Name: Is marijuana bad for your brain? - Anees Bahji
Uploaded: 2019-12-08T10:54:17.000Z
Duration: 6 min 44 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

In 1970, marijuana was classified as a schedule 1 drug in the United States.

The strictest designation possible, meaning it was completely illegal and had no recognized medical uses.

For decades, this view persisted and set back research on the drug's mechanisms and effects.

Today, marijuana's therapeutic benefits are widely acknowledged, and some nations have legalized medical use or are moving in that direction.

But a growing recognition for marijuana's medical value doesn't answer the question, "Is recreational marijuana use bad for your brain?"

Marijuana acts on the body's cannabinoid system, which has receptors all over the brain and body.

Molecules native to the body, called endocannabinoids, also act on these receptors.

We don't totally understand the cannabinoid system, but it has one feature that provides a big clue to its function.

Most neurotransmitters travel from one neuron to the next, through a synapse to propagate a message.

But endocannabinoids travel in the opposite direction.

When a message passes from the one neuron to the next, the receiving neuron releases endocannabinoids.

Those endocannabinoids travel backward to influence the sending neuron, essentially giving it feedback from the receiving neuron.

This leads scientists to believe that the endocannabinoid system serves primarily to modulate other kinds of signals—amplifying some and diminishing others.

Feedback from endocannabinoids slows down rates of neural signaling.

That doesn't necessarily mean it slows down behavior or perception, though.

For example, slowing down a signal that inhibits smell could actually make smells more intense.

Marijuana contains two main active compounds, tetrahydrocannabinol or THC,  and cannabidiol, or CBD.

THC is thought to be primarily responsible for marijuana's psychoactive effects on behavior, cognition, and perception, while CBD is responsible for the non-psychoactive effects.

Like endocannabinoids, THC slows down signaling by binding to cannabinoid receptors.

But it binds to receptors all over this sprawling, diffuse system at once, whereas endocannabinoids are released in a specific place in response to a specific stimulus.

This widespread activity coupled with the fact that the cannabinoid system indirectly affects many other systems means that each person's particular brain chemistry, genetics, and previous life experience largely determine how they experience the drug.

That's true much more so with marijuana  than with other drugs

that produce their effects through one  or a few specific pathways.

So the harmful effects, if any, vary  considerably from person to person.

And while we don't know how  exactly how marijuana

there are clear risk factors that  can increase peoples' likelihood

In people younger than 25, cannabinoid  receptors are more concentrated

in the white matter than in people over 25.

The white matter is involved in  communication,

Frequent marijuana use can disrupt  the development of white matter tracts,

and also affect the brain's ability to  grow new connections.

This may damage long-term learning  ability and problem solving.

For now, it's unclear how severe this  damage can be or whether it's reversible.

And even among young people, the risk  is higher the younger someone is—

much higher for a 15 year old than a  22 year old, for instance.

Marijuana can also cause hallucinations  or paranoid delusions.

these symptoms usually subside  when a person stops using marijuana.

But in rare cases, psychosis  doesn't subside,

instead unmasking a persistent  psychotic disorder.

A family history of psychotic disorders  like schizophrenia is the clearest,

though not the only,  risk factor for this effect.

Marijuana-induced psychosis is also  more common among young adults,

though it's worth noting that  psychotic disorders

usually surface in this age range anyway.

What's unclear in these cases  is whether the psychotic disorder

would have appeared without  marijuana use—

is a catalyst for a tipping point that  wouldn't have been crossed otherwise,

or whether the reaction to  marijuana is merely an indication

In all likelihood, marijuana's role varies from person to person.

the brain and body become less sensitive  to marijuana after repeated uses,

meaning it takes more to  achieve the same effects.

there's no risk of fatal overdose  from marijuana,

and even heavy use doesn't  lead to debilitating

or life-threatening withdrawal  symptoms if use stops.

There are more subtle forms of  marijuana withdrawal, though,

including sleep disturbances,  irritability, and depressed mood,

which pass within a few weeks  of stopping use.

But while some risk factors are easy to  identify, others aren't well understood—

which means there's still some possibility of experiencing negative effects,

even if you don't have any of  the known risk factors.