and this is the map of a brain on psilocybin,

the psychoactive compound in magic mushrooms.

All those new connections you can see

don't just make people trip.

They're also the reason that psilocybin

is one of today's most talked-about drugs

in certain medical circles.

Worldwide, more than 180 species of mushrooms

produce psilocybin, likely as a defense strategy.

Scientists believe that psilocybin

may dampen the appetite of predatory insects like ants

so that they feel full long before eating their way

through the entire mushroom.

Humans, on the other hand, well, they trip.

Johnson: Psilocybin is a so-called classic psychedelic,

so it's in the same category as drugs like LSD

and works in the brain in basically the same way.

Narrator: When you take psilocybin, your gut converts it

into another chemical, known as psilocin,

which binds to serotonin receptors called 2A,

and experts think that's what triggers

what they call neuronal avalanching.

It's essentially a domino effect

of different changes in the brain.

You've got increased activity in the visual cortex,

which leads to changes in your perception,

and then decreased network activity

in the default mode network, which leads to a loss of ego.

Johnson: And that may be why people often report

at high doses

a profound sense of unity, transcending beyond themselves.

Narrator: But perhaps most importantly,

psilocybin increases connectivity

among different regions of the brain.

Johnson: Because of that receptor activation,

there is a profound change

in the way that different areas of the brain

synchronize with each other.

Narrator: Think of it like an orchestra.

Normally, the brain has different musical groups

that each play independently.

Johnson: A sextet there, here's a quartet there.

This one's playing jazz. This one's classical,

and a number of other ones.

Narrator: But once psilocybin enters,

it's like you suddenly have a conductor.

Johnson: So there is this communication between areas

that are normally kind of compartmentalized

and doing their own thing.

Narrator: Scientists believe that it's a combination

of these effects that make psilocybin so useful

for combating depression and addiction.

When new areas in the brain start talking to each other,

for example, you might have new insights into old problems.

And that's why some experts describe tripping

as a condensed version of talk therapy.

And then dissolving your ego, Johnson says...

Johnson: Can be profoundly healing.

Narrator: And there's actually an increasing amount

of research to prove it.

In two studies published in 2016,

researchers gave cancer patients with depression

a large dose of psilocybin, and even six months later,

at least 80% of them showed significant decreases

in depressed mood.

And research on addiction is equally promising.

In a study led by Johnson, 15 volunteers took psilocybin

to quit smoking, and after six months,

80% of them had kicked the habit,

compared to a rate of about 35%

for the drug varenicline, which is widely considered

the best smoking-cessation drug out there.

Yet despite these results,

psilocybin is still listed as a Schedule I drug,

a category reserved for compounds

that have no currently accepted medical use

and a high potential for abuse.

Now, taking magic mushrooms recreationally

does come with some risks.

Johnson: So a dramatic example would be

driving under the influence of psilocybin

or using it in a way that interferes with your job,

or your family relations, or your schoolwork, for example.

Narrator: But as far as scientists know,

long-term use doesn't damage the brain

in the way that other drugs can,

and according to at least one study,

it's actually the safest drug out there.

In 2018, for example, just 0.3% of people

who reported taking them needed medical emergency treatment,

compared to 0.9% for ecstasy and 1.3% for alcohol.

Taken altogether, that's why some states

across the country have campaigned

to decriminalize psilocybin, including Denver,

which, in May of 2019, became the first ever to succeed.