILLIONS of SICK PEOPLE as I type this. Please check out wamm.org


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