How does marijuana affect brain function?

Brain function depends on a complex interplay of chemicals known as neurotransmitters that act as carriers of information between cells called neurons. Tetrahydrocannabinol (THC), which is the main active ingredient in marijuana, affects this interplay by altering the strength of some of these signals. THC also interferes with the normal communication between neurons and between brain circuits.

THC specifically interacts with brain proteins named cannabinoid receptors that are highly expressed in the brain. A higher density of these proteins exists in brain areas that are critical for learning, memory, pain perception, and reward processing. In fact, scientists think the activation of cannabinoid receptors in the brain’s reward pathways may underlie marijuana’s likelihood for abuse.

Despite the promise of medicinal cannabinoid drugs, concerns remain regarding the effects of marijuana on the developing brain. Marijuana abuse during adolescence may produce enduring changes in brain function, particularly in individuals at a greater risk for developing psychiatric disorders. Scientific research suggests that repeated marijuana use during adolescence (at least four joints per week) can increase the risk for psychosis, decrease adulthood IQ, and lead to changes in the brain that increase vulnerability to more dangerous illicit drugs.

Marijuana’s medicinal and addictive properties have prompted the search for new drugs that exhibit a reduced potential for abuse while retaining therapeutic value. The recent discovery that the brain naturally produces chemicals targeting cannabinoid receptors has opened new avenues for drug discovery. Indeed, promising new studies show that drugs targeting the brain’s natural cannabinoid system may offer relief to patients suffering from debilitating conditions such as chronic pain, obesity, and mental health disorders.

About the Author

Joseph Cheer

Joseph Cheer is an associate professor of anatomy, neurobiology and psychiatry at the University of Maryland School of Medicine. His research is aimed at understanding the functions of the endogenous cannabinoid system, with a special emphasis on its interactions with brain reward pathways.