Lecture Notes on Marijuana and Brain Effects

Introduction to Marijuana Classification

In 1970, marijuana was classified as a Schedule 1 drug in the U.S.
- This means it was completely illegal and had no recognized medical uses.
For decades, this classification hindered research on marijuana's mechanisms and effects.
Today, marijuana’s therapeutic benefits are widely acknowledged.
- Some nations have legalized medical use or are moving in that direction.

Growing recognition of marijuana’s medical value raises the question:
- Is recreational marijuana use bad for your brain?

Marijuana acts on the body’s cannabinoid system.
- Cannabinoid receptors are found throughout the brain and body.
Endocannabinoids (native molecules) also act on these receptors.
The cannabinoid system is not fully understood but has a unique feature:
- Endocannabinoids travel backward to provide feedback to sending neurons.
- This feedback modulates signals, amplifying some and diminishing others.

Endocannabinoids can slow down rates of neural signaling.
- This does not necessarily slow behavior or perception.
  - Example: Slowing a signal that inhibits smell can intensify the smell experience.

Two main active compounds:
- Tetrahydrocannabinol (THC): Responsible for psychoactive effects (behavior, cognition, perception).
- Cannabidiol (CBD): Responsible for non-psychoactive effects.
THC binds to cannabinoid receptors widely, unlike endocannabinoids which are localized.
Individual experiences with marijuana vary based on:
- Brain chemistry
- Genetics
- Previous life experiences

Harmful effects of marijuana may vary significantly among individuals.
Age:
- Clear risk factor; more cannabinoid receptors in the white matter of those <25 years old.
- White matter is crucial for communication, learning, memory, and emotions.
- Frequent use can disrupt white matter development and neural connections.
- The risk is higher the younger the individual (e.g., a 15-year-old vs. a 22-year-old).
Psychosis:
- Marijuana can cause hallucinations or paranoid delusions (marijuana-induced psychosis).
- Symptoms often subside after stopping use, but in rare cases can reveal persistent disorders.
- Family history of psychotic disorders (e.g., schizophrenia) is a key risk factor.
- Uncertainty exists about whether marijuana triggers or exacerbates these disorders.

With repeated use, the brain and body become less sensitive to marijuana.
Unlike many drugs, there is no risk of fatal overdose from marijuana.
Heavy use does not lead to debilitating withdrawal symptoms.
Subtle withdrawal forms include:
- Sleep disturbances
- Irritability
- Depressed mood
- These effects generally pass within weeks after cessation.