The hippocampus is a seahorse-shaped structure in the body’s limbic system associated with emotions and memories. More importantly though, the hippocampus is the brain’s storage center for one’s conscious, explicit memories.

However, how would external substances impact the function of the hippocampus? Drugs such as methamphetamine and cocaine have been heavily documented for their deleterious effects on the human body, but certain drugs — including cannabis/marijuana — have not been deemed as particularly harmful. With cannabis legalization becoming more widespread in the United States as a pain reliever, scientists have explored how the compounds inside marijuana may impact the hippocampus, yielding undesirable effects.^[9]

The location of the hippocampus in the brain. Link

The brain's chemical's structure (Anandamide) vs THC's chemical structure

Marijuana contains a chemical compound known as 9-delta-tetrahydrocannabinols (THC) that generates a pleasurable sensation.^[11] THC is no new discovery; scientists extracted it from plants as early as the 1940s.^[10] Regardless, because of increased marijuana usage amongst the general public, scientists are still frequently making new discoveries of the compound’s effects on the hippocampus.

THC is incredibly potent because our body possesses its own endocannabinoid system (ECS); the ECS comprises a vast network of chemical signals and cellular receptors that are densely packed throughout our brains and bodies. The cannabinoid-1 receptors (CB1) in the central nervous system (CNS) — meaning the brain and spinal cord — outnumber many of the other receptor types on the brain. They are the "traffic cops" that monitor the levels and activity of many other neurotransmitters. To stimulate these receptors, our bodies produce lipid neurotransmitters called endocannabinoids, which are structurally similar to molecules in the cannabis plant. When endocannabinoids bond with CB1 receptors, the brain receives a signal to release dopamine, the "pleasure chemical." (The first endocannabinoid that was discovered was named anandamide after the Sanskrit word ananda for bliss). Simply put, we all possess tiny cannabis-like molecules swimming around in our brains.

The cannabis plant, which humans have been using for about 5,000 years, hijacks this cellular machinery. The brain's anandamide (C₂₁H₃₀O₂) and marijuana's tetrahydrocannabinol (C₂₂H₃₇O₂) compounds have very similar chemical structures; the two are very similar in molar mass and contain nonpolar regions (C-H) and polar regions (C-O), allowing both to interact with the CB1 receptor’s active site to trigger the release of dopamine.

With THC binding to the brain’s cannabinoid receptors, it competitively inhibits the binding of anandamide to the CB1 receptor. While triggering the release of dopamine, it "crowds out" natural endocannabinoids from binding to the CB1 receptors.

First and foremost, THC's binding to CB1 receptors disrupts the flow of information and feedback between neurons.

Further, THC signals the brain to release a significantly larger amount of dopamine than anandamide does, creating a significantly more pleasing experience for the cannabis user. As a result, the human brain signals the body to produce fewer natural endocannabinoids on its own, resulting in the cannabis becoming more and more responsible for the brain's pleasure and thus resulting in users consuming them in greater quantities.

When THC consumption is reduced, effects wane, resulting in the human body lacking an appropriate amount of endocannabinoids. This effect — which only occasionally occurs — is called cannabis withdrawal syndrome , or CWS.^[1]