All language subtitles for BBC.Horizon.2009.Cannabis.The.Evil.Weed.HDTV.XviD.MP3.MVGroup.org

Cannabis...
It's merely a plant, a wild weed...

but it produces a range of effects
that is unmatched.

but it produces a range of effects
that is unmatched.

For some, it's a blissful release...

It is nice.

It is so nice. It is nicer than nice.

It is... I don't know if I
can say this on camera, but
it's almost as nice as sex.

While for others, it's something
that seems to have unravelled their
minds and emptied their lives.

I'm an addict and

I loathe myself, I really do.

I'm ruled by it, I'm ruled.

And I don't think it'll ever stop
until I'm dead.

I hear the voice
of a girl I used to know.

Sometimes she's told me to
commit suicide and things, but
I tend to just ignore it.

In this film, I want to get to the

bottom of this conflict by asking
the most basic questions
about cannabis.

Can it really cause schizophrenia?

The vulnerable group are
children under 15

receiving high doses or
concentrations of THC repeatedly.

Can it lead you to
take harder drugs?

You don't have enduring

biological changes that occur
because of the cannabis exposure.

Or,
could cannabis even be good for you?

With all the publicity around
the link with cannabis smoking
and the potential of increasing

the risk of psychosis, here we
have a component of the plant
which itself is anti-psychotic.

The science is so often
obscured by opinion

but what
does the latest research reveal
about the world's favourite drug?

In my job as a psychologist,
I deal with addiction.

I work with people with heroin
and crack cocaine dependence.

But with heroin and crack cocaine..

I regularly see people
brought to their knees, lives
ruined, even deaths.

But by comparison,
for cannabis, it seems to me the
effects are like a walk in the park.

And yet this is the one drug
that's rarely out of the public eye,
and shrouded in controversy.

And that's because more people
use cannabis than all other
illicit drugs put together.

According to a United Nations
report,

almost one in 20 adults across
the globe uses it each year.

Of the people
watching this programme,

one in three will have tried it,
and thousands will be smoking it
now.

I've tried cannabis.
I've smoked it a few times.
And yes, I've inhaled.

Did I like it? Not really.

I was giggly, and having said
that, though,
I felt a bit uneasy and

a bit behind the conversation,
a bit thick, to be honest.

And it wasn't really for me.

But I can see the attraction, I
can see that feeling out of control,

relaxed and enjoying
the flow of a conversation

would be, for many people,
a good thing to do.

But I want to know why one simple
weed has such a profound impact
on all our lives.

The story of the cannabis plant
begins 50 million years ago,
in an unexpected place.

This is Kazakhstan.
I'm hoping to find out

why this psychoactive plant might
have evolved here, of all places.

Professor Kanat Sarsenbaev
is Kazakhstan's national
cannabis expert.

He takes me to the nearby
mountains to explain.

So here we are
in the Tian Shan mountains.

Is this the origin of cannabis?

I think so,

because cannabis evolved in this
place many million years ago,

After evolving, it distributed
through the Tian Shan chain
to China.

After this, to all the world.

The Tian Shan mountain
chain stretches 2,500km,
reaching into China and Pakistan.

While it's hard to
know exactly where

along this chain cannabis evolved,
what it evolved from is clear.

Cannabis is a close
relative of the hop plant,
but with one crucial difference.

Cannabis contains
a chemical called THC,
tetra-hydro-cannabinol,

the active ingredient,
which gets you stoned.

Here we are.

We're in the mountains here and it's
not in great abundance but here it
is, here's a specimen of cannabis.

This plant has been here for
millions of years but
what I don't understand is why

would this plant have evolved THC,
this psychoactive compound. What was
the reason for the cannabis plant?

I consider that accumulation of THC
gives a lot of privilege to cannabis.

This plant very resistant to
ultra-violet. Extremely.

So it's a defence against
ultra-violet light at this altitude?

Another thing, the taste of the
leaves.. you can taste if you want.

I'll have a little bite here.
Yes, it's not so good.

Oh, yeah, that's really bad.

Yes, cattle consider the
same and they don't eat leaves and

plant during the vegetation period.

So just like any other plant,
cannabis evolved defences
to enable it to survive.

It just so happens that in the
case of cannabis, these defences
took the form of the chemical, THC.

But the reason why THC gets
you stoned is due to another,

entirely unrelated
accident of evolution.

The origins of our response to
cannabis strangely preceded
the existence of the plant...

..and can be traced back millions
of years to primitive creatures
living in the ancient oceans.

And those creatures still exist
today, in the more familiar waters
of Portsmouth.

What we're looking for are
some buoys, or a boat that
has been here a while,

and maybe on the underside we'll see
hanging off the bottom of the buoy
hundreds of these creatures.

In a minute we can take
a look with a camera,

so if I just set that up
now as we're coming here.

Shall I grab this monitor?
Yeah, grab the monitor.

You should hopefully,
as I go under the water

now start to see
one or two of the sea squirts.

Oh, yes! Let's go further down,
and you can see one

there right
now in the light. Can you see it?

Oh, yes, now I can see. Close-up.

And there's more here. There we are.

But what on Earth

does a sea-squirt have to do with
the way cannabis affects
the human brain?

Well, if we go back say 500 million
years ago to the oceans

that would have been
full of creatures like these

before there were fish and animals
with backbones in the sea.

We would find living in the oceans,
thriving, creatures such as these

sea-squirts, that we find here
on the marina today.

And they have within them,
very simple nervous systems

that operate in much the same way
that our nervous systems operate.

In all animals, the nervous system
is made of the same components -

large numbers of nerve cells
carrying electrical signals,

and wherever these cells meet,

the signal is passed from one cell
to a receptor in the next cell,

by a chemical messenger
called a neurotransmitter.

Across the brain there are different
types of these neurotransmitters

such as dopamine and serotonin.

All animals from donkeys to humans
have inherited this basic structure.

But way back in time,

the sea squirt evolved an
innovation to this system.

What happened was the nervous system
acquired a new chemical,

a chemical
if you like that had a new flavour,

a new type of chemical, and
it's this chemical that is related

in structure and a similar shape

to the chemical
that's found in cannabis.

Because of this similarity,

these new signals
came to be known as cannabinoids.

On this buoy here,

you can see quite a lot of them.
And, what's been found is

that these compounds,
the cannabinoid type compounds,

they affect the time it takes
for the siphon to close

in response to touch.

It in fact takes longer
for the siphon to close

when they've been exposed to these
cannabinoid compounds.

Once the cannabinoid receptor
evolved in the sea-squirt

then it was inherited by every other
vertebrate animal which followed

including us humans.

It was only a matter of time
before one of these creatures

would encounter the cannabis plant,

so that THC and the cannabinoid
receptor would meet.

Since it was here in East Asia
that cannabis first proliferated,

it was probably here that
that first meeting took place.

It's not really difficult
to imagine how it happened,

I mean no-one knows for sure

when THC and the cannabinoid
receptor first came together

but it has to
have been here in these mountains.

And whether it was
an animal who, hungry,

overcame the unpleasant taste and
had a good munch on a cannabis bush,

or it was a bird
flying around, or a rodent...

the first stoned animal
is lost to history.

In that very first stoned animal,

THC from the cannabis plant flowed
from its gut into its bloodstream

and was carried to its brain.

There, it met the cannabinoid
receptor evolved so many

millions of years earlier
in the humble sea-squirt.

And it just so happened to fit...

like a key in a lock.

It was inevitable that eventually

cannabis would meet
its perfect partner...us.

It's not known exactly when humans
started consuming cannabis,

but there's evidence
that it's been used in this region

for nearly three thousand years.

Nomadic tribes passing through
Kazakhstan would pick the plant

and then distribute it selling it
along the silk road and other ancient

supply routes, to China, to India

and to other countries to the west,
And in a way cannabis joined

the ancient commodities
of salt and tea,

and its progress from that point on
became unstoppable.

From 2700BC cannabis was used in
China, as a treatment for pain,

malaria and constipation.

From there, as it spread along trade
and slave routes, cannabis became

more closely entwined with human
history than any other illicit drug.

Despite the global and enduring
popularity of cannabis,

modern science is only just
beginning to comprehend its effects.

Here, just outside Washington DC,

scientists are trying,
for the first time,

to find the density and location
of the cannabinoid receptors

in the human brain.

Conducting the research
is Dr Garth Terry.

What stage are you at, what's
happening? We have our volunteer here

who is being put into the
scanner. First we have to make sure

his head's in the right position, so
he has this white mask on his face.

What are you injecting him with?

We're injecting him with the
radioactive drug,

it works like a dye.

It targets only the cannabinoid
receptors throughout the entire body

and we're imaging the
cannabis receptors in the brain.

So this drug will accumulate
in the brain

and we'll get a picture of where
those cannabinoid receptors are

and how dense they are
throughout the entire brain.

By mapping out where cannabinoid
receptors exist in the brain,

and in what density,

it should help shed light on the
role of the cannabinoid system

which scientists are only
just beginning to understand.

What would you say the function is
of these endo-cannabinoid chemicals?

They act like a dimmer switch
for other neurotransmitters,

like dopamine, when they're
released in large quantities.

You need to have a way
to turn down that signal,

sort of turn down the amount
of neurotransmitter released.

Why do these other chemical
messengers need regulating?

That's a good question.
If you have too much of a signal,

it can actually be toxic
to some brain cells.

Imagine the case in epilepsy.

A lot of message is getting across,
it's not being regulated

it's all garbled, it's being
sent all at once, in full force.

In cases such as epilepsy, too much
of a neurotransmitter is released,

flooding through the brain
and activating too many nerve cells.

But when the cannabinoid receptors
are activated,

they cause the nerve cells

to reduce the amount
of neurotransmitter they release.

In this way, the cannabinoid
system keeps the brain stable,

with levels of neurotransmitters
at a happy medium.

After five hours,
the scan is complete.

So Garth, have you
got the results in?

Yes, we finished our five-hour scan
and let me show you what we have.

So this is an image
from our subject from today.

The receptors are
highlighted in what colour?

In bright red. Well, any colour
you see, there are receptors,

and red is the really
dense areas, and you can see
there's a lot of red and yellow.

Green and blue are the really
not dense areas, where there are
not many receptors.

So they really are everywhere?
Yes.

They are the densest receptors
in the brain,

the most populated throughout
the entire brain.

Are they only in the brain or are
they in other parts of the body?

I can show you an
image of a whole body
scan we've done here, here's one.

Oh, my god, look at that.

You can see it goes right into
the brain, look how hot that is.

But there's also cannabinoid
receptors in the liver.

Look at the bone marrow,
the vertebral column, the ribs.

So how does what we're seeing
in this image relate to
the experience of using cannabis?

Well, look at the amount
of cannabinoid receptors
in the brain - a lot of them.

A lot of the effects of
cannabis use are in the brain.

Euphoria... As an anxiolytic,
it dissolves your anxiety or it
can even cause your anxiety.

So cannabis abusers
or cannabis users

talk about having this high,
this euphoria,

that's probably from some of
the deep structures in the brain.

Garth's research shows that
the cannabinoid system protects

the brain by regulating the other
neurotransmitters within it.

And the fact that it is so
widespread is reflected in
the range of sensations it brings.

I have one spliff, nice and relaxed.

Another one, more relaxed.

By the third I might start giggling.

I could do anything.
Right now I could run in this sand.

I could run in the sand
from here to the pier and back,

and probably just
barely have a sweat.

How to explain the coming up
bit I guess... It's just...

slipping in to a nice warm bath,
I think is the best way to...

At the end of the day,
slipping into a nice warm bath,

maybe a Jacuzzi going on,
few bubbles, little yellow duck.

It's just sort of that
sort of like, "aaah..."

That the cannabis plant should have
evolved to produce a chemical

that fits the
highly complex receptors

in our brain to cause these effects
feels like a wild coincidence.

But it's not as strange
as you might think.

There are hundreds of
thousands of plant species and
they create thousands of chemicals

and it would be just remarkable
if there wasn't one that didn't
interact with the human brain.

And they do, there's the opium
poppy and the tobacco plant,

and both of those act on the brain.

These plants can affect our body
chemistry because they're made of
the same building blocks as we are.

Cannabis is no exception.

Whether you like it or not,
each and every one of us

is fundamentally
wired to respond to cannabis.

So has it simply been
the victim of prejudice?

How real is
the dark side of cannabis?

It's like I married cannabis,

I never had a relationship
of me own except with cannabis.

That was my relationship...
with cannabis.

I did have chances in the past
but I blew it because
I married that thing.

I feel powerless over this drug,
I despise it.

I gave up on life ten years ago.
I thought...

that's me doomed now because I can't
stop this insidious addiction.

John, not his real name,
began his relationship
with cannabis in his early 20s.

It was 1991 and I got in
with the wrong crowd,

going to rave clubs and things.

Some of the lads would be smoking
spliffs and I wanted to fit in.

Everybody else was doing it,
even me mates round where
I grew up, they were all doing it...

and I thought, well, you know
just to join the club like, and...

But I got stuck with it,

it started to rule my life
and it was on my mind constantly,

and I knew there
was going to be a problem there.

Now, every day of John's life
is structured around cannabis.

This morning I've been up since
four o'clock

and I've smoked about six,
seven, eight spliffs, I don't know.

My usual day is sad, but true...

I'll get up in the morning
whatever time it may be.

I'll brew up, have a cup of tea,

have a cup of coffee,
spliff in between...

Then I might go out for a walk
round the park sometimes

or feed the birds and then I'll have
some more spliffs, cup of tea.

Then come the evening time,
seven o'clock,

I might have a couple of
glasses of wine, spliff, spliff.

Then I'll roll a spliff
which I'll smoke when I'm in bed.

And that's Groundhog Day.

And that happens
most days in the week.

And today is no exception.

Right now...

I have to be perfectly honest,
I want youse to go for a bit while

I skin up and make a spliff and then
perhaps come back in half an hour.

John can now barely imagine
life without cannabis.

I think to myself, if I stop,
if I stop, how am I going to
cope in the real world?

That's how I feel.
How am I going to function?

How am I gonna mix with people?
How am I gonna converse with people?

I'm not used to doing that.
I've spent 17 or 18 years
puffing away on cannabis.

It's like I'd have to
start all over again...

And I think it's too late now,
it's too late.

I've squandered my opportunities.

I'm an addict,
I loathe meself, I really do.

Listening to John, he sounds
like he needs cannabis to live.

It's undoubtedly an addiction, but
not in the same way as harder drugs.

Heroin users that I see, there's no
question really, that if they don't

take the drug on a regular basis,
they're going to be sick.

They're going to get
physical withdrawal symptoms

and those symptoms

are going to get worse and worse
unless they take more of the drug.

And that's I suppose, a classical
definition of physical dependence.

Cannabis is clearly
much more subtle.

It's not physical addiction,
in that if they stop, they're not
going to be physically ill.

But if they stop
they'll feel craving...

a strong need
to take the drug again.

That is psychological addiction,

and I don't think of it as a sort
of lesser cousin to physical
addiction, it's equally serious.

So while it can be very damaging,
addiction to cannabis is not
a physical process in the body.

Yet cannabis has been accused
of permanently changing
the brain in other ways.

Does cannabis somehow make us more
likely to abuse other, stronger,

drugs such as cocaine or heroin?

To answer that question,
scientists have turned to rats.

Their brain chemistry is similar
to ours, but unlike humans,

it's possible to give them cannabis
in controlled amounts

to see if this increases
their taste for heroin.

Dr Steve Goldberg has been
measuring the effects.

Well, in this room,
we've got two groups of chambers,

one either side.

We're working with rats

on this side that have had
a previous exposure to cannabis.

On the other side, the animals
are control animals that have not
had the exposure to cannabis.

And we're looking at the
differences between these two groups

in terms of how much
heroin they take

and how hard they work for it.

What does this individual rat
have to do here?

He's in a test situation,
a light comes on,

tells him that heroin's available.

In order to get the heroin, he has
to poke his nose through a hole,

and he gets a dose of heroin.

The flashing light is now
him receiving a dose of heroin.

He's just had a dose of heroin?
Yes.

Each group of rats,

those who have been exposed to THC
and the control group who haven't,

have the opportunity to take heroin

by poking their noses
against a dispenser.

The number of nose-pokes
or doses

that each rat takes
is measured automatically.

Steve then compares the results to
see whether the past exposure to THC

makes the rats more likely to
take more frequent doses of heroin.

So what results have you
found for this rat and for
other rats in his group?

We found that rats that had exposure
to cannabis in the past

will work for and obtain
more heroin each session

than the control rats that didn't
have the cannabis exposure.

Actually, that's quite
shocking that you found a connection

between cannabis and heroin.

The history of cannabis exposure
produces a tolerance-like effect

where they're less
sensitive to the drug

and that carries over to heroin,
so they need a bigger dose to get
the same effect.

Tolerance just refers to the
amount of a drug required to get
you high when used repeatedly.

It is not the same as addiction
or desire for a drug,

which is better measured
by the effort made to get it.

But if you then go on
and in both groups

and increase the number of times
they have to nose-poke to get

the heroin, in other words increase
the price for getting heroin,

then the two groups are the same.

Steve gradually increases
the number of nose-pokes required

for one dose of heroin.

As the workload rises, they reach
a point, around 75 nose-pokes

where both groups give up
and stop working for the heroin.

So with increased effort, the effect
between the two groups disappeared.

That's true.

This shows there's no difference
in the drive to get heroin

between rats who have had
cannabis and rats who have not.

So what's the human implication?

Basically, that you don't have
enduring biological changes

that occur because
of the cannabis exposure

that predetermine that you're
going to go on and become

addicted to other hard drugs.

It says it's more of a social
and historical thing that drives it.

As ever, the picture is more
complicated than a chemical
switch in the brain.

It seems it's more likely
to be your peer group

or life-stresses such as
unemployment or the
end of a relationship,

that lead people from
cannabis on to harder drugs.

Yet there's another accusation
levelled at cannabis.

That it triggers one of the most
severe of all mental disorders.

Permanent psychosis,
or schizophrenia.

This is our family.

This is Mark who's 28,

Natalie who's 25 this is Paul who's
19 and this is his twin, Melissa.

And, as far as we know,
none of them suffer from any
mental illness of any kind,

so we think it's probably
the cannabis which has caused
the difficulties with Paul.

Paul Floyd started smoking skunk,
one of the most potent
strains of cannabis,

four years ago at
the age of fifteen.

After a year, he started
to have strange experiences.

'At first when I heard the voices,

'I thought it was God talking to me,
and I had delusions about God'

and they were causing me
to believe that I was Jesus

and that I'd rise to heaven
and things if I took it.

I first started hearing them when
I was on skunk and then they began

to just start happening
in normal every day life, as well.

At first, Paul's parents were
confused by his behaviour.

It was a gradual change

which we didn't really recognise
for what it was, at the time.

So there were things
like staring very intently

at members of the family,
other people, weren't there?

Um, laughing to himself when
there was nothing to laugh about.

And some strange sort of body
posturing sometimes,

it's quite hard to describe,
like some strange sort of gestures.

Almost boxing at times, wasn't it?
Yes.

Quite peculiar, really.

After that, Paul's behaviour
changed rapidly, as over time,

twelve separate voices appeared
and gave him instructions.

'They used to tell me
to throw things away

'like I'd throw away
my CD collection.'

They were saying I should
bring about the downfall of, like,

the music industry
by throwing CDs away.

Other people would follow

through some sort of mind link
or something.

Sometimes the voices would
speak to Paul through
the radio or television.

From programmes like Coronation
Street, the characters would say

to clean things.

I had to buy a lot of cleaning
products and they had to be matching
in every room of the house,

matching colours, he got quite
distressed if they weren't
the same colours in each room.

I've got a shed full of mops
and buckets that he persuaded
me to buy when he was

very fixated on cleaning.

Yet even at this point,
Sheila and Dave didn't connect
Paul's behaviour with cannabis...

because they didn't even
know he was smoking it.

Innocently, every week,
we would give him an allowance...

Even then we didn't make the
link between how he was behaving

and the fact that he smoking
that necessarily, did we?

I know that sounds
probably a bit naive now.

It was only once Sheila and
Dave took Paul to a psychiatrist

that they connected his
problems with cannabis.

Paul was diagnosed
with schizophrenia,

and prescribed anti-psychotic
medication which he may have to
take for the rest of his life.

But although the connection between
Paul's cannabis use
and schizophrenia may seems clear...

it's extremely hard to demonstrate.

Proving the link between
cannabis and psychosis
is never going to be easy.

It's a bit like a chicken
and the egg situation.

Does the drug cause mental illness,

or is it that people
with mental illness
in some way seek out cannabis?

'One person trying to untangle
this puzzle is Dr Cathy Fernandes.'

Tell me, how are you
studying the link

between cannabis
and schizophrenia?

What we're really interested in

is the long-lasting effects
of cannabis.

We're using mice to do this
because we can control
when they have the cannabis,

what age they have it,
and for how long.

So this is the centre of your
experiment. What goes on here?

This is a behavioural task
called the Morris Water Maze.

It's a spatial memory task,
so we are looking at differences
in memory and learning.

They have to learn the location
of a hidden platform in the pool,

so here we have the platform that's
hidden below the level of the water.

The water's sort of opaque,
isn't it?

That's right, it hides
the platform under the water.

So really they have to learn to
navigate by using cues
or objects outside the room,

so if you look around the room,

we have various objects outside
the pool and these help
the animals to navigate,

so when they reach the platform,
they can look up
and try and locate themselves.

So we're looking at how fast and how
quickly they reach the platform,

and whether they can swim
in a straight direction
when they reach the platform.

So Cathy took two groups of mice.
The first group were exposed to THC

when they were juveniles,
equivalent to age 10 to 15 in
humans.

So we gave them something equivalent
to two or three joints a day...

And we treated them for
two weeks, when they were young,

then we stopped their drug treatment
we waited for them to grow up,
until they were adults,

about two months later.

so now we're ready to test them,
they're drug free,
don't have any THC on board now.

'The first mouse goes in.'

But what can a swimming
mouse tell you about psychosis?

We don't know if any normal mice
would ever have schizophrenia.

But we do know there are some
very important core features

of schizophrenia
we can study in animals.

One of those features
is a memory impairment.

We can look at that directly in
mice, using this sort of task here,

we can pick up differences in memory
after giving the mice cannabis.

You have to say, he doesn't
look as if he's remembered
the location of the platform.

You can see he's swimming around
but really not finding the location
of the platform.

If he does find it,
you'd have to conclude
that it was by chance, I think.

That's right. He has already been
swimming for a while so now I will
guide him to the platform location.

And there he is.

'Cathy repeats the memory
test with a squad of 12 mice,

'before moving on to a second group
of mice who received THC

'when they were slightly older,
equivalent to teenagers
aged 15 and over.'

And straight there.

That's right, so you see a much
straighter, a more directed action
to the one he found it much quicker.

'Once more twelve mice are tested
before Cathy compares the results

'of the two groups
against a control group.'

So this is the track data
that we have from the computer
system that we use,

it's able to give us really accurate
recording and measures...

not just the time it takes for the
mice to reach the platform,

but also how far they've swam,
the distance they've swam.

So the first mice we have here,
these are the black mice

that received THC when they were
very young adolescents,

and if you look at the track,
they're really swimming
all over the pool,

not in a very straight
pattern, and taking a long time
to reach the location.

So if we now compare to the mice
who received the THC when they were
teenagers or young adults,

you can see they really have learnt
the location of the platform,

so clearly giving THC
when you're an older age doesn't
seem to cause an impairment.

Can you quantify the
difference between the two?

We do find a very large
significant difference,

as much as 25% deficit in the
THC-treated young adolescent mice,

so we really are fairly sure that
there's a strong impact in giving

THC to young adolescents, there's
a lasting effect on their memory
performance when they're adult.

Could you translate that
to human development?

We think that would indicate the
vulnerable group are children

under 15 receiving high doses
or concentrations of THC repeatedly.

It's a worrying trend
because the number of children

who are now taking cannabis
is really on the rise.

So we know that in the UK at least,
40% of 15-year-olds
have tried cannabis already,

and this is the point at which they
might be developmentally vulnerable
to the effects of THC.

Cathy's research implies
that just a few years

can make a critical difference to
how cannabis affects your brain.

But for schizophrenia
to develop is rare.

The likelihood
of developing schizophrenia
in your lifetime is 1%.

Occasional cannabis use
can raise this to 2%

while heavy use might raise
the lifetime risk to 6%.

The problem is, anyone using
cannabis won't know whether they
are vulnerable until it's too late.

Now Paul is trying
to rebuild his life.

We're immensely proud of him.

The way he's got through things,
he's back at college...

We're really, really
proud of him, he's coped
amazingly well with it all.

I'm hoping to learn to drive
and possibly go to uni
and study further,

and I'd like to go to Africa and
build a school and things like that.

Despite stopping smoking cannabis
and starting medication,

the voices in Paul's head
have not left him entirely.

Now I hear the voice
of a girl I used to know -

I didn't know her very well,

but for some reason
she stuck in my head.

I hear her voice most of the day

and before I go to sleep
is the worst time.

Sometimes she's told me to
commit suicide and things

but I tend to just ignore that.

The thought that
he will always be hearing that

is really difficult to contemplate

because I can hardly imagine
what that must be like.

Paul's story
shows what long-term effects

cannabis might have
on the human brain.

Now, research into the short-term
effects of using cannabis

suggests that there may be a link
with schizophrenia here too.

The first studies of the immediate
effects of THC on the human brain

are now being made by
Dr Zerrin Atakan.

I really want to see how cannabis
does its effect,

especially in the brain,

because this is the most widely used
drug in the world

and we still know
not too much about it.

Especially how it works
in the brain.

Zerrin was particularly interested
in how THC can affect

the brain's internal control over
your behaviour and inner thoughts.

As you know,
when people smoke cannabis

sometimes they can have,
some of them,

have difficulty
in controlling their behaviour,

and that's why we chose a task
that could measure this.

And the task is called
response inhibition,

or how you stop yourself
from doing something,

or how you put the brakes on.

OK. Can you show me the task? Yeah.

When volunteer lies in the scanner,
this is what he sees.

He sees an arrow
pointing right or left,

and he is asked to press the
button right or left accordingly.

And then occasionally there will be
an arrow pointing upwards,

and he is asked
not to press the button.

So in a sense
he is asked to do nothing?

He is asked to stop himself from
pressing the button

and this was the particular bit of
the task that we were interested in.

And this is how we
put the brakes on...

So I guess that sort of braking

is the sort of control over behaviour
that we do all the time. Yeah.

So Zerrin gave this task to
volunteers, inside a brain scanner.

Each of them had received THC
equivalent to smoking one joint.

She then repeated the experiment
with a placebo for comparison.

What she was looking for
was the brain activity in each group

as they tried not to press the
button in response to the up arrow.

This is the average
of 15 volunteers.

And this is the placebo condition,

basically
this is the normal situation.

This is the normal brain
responding to that task.

As you can see certain areas
are looking red there

which are activated,
that is the pre-frontal cortex...

and this is what you would
expect in a normal situation,

when we are stopping yourself
from doing something.

This is the average
of again 15 people

this time who have
taken THC, cannabis.

And what you see, very clearly,
that in fact the normal areas

are not working,
there's no activity.

Zerrin believes that
the inactivation of these
frontal areas of the brain

which interpret our surroundings

might explain some effects of
cannabis such as paranoia.

If your brakes aren't on,
you might misinterpret

or you could maybe
see a shadow or hear a sound.

Normally you would say this is just
a branch or this is just the wind,

but if you already misinterpreting
what is going on,

you're not putting the brakes on,
you might interpret
that as someone following you.

So this is showing how cannabis
affects the brain.

And would that be a similar way

in which the brain of
a schizophrenic might be working?

Yes, there are similarities,
I agree,

especially if you think that
cannabis can affect people

in a way that they become suspicious

and same thing you see also
in people with schizophrenia,

that they can be over-suspicious
about their environment,

and again we know that this area
is a suspect area

in severe mental illness
like schizophrenia.

Zerrin's research is preliminary

but implies that when the brain
is under the influence of THC,

the effects can be similar
to those seen in schizophrenia.

It reinforces the idea
that smoking cannabis

can, in a small number of cases,
trigger the condition.

But cannabis has another face
entirely.

Here in California, people are
using it to improve their health.

Following a legal statute
called the Compassionate Use Act,

passed in 1996,
those with a medical problem

can obtain cannabis
from a high street dispensary.

There's quite a strong smell
of cannabis.

Oh look, look.

These are all edible forms of
cannabis, I guess -

green label cakes,
single shot cakes, triple-X cakes,

vegan chocolate chip,
vanilla brownie,

down here various forms of soda, tea
and so forth,

chocolate chip, vanilla,
rich berries, mango,

all cannabis ice-cream.

There's two condensed buds
of cannabis.

Oh, and look - a joint itself.

And here's
the centre of the operation,

and lo and behold it's a sort of
bank of cannabis there.

One of the people making medical use
of marijuana,

as it's known in the US,
is Allison Stanley.

When I started to look into this

I thought "No way,
this is just another gimmick,

"this is for potheads,
this is for druggies," you know,

"I don't want to get addicted".
I wasn't for it in the beginning.

But after exhausting
all conventional treatments,

she had to reconsider.

I was in a very serious car accident
last summer,

where I was shoved under the
dashboard, and I had a detached colon
as a result of it,

I had a knee injury,
I have a shoulder injury, and
I'm going through multiple surgeries.

And my doctors weren't able to
address the pain issue,

or the lack of sleep
that I was getting.

I keep it in my bedroom,
and only in my bedroom.

All you do is insert this...
and you do this.

It helps with the pain, definitely,

and it definitely helps me
sleep at night.

So it's brought life back to me.

Elsewhere in Los Angeles,
Tom is using medical marijuana

for entirely different reasons.

I smoke medical marijuana, cannabis,
because it makes me relaxed.

It helps me deal with
day-to-day stress in life.

It really helps me with anxiety,

and I have incredible
anxiety attacks

where I just get stressed out,
I can't deal with reality.

Previously I had a prescription
to anxiety drugs

and those anxiety drugs,
taking them so much

and it was just really,
really bad for me.

It was the strain
of the business world

that drove Tom to find a release.

The corporate world
made me stressed,

extremely stressed.

Totally stressed.

I am so happy I'm out of
the corporate world, it's amazing.

TOM COUGHS

I'm not very social
when I don't smoke marijuana.

I like smoking marijuana...
It calms me down.

I just feel totally at ease,
everybody knows me -

"Smoke a little marijuana, Tom,
you'll be great.

"Everything's gonna be fine,
you know. Take a hit!"

Usually I'll do that, just smoking
large quantities with other patients

and we're all medicating together,
collectively,

and so we'll do that
in more of a social environment

where we're medicating,
yet being social.

So it's not that we're socially
smoking the marijuana,

we're medicating it for use,
but we're doing it together.

For Tom and Alison, obtaining
cannabis is straightforward.

They go about it the same way as you
would obtain any other medicine,

by going to a doctor.

Alan, how does
your practice work here?

It works just like my internal
medicine office,

patients call in, they come in,
they're evaluated by myself,

I make a diagnosis

and if appropriate I recommend
medical cannabis for them.

What are some of the complaints
people come in with?

The common complaints are either
Chronic Pain Syndrome of some sort,

and that can be a specific
back or hip injury,

anxiety's a very common one,

depression, insomnia.

What proportion would you say come
in with the common mental health
disorders, anxiety and depression?

Probably anxiety, depression
represent about half the patients.

As many as that. Couldn't that
make their problems worse?

If somebody has mild daily anxiety,

they're just trying
to feel 25% better.

Is it reasonable for them to try
using a little plant extract,

if you look at it that way,
it's kind of hard to argue against.

It's just it's been built up
as being such a scary, scary thing.

And it just isn't.

What if I walked into your practice
on a Monday morning,

and I sat down and I said,

"Dr Frankel, my mood's good,
I don't have any pain,

"but you know what, I just can't seem
get over writer's block.

"I'm sitting at my PC
and I'm just not getting it

"and I've been stuck for a week,

"can you give me anything
for my creativity?"

I know that people would disagree
with it, with me for saying this,

but to me that's a reasonable,
I think, human right,

to try and improve your situation
by doing constructive things

under a professional's care.

And could that include cannabis?

Yes. In my opinion.

Would it be fair for me to think
that it doesn't really matter

what people come in with,
if they're the right age,

they've got general pain
or psychological problems,

the answer from Dr Frankel's
point of view is cannabis.

Yes, if I were a cardiologist
and patients were coming into me,

they'd leave with
cardiology medications.

If I'm a cannabiologist and they're
coming to me cos they've tried

so many other things
and they've failed,

the likelihood is they'll leave
with a cannabis recommendation.

While the system in place here
runs smoothly enough,

it worries me
that it's open to abuse,

but more than that,
it's an experiment

that is being stretched beyond
any available evidence.

I don't really have a problem
buying into the view

of cannabis as being connected
to treating pain,

you know, that seems
to be pretty clear.

Whether we can make
a much greater leap of faith

towards buying into the treatment
of common mental disorders

such as anxiety and depression
with cannabis

is a bigger order and I'm still
pretty sceptical about that.

To add to the uncertainty,

although medical cannabis is
approved by California state law,

it's still illegal
under federal law,

so even here where residents
have voted for medical cannabis,

the relationship is still
a confused one.

It's a surprising situation for a
plant that's been with us so long.

Other plant-based drugs
with medical uses,

such as aspirin, cocaine and heroin,

have all been exploited
for their full benefits.

But cannabis lags behind.

In fact only now is
the world's first legal medicine

based on the cannabis plant
being produced,

deep in the English countryside.

I'm going there for a rare glimpse.

Even though it's all done
completely legally,

with the permission
of the Home Office,

the security arrangements
means the exact location
has to remain a secret.

That means we're gonna have
to turn the camera off.

Come on through, John.
Thank you. So this is it?

This is it, you can see here,
one of our growing areas.

And a fairly wide selection
of plants.

Come on in, have a look. Thank you.

Gosh, there's loads of it!

How many plants have we got here?

There's about 5,000 plants here
and every year we grow about 30,000.

And how much volume of cannabis
would this produce per year?

The payload, the botanical raw
materials it's called, about a tonne.

Gosh.

To turn it into a saleable
pain relief medicine,

the cannabis is first dried.

Each and every plant is a clone,
so that the exact properties
are known and consistent.

It's like hanging out the washing.

let's go in here now.

After you.

We need to get into
this kit I'm afraid.

Next it is milled and heated... .

So we See raw material, will be

put into the

mill and its grounded down
to particals of about a millimeter.

At this stage nothing's wasted...

Yes, it all goes in there exactly.

The plant material is reduced to a
concentrate And then it ends up in

here, spinning down to about
60 degrees and all the
liquid just evaporates away.

To give you an idea of
the sort of material it is,

it's sort of treacle like.

It's quite sticky. It really is
quite sticky, and that makes it

quite hard to work with therefore.

Let's have a look at that.

Oh, gosh.

The final product is a liquid which
the patient sprays into their mouth

so removing the need
for harmful smoking.

Yet, despite this
meticulous processing,

it's still not widely available.

It's not exactly taking it's place

in the pharmacies
across the country.

Is that because
the effects are quite weak?

No, they're not weak at all.

I think that cannabis wouldn't
have survived over the millennia

as a medicinal...entity
if it had been weak.

And cannabis-medicines aren't weak.

It's simply that we're dealing
with a group of patients

who have tried all the standard
medicines and haven't responded

before they ever come
into the medical clinical
trials with this drug.

Dealing with outcome measures
which are really vague -

Pain and spasticity are very hard
to quantify in a research situation.

Despite this, so far,
the only available product

is a treatment for pain
caused by multiple sclerosis,

and this is licensed only in Canada.

But there's a possibility
of treating many more ailments

thanks to an unexpected
property of the plant.

If you look in
the microscope,

you can see some glistening
golfball-like structures.

And those are
the glandular trichomes

in the inflorescence of the plant

which contain the chemicals we're
interested in for making a medicine.

It's not just THC.

These trichomes contain CBD,
another valuable chemical.

There's a lot of CBD in
that particular one as well,
cannabidiol, another cannabinoid,

a non-psychoactive cannabinoid, an
important component to the medicine.

So, from your point of view, in
terms of developing medications,

cannabidiol, CBD,
what role does that have?

We hope it's gonna...
We're fascinated by this stuff,

which has tremendous potential
as an anti-inflammatory but
also as an anti-psychotic.

So you're telling me CBD
could be a treatment for psychosis?

Yes, isn't that ironic?

With all the tremendous
publicity around the link
between cannabis smoking

and the potential of increasing
the risk of psychosis,

here we have a component
of the plant which itself
is anti-psychotic.

And we're saying... Within the
same plant, you have a chemical

which has an opposite effect

and which therefore be protective
to some extent?

I think it's a level of concern

that some of the recreational
cannabis that's out there

contains no CBD at all
and that is a modern phenomenon.

Previously, it was much more usual
for people to be smoking cannabis

some CBD in it at least.

As recreational cannabis plants
are grown for higher THC content,

so their CBD content falls,

simply because the plant isn't able
to produce high levels of both.

So your trick,
as a developer of medication,

is, I suppose, to change the
relative balance of THC and CBD.

Exactly so... Getting that
proportion right for different
conditions is going to be key.

We think for pain and spasticity,
a roughly equal balance of THC

and CBD is good, because each has
their own type of pharmacology,

quite separate mechanisms
of action, and they interact
together in a helpful way.

Probably along with other
plant constituents too.

But for other conditions like
inflammation or psychosis,

you wouldn't want,
probably, any THC at all.

You'd want some of
the other plant components,

but you'd want the CBD mainly,
alongside those other components.

For a plant that's been
known and used medicinally
for almost 3,000 years,

it's surprising that new chemicals
and uses are still being discovered.

What I find even more surprising is
that the medicinal use of cannabis

is so far from being
widely accepted.

It seems to me that across the
world, our relationship with
cannabis remains confused.

And not without reason.

For many people, it brings
them a great deal of pleasure.

Unless you've actually tried it,
you can't say how good it feels.

All I know is that I feel
absolutely fantastic.

But all drug use comes
with a price.

It's like the old record says -
you reap what you sow.

And it's so true.

Because I'm reaping what I sowed,
and I regret it,
I've just wasted my life.

I've just let life pass me by
because I've been sat in the chair
just smoking cannabis.

From what I've seen,
unlike heroin and crack cocaine,
the drugs that I deal with

as a psychologist, cannabis
is just not in the same league.

It can't kill you, and it's
very unlikely to ruin your life.

But that's not to say
it's entirely safe.

Actually, I'm quite impressed
with how much evidence has been
gathered about the dangers.

It seems to me that cannabis has
no place in the developing brain.

And although the numbers of people
likely to be affected is tiny,

there does appear to be a link

between early use of cannabis
and mental health problems.

For our family, it's been
absolutely devastating.

Paul is still suffering the
effects, still hears the voices.

And possibly always will do.

Yet these extreme effects
are rare.

In the end, it's my impression
that the most significant damage
caused by cannabis is subtle.

It's not at the extremes,

it's the thousands of regular
smokers whose lives are held back.

It's the apathy.

It's the sitting around,
smoking, not getting things done.

The valuable, precious
opportunities of life are lost.

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