Marijuana potency hit record levels in more than 30 years, posing greater risks to people who may consider the drug as harmless, a U.S. report unveiled on Thursday.

Marijuana comes from a plant called “Cannabis sativa.” The chemical found in this plant that produces the altered states of consciousness is called “delta-9-tetrahydrocannabinol” or “THC.” Whether smoked as a cigarette, or cooked into baked goods like brownies or cookies or brewed like a tea, marijuana use causes: relaxation, reduced coordination, reduced blood pressure, sleepiness, disruption in attention, an altered sense of time and space. In high doses, marijuana can also cause hallucinations, delusions, impaired memory and disorientation.

The study by the University of Mississippi’s Potency Monitoring Project examined the average amount of THC in samples seized by police and customs in the U.S. from 1975 through 2007 and found that the average amount of THC was 9.6 percent in 2007, compared with 9.75 percent the previous year and just fewer than 4 percent in 1983.

John Walters, director of the White House Office of National Drug Control Policy said the report highlights the importance of getting marijuana off the list of harmless drugs, citing risk of psychological, cognitive and respiratory problems, besides the risk of becoming addicted, CNN reports.

White House Office of National Drug Control Policy attributes marijuana’s potency to sophisticated growing techniques used by drug traffickers in the U.S. and Canada.

Marijuana is one of the world’s most commonly used illegal drugs. There are approximately 300 million users worldwide and 28 million users in the United States alone.