The Science of Marijuana: How THC Affects the Brain

Some people believe smoking marijuana carries no risks. But scientific research shows that there are risks, especially for teens. Marijuana affects a person’s judgment and can impair his or her ability to drive. For those who use it regularly, it can lead to poor academic performance, or even addiction.

So how does marijuana have such a big impact on a person’s ability to function?

Scientists have asked themselves that question for a long time. And after several decades of research they not only figured out how marijuana works, but scientists also discovered an important communications system in the brain and the body, which they called the endocannabinoid system after the cannabis plant from which marijuana comes.

“Endo”—what?
Understanding the science of marijuana began in the mid-1960s with the identification of THC (delta-9-tetrahydrocannabinol) as marijuana’s main active ingredient. Twenty years later, scientists identified the sites in the brain and body where marijuana acts and called them cannabinoid (CB) receptors.

Scientists then discovered the body’s own natural chemicals—anandamide and 2-AG (2-arachidonoyl glycerol)—which also act on CB receptors. These chemicals (called cannabinoids), along with their receptors, make up the endocannabinoid (EC) system.

The EC system is found in many areas of the brain, which explains why it affects so many different body functions. Cannabinoids exert their influence by regulating how cells communicate—how they send, receive, or process messages. Cannabinoids act like a type of “dimmer switch,” slowing down communication between cells.

So how does THC affect the EC system?
When someone smokes marijuana, THC gets into the brain rapidly and attaches to cannabinoid receptors. The natural EC system is finely tuned to react appropriately to incoming information. But THC overwhelms the EC system. It prevents the natural chemicals from doing their job properly and throws the whole system off balance