It's the world's favourite illegal drug.
I'm high on pot.
Ganj, Buddha.
Sticky Icky.
Hemp, marijuana...
In the UK alone,
half of all 16 to 29-year-olds have tried it least once.
Now, for the first time ever, follow an entire trip from start to finish inside your body.
A unique journey that will track cannabis as it hijacks the inner workings of our brain.
It kind of goes pffff!
See how it creates its heart-racing and mind-warping effects.
I don't know if I should have eaten that whole cookie.
Police!
Alongside this drug trip, we'll confront head-on
the biggest myths and controversies that surround this humble weed,
by gaining exclusive access to cutting-edge scientific research...
I'd like you to breathe in...
..to discover, is Cannabis addictive?
Does it destroy our memory?
Who's the Prime Minister?
Er, Gordon Brown.
Oh, no, God! No, David Cameron.
And can it even lead to psychosis?
Have you been receiving any special messages?
I feel like I've got some sort of communication going on,
like a conversation with my boyfriend.
Do you want to stop? Are you all right?
Discover once and for all if this is a harmless herbal high, or the ultimate bad trip.
In the last month, around a million and a half people in the UK have rolled a spliff, smoked a pipe,
sparked up a bong, or eaten a space cake.
They've used Thai stick or resin,
skunk or chronic.
Despite the fact that possession of any type of cannabis
now carries a maximum penalty of five years in prison.
26-year-old Imogen has just returned home from her new job
in the admin department of a large consultancy firm in the City.
OK. Today I'm moving house, so I couldn't be more stressed.
I am fairly broke,
I don't drive, I don't have a boyfriend,
my family live in Cornwall, so I've got no help,
I've got no-one to be there for my big stresses and give me a cuddle.
It's all been really, really last minute.
I'm panicking and stressing and wandering the house, going, "Huh?"
So I'm just going to sit down and say, "Sod it" for 20 minutes
and have a smoke.
After a long day at the office, Imogen likes to unwind in the evenings with a spliff or two.
My little box of wonder.
I don't really feel like I'm hurting anyone or doing anything awful.
I made the decision that it was something that I enjoy
and something that doesn't impact on my life and I can make a genuine risk assessment of that.
There's always this moment when you've had a stressful day, you've come home and rolled
your first spliff and you're really looking forward to it and you can't find your lighter!
Ah, thank God.
Mike is a straight A student waiting for his A-level results.
He's hoping to study history at university.
Mum found my pipe and I think she was a bit worried about what it was.
She assumed it was a crack pipe or something.
I was like, don't worry, it's nothing sinister.
I smoke it because I like to smoke it.
It's not because I need to, it's like, why not?
It makes things more fun, it makes things better.
Unlike Imogen, who smokes every day,
Mike and his friends only like to get high a couple of times a week as a bit of fun.
The two years I've been smoking weed have coincided with my best academic years.
I'm not saying it caused it, but it's obviously not had a bad effect on me.
Mike and Imogen and around three million other people in the UK get high regularly.
That's a bit nice.
It's not very well rolled.
But why is this drug so appealing to so many different people?
And how does it actually work?
This is where the journey begins.
The cannabis smoke is inhaled.
Our lungs are where we absorb oxygen from the air, but they also absorb
other chemicals, like those in smoke from the joint when inhaled.
Many smokers, like Mike and his friends, believe that
holding the smoke in their lungs for up to 15 seconds gives them a stronger high.
They're wrong. It has no effect on the intensity of the high.
But it does jack up the amount of tar they inhale, to four times that of a cigarette.
The tar attacks the small, hair-like cilia that protect the lungs and paralyses them.
This allows the tar to penetrate, leading to a greater risk of chronic bronchitis.
Once inhaled, the cannabis chemicals slip easily
through the membranes lining the lungs and into the bloodstream.
The blood carries them from the lungs to the heart.
Almost immediately, the blood vessels relax and dilate,
allowing the blood to rush around the body.
The body starts to feel warm as excess blood flows to the skin.
It surges to the tiny blood vessels in the eyes, which turn red.
Cool.
What was it I said to that guy in KFC yesterday?
You said you'd like the five piss chicken!
I'm really warm. Is anyone else really warm? It's nice and warm, yeah.
As the blood spreads around the body, blood pressure starts to drop.
If it drops far enough, it can trigger a fainting reflex, also known as a "whitey".
A whitey is when you've had too much of it
and you throw up and it sends your head really, like... whizzy.
So Imogen's reaction is typical.
I'm going to have to sit down.
There's always that sort of...
..first few drags where you go, "And relax!"
Within seconds of entering Imogen's bloodstream, the most powerful ingredient of cannabis,
Delta-9 Tetrahydrocannabinol, or THC, travels in the blood,
up the spine and into the brain.
You kick over from "I'm getting high, I'm getting high" to "I am high!"
And it feels like your eyes are opening up at the back
and it's like a relief thing, it kind of goes pfffff!
Which is... fantastic!
This high can last for up to two hours and starts almost immediately.
I feel kind of floaty,
as opposed to weighed down by stress.
And, erm...
I feel calm and just happy.
One of the first effects is a buzz.
For Mike, everything around him suddenly seems a lot more vivid.
When, like, the sun comes through there, the trees, this sounds stupid now, but it looks really nice.
Is that all you wanted to say? That's all I wanted to say.
The sun looks really nice through the trees?
It's a few BLEEP trees, man!
All right, sorry!
Both Mike and Imogen think they're just chilling,
but they may be putting themselves in danger.
In the hour after smoking cannabis, your risk of having a heart attack increases fivefold.
The THC in their blood has lowered their blood pressure.
The heart senses this and starts to beat faster and faster,
increasing its speed by up to 50 per cent.
Which makes this a bad idea, especially for anyone with a history of heart trouble.
That's a bit sad, it's almost over.
Cannabis affects the way we think, feel and move in ways unmatched by any other drug.
The cannabis plant has actually been around far longer than humans, over 30 million years longer.
Its first recorded use by people was in China, almost 5,000 years ago.
By the 1960s, this mysterious weed was pretty much everywhere.
But scientists were stumped on the nuts and bolts of how it worked.
So they set out to monitor its effects on very willing subjects.
None of us know very much about this drug in any verifiable way.
So, Bill, it's been about two hours since you got the drug.
How do you feel?
Fantastic!
We found out that the drug makes people happy,
it makes them intoxicated and finally, it makes them sleepy.
Dr William Notcutt has spent the last 17 years studying how cannabis works.
What I think is quite amazing,
that here is a plant that grows wild across half the world
that produces a chemical that somehow gets into the brain,
which is quite well protected in the body against strange chemicals.
Yet, it gets into the brain to produce an effect within the brain and within the body.
It was only in 1988 that scientists made a dramatic discovery -
our bodies are hardwired to react to cannabis.
Our brain tells our body what to do by using our nervous system.
This living communication network stretches from our brain
down to our spine and out through our body.
It allows us to see, hear and feel the world around us and react to it.
When you smoke a joint, cannabis penetrates deep into the brain
and hijacks the nervous system like a herbal terrorist.
The human brain is composed of networks of billions of long nerve cells.
Messages pass from one cell to the next across narrow gaps.
On either side of the gap are tiny gates that control this flow of information.
They're called receptors.
The THC molecule penetrates the brain and seizes control of the receptor.
Once it controls the receptors, it controls how they work.
These receptors show up in especially high numbers
in the areas of the brain that regulate our memory, appetite, thoughts and mood.
So it's here that cannabis works its magic.
It makes you high, this is the expression that's usually used.
It makes them feel very good,
forget their cares and worries and sends them up on top of the clouds.
Cannabis is a big part of 20-year-old Chet and 18-year-old Alex's lives.
I found when I first tried it, all my senses were enhanced,
so taste, touch, smell, everything seemed a lot clearer.
It puts you in this bubble for a few hours where you don't worry about anything.
They like to get high several times a day.
Best experience of getting high? Oh, God!
Just the culture around it, making friends and meeting people.
I met Alex cos we realized we were both stoned in class.
We both just said, "Man, I'm so high!"
And from that day, we just clicked.
And we've been really good friends ever since.
Unlike Alex, Chet still isn't sure if he wants to go university.
Alex is more motivated then me. Yeah, I'm going to uni and everything.
Tonight, they're making weed flapjacks.
Five what? Ounces.
Unlike other drugs like cocaine or speed, cannabis doesn't break down in water, only in oil.
Or in this case, butter.
So if we heat the weed ground up in the butter, then all the stuff
that gets you high in the weed will go into the butter.
THC! And then you get stoned, eventually.
If they're caught, they'll face the same penalty as they would for possession of any form of cannabis.
About six months ago, Chet's passion for weed turned into more of an obsession.
Check the pot in the pot.
It got a bit much. I was homeless, squatting in this little house,
with no heat, just getting stoned all the time.
And it looked like a crack den, it was pretty horrible.
And that was really all I was doing with my time,
just getting people over and getting stoned. And it stopped being fun.
Smells great. It smells really weedy.
Chet now tries to limit the amount he gets high.
Smoking cannabis is supposed to be away from routine and everyday life.
It's supposed to get you away from that.
And if it becomes that, that's when it becomes a problem.
So you've got to keep it fun, really.
Mate! These are looking well good.
The weed flapjacks are ready, and the guys are hoping they'll make a walk in the forest a lot more interesting.
Oh, wow, that looks cool.
I like the forest. Let's eat them, then walk, it takes a little while.
So, what happens to the body when cannabis is eaten, rather than smoked?
You can see green in them.
I like the taste of weed anyway. It's quite nice. It's herby.
The cannabis is swallowed in the lumps of flapjack and travels to the stomach,
where it starts being broken down by the digestive juices.
But digestion is a relatively slow process compared to the instant high of smoking a joint.
It's also riskier.
When you're smoking, it's pretty much instant when you feel the effects,
so you can stop if it's too much, or you can carry on if you want.
But with edibles, it takes a couple of hours to come up.
And then, like, if you eat a couple,
you don't know how hard it's going to hit you once it comes in.
Contrary to popular opinion, eating weed doesn't make it any stronger.
Only about a tenth of the mind-altering THC is absorbed,
versus up to five times that when it's smoked.
But once the high hits, it lasts a lot longer, around six hours.
I don't know if I should have eaten that whole cookie!
After about 45 minutes, their weed flapjacks are almost fully digested.
The THC slips through the walls of their small intestine and enters the bloodstream.
It travels in their blood, up their bodies, to the back of the neck,
where it enters into a part of the brain called the hypothalamus.
This is the control centre for hunger.
THC locks onto the receptors here and starts flooding their bodies
with messages telling them to seek out food,
whether they're hungry or not.
Most people just call this the "munchies", and they're almost impossible to resist.
I really want to eat a muffin so bad!
Yay!
Another risk is if they gorge on more cannabis cakes, they could get higher and higher.
Luckily, these muffins don't have any weed in them.
HE MAKES BEATBOX NOISES
It's 15 minutes later, and the forest has never looked more beautiful to them.
Yeah, they're all sparkling.
Drugs definitely, like, helped me get an interest in nature,
just from being high in the forest
and looking at it, and how cool it is.
It's the simple things that make you smile when you're high.
Like puddles!
But what exactly is it that makes even puddles seem so interesting?
Inhale.
Keep going, keep inhaling, come on.
For years, scientists have been trying to pin down how the world looks to our brain when we're high.
Left hand bend coming up, going into third gear.
This subject is driving quite efficiently and carefully, but he is in fact high.
There's no slack in that at all.
Now some ground-breaking new research is going to help 23-year-old Ravi
get a window into what happens inside his brain when he gets stoned.
A postgraduate student, he only gets high at the weekends.
I used to smoke a lot more at university, generally with friends.
It's just really nice on a sunny day in a park.
It's quite social, I suppose. It's fun. It's just really pleasant, you feel really relaxed.
Today, at University College London, he'll be part of a unique experiment.
It should reveal if this pleasant pastime damages his brain function.
Ravi, I'd like you to breathe in.
Ravi inhales pure THC through a vaporiser, which heats the drug
without allowing it to combust, so it's less harmful to his lungs.
Just as it does when smoked in a joint, the THC travels through his lungs and into his bloodstream.
Within seconds, it hits his brain and gets to work.
How are you feeling? Everybody happy. Yeah. Stoned?
Yeah, feeling something.
First up, a simple memory test.
How old are you? 23. What's the date? 30th of July.
Who's the Prime Minister?
Gordon Brown. Oh, no, God! No, David Cameron.
It's not a good start. Now, Ravi must take a more testing memory test.
He's played a 20-second news story.
'Local police are collaborating with CID...'
Deep inside Ravi's brain is the hippocampus.
This is his memory centre.
Surprisingly, one of its main functions isn't to remember,
but to forget.
We can't remember everything we see and hear.
Every face, every car, every story we're told.
It would clog up our brains.
So this is where the brain decides what's worth keeping as a memory, and what should just be chucked away.
It's also an area of the brain that has a lot of receptors that are vulnerable to a takeover by THC.
Almost immediately, the THC turns up the dial on messages telling Ravi's brain to forget.
So, all new information risks being rejected before it gets a chance to become a memory.
'..large houses in Cheshire last month.'
Now, Ravi must try and repeat back the story.
Um, thieves were caught on the manor of Lord Dartston.
Um, yesterday. And a, er...
police investigation has been launched.
That's pretty much all I can remember.
The good news is, Ravi probably won't recall how badly he did on this test.
We know when people are intoxicated, their memory is impaired,
but chronically, so longer term, the results have been equivocal.
There seems to be little longer term memory impairment in the majority of cannabis users.
But Ravi's damaged short-term memory could be having an unexpected benefit. G.
He's asked to come up with as many words starting with the same letter as he can.
Gregarious, gracious,
grange, grog, gnome.
And on this test, he seems to be doing very well.
Grip.
Um, gustation.
What we found so far is that verbal fluency goes up, so people can
generate more words when they're stoned compared to when they're not.
And we think cannabis might make it easier
for you to make associations between concepts and words in your brain.
Some people say it helps them with problem-solving or creativity.
It could be that, by halting the flow of new information into our brain, we are less distracted.
So we start making new connections in our mind.
As a tree, I was... I could be a tree...
This could explain why everyone from jazz musicians
to computer programmers have looked to weed for inspiration.
When I'm high, it enhances my creativity.
One was painted before going up on weed, and the other while high on weed.
HE BEATBOXES
Wow! Look how cool that looks.
It looks awesome. It looks like Jurassic Park!
It's been an hour and a half since Chet and Alex ate their flapjacks.
Their impaired memory is about to affect their ability to navigate.
We're going downhill. Yep.
We're definitely going downhill.
How are we getting in there? Um, jump!
Rocket boots. Go across, we can jump there.
We can't jump that!
Does it look jumpable? Yeah.
Actually, I'm not too sure of this.
The hippocampus is where the brain stores information about every move we've ever made.
We call on this database to work out how to achieve all physical tasks,
like jumping a ditch.
But the THC in the cannabis is interfering with the messages to and from the database,
so the brain's no longer sure what the body can and can't do.
What the f... Especially when it's confronted with yet another ditch.
That's not jumpable, actually.
That is jumpable. Perseverance.
The abyss they see before them is actually a shallow ditch that's three feet wide and a couple of feet deep.
That looks like it gets deep really early. It looks pretty dangerous.
Yeah, another obstacle for the stoner video game.
He's shaking, he's shaking!
We've all got to get across here.
The THC also hijacks messages to the part of their brain that controls balance and coordination.
Just jump, Alex, jump.
So, even whey they picture a smooth leap in their mind, the message can't get through to their body.
Put one up and then spring off.
Eventually, the lads cross the ditch,
in one piece. Sick! We did it.
When cannabis distorts the messaging system between our brain
and our limbs, it can turn a straightforward walk in the forest into a complex obstacle course.
It's been a bit of struggle, but Imogen has moved most of her stuff out of her bedroom.
But the effects of the joint that she smoked an hour ago are starting to wear off.
And her thoughts soon turn to having another one.
I'm going to grab a drink and a smoke of J.
Now, I definitely feel like this is a reward. Happy days.
Most users like Imogen think of cannabis as being a relatively safe, natural drug.
But the more cannabis she smokes, the more she needs to smoke to feel its pleasurable effects.
So, the big question is, is it addictive?
The idea of waking up one morning and saying,
"From this day forth, I shall never smoke marijuana again,"
is as stupid as...
giving up chocolate or carbohydrates.
It's like...
..I could do that and maybe I would be healthier or thinner.
But I certainly wouldn't be happier.
And...is it really that big a deal?
But most experts agree that users, especially those who smoke heavily,
can become dependent on cannabis.
25-year-old Chris works full-time in a popular restaurant chain.
I smoke weed all the time, usually I smoke a bong and I'll be smoking
that from the moment I wake up in the morning.
And then I'll come home from work and smoke a bit. I'm always stoned.
It's not good, but that's the way I am.
Chris first got high when he was just eleven.
That's, like, more than half my life.
The thing that gets to me about smoking cannabis is,
what have I got to show for it, really?
I've got a job, I do work, but most of my money goes on to weed. Everything goes on to weed.
This is the room that I tend to smoke cannabis in. I watch telly here.
I lie down and chill out and watch the world go by.
It's just crap, it's no way of living, basically.
Until he quits, his girlfriend won't let him move in with her.
I'd love to be in a better job, in college,
spending more time in a happier relationship with my girlfriend.
It's really hard, actually.
The question is, when does habit turn into dependency?
If you keep using it, when you experience negative consequences,
so you're dropping out of school, your relationships are going downhill.
You get anxious when you don't get the drug. You get massive cravings for it.
Chris's girlfriend Rachel believes he has a problem.
For you, it's not for the buzz, it's just feeling like it's chilling you out. Yeah.
But, to me, it's not chilling you out.
I am dependent on cannabis.
When she's taken me weed off me in an argument and she's held it,
and I've grabbed her hand, she's like, "No, you're not having it."
And I've really thought she was taking it
and throwing it away, so I've really wanted it back.
So I'm really like scuffling with her to try and get it back.
That was a bad time, because I really stood back afterwards
and thought, "You muppet, look at how you've just been."
Cannabis is now the second most common drug of referral to rehab clinics, after heroin.
I love you. I love you. Do you? Yeah.
Chris has decided to quit, but after 14 years of getting high, it's not going to be easy.
He heads back to his flat, for his last smoke ever.
An estimated one in ten smokers will become dependent on cannabis.
It's sad, really, sitting here smoking weed on my own.
Quitting cannabis doesn't lead to dramatic cold turkey effects, like harder drugs.
The withdrawal symptoms are quite hard to specify,
but people generally experience things like not being able to sleep and increased anxiety.
Other symptoms include irritability and decreased appetite -
the exact opposite of the positive effects of cannabis.
Smoking weed is bad.
For Chris, quitting will be particularly difficult, because he is also addicted to cigarettes.
This is last my last bong.
His withdrawal symptoms should begin within about one day,
peak at two to three days and subside within one to two weeks.
No more weed now.
His girlfriend will record his experience on a camcorder.
What time is it? 12.51am.
By the next morning, Chris is already starting to struggle.
Don't take the piss out of me. You're taking the piss?
Don't take the mick. I'm not.
I'm really being serious, don't take the mick.
What was you just saying, what do you want to do?
By evening, he's back at his flat getting high.
He was feeling it thought, weren't you? Yeah, I did try to stop smoking weed.
Twice I stopped smoking weed, but found it really hard.
I did do my best. I didn't smoke weed all the next day, after I took my last mix.
And then, come to night-time, I was really feeling it.
I was just stressing and kicking off and I ended up going and having a smoke.
They just think people can get off it easily -
and I suppose you can, but it's not that simple.
Chris is not alone.
The rates of addiction to cannabis are rising steadily.
Experts believe this could be down to one thing - the arrival of super-strong skunk.
Police seizures show that skunk accounted for barely 10% of the cannabis sold here in the late 1990s.
Last year, it was 80%.
But can a plant really be to blame for reactions like these?
Your hear voices and they sometimes control you to do something.
The reason that I'm saying three to these statements is because,
they go into my head and it happens.
Are we sitting on a mental health time bomb?
..increased risk of depression and schizophrenia...
Skunk, why is it so strong and potentially dangerous?
Skunk is the name given to genetically-engineered weed,
designed to deliver the maximum dose of mind-altering THC.
I don't like the word "skunk", because I think it's just a bit like a fear-mongering sort of word.
Grown under hot lights in enclosed spaces, the female plants are kept
in a perpetual state of sexual frustration.
They overproduce THC, to attract pollen from male plants that don't exist.
The best skunk you get will smell ever so slightly
like an alleyway that cats have been doing their business in.
In this hothouse environment, levels of THC can soar to five times that of ordinary cannabis.
The first time I remember smoking it, ten seconds later, I just
fell backwards on to the bed and just lay there for about 15 minutes.
But Chet and Alex, and Imogen and Mike, all continue to smoke skunk.
So how strong is the evidence that skunk leads to mental illness?
In South London, psychiatrist, Dr Robin Murray, has been studying the subject
for the last eight years - and he's convinced there is a link.
'The people that we see'
have usually been smoking cannabis for at least five years.
They're smoking every day and they are particularly likely to be smoking skunk.
In his patients, this combination appears to lead to a condition known as psychosis.
Psychosis is the ultimate bad trip, an altered mental state that can
include hallucinations and severe paranoia.
So, anybody who has a hallucination or a delusion,
we would regard as psychotic.
Sometimes these illnesses last for a few days, or a week or two.
But if they last for months or years, we term them "schizophrenia".
31-year-old David can still remember his first joint clearly.
'My friends called me over, when I was'
over the field and they said,
"Come on, Dave, we're having a smoke."
And I said, "Yeah OK." I thought, I've never tried this before.
I had, about, a joint.
After that, I just couldn't stand up.
I had a massive head rush, I thought, "I'm not going to do that again."
But when you say to yourself you're not going to do cannabis again, you do it again.
His father died when he was seven and his mother Jo brought up him and his sister.
Yes, Dave, I'm fine. How are you? Yeah, I'm all right. Did you get the bus over? Yes, I did.
He started getting high when he was 13 and he was soon smoking weed regularly.
Before long, he started having strange experiences.
I was walking home and I heard noises from the bus,
like, the whole.. people on the bus were, like,
spitting and it sounded like raindrops.
Jo had no idea her son was getting high until, after just three months of smoking,
his paranoia spiralled out of control.
Do you remember this one?
Yeah, I do.
'David was bit agitated.'
We were standing in the kitchen and he had a small hammer in his hand
and he said to me, "You're NOT my mum."
You hear voices and they sometimes control you to do something,
that you have no control over.
Yeah, that was when I was in hospital.
David was diagnosed as a paranoid schizophrenic and remained in a psychiatric unit for ten years.
This is the other one, David. You look very thoughtful there.
The big question is, how much is cannabis to blame for David's condition?
That question is rather like saying,
could smoking cigarettes, on its own, cause a heart attack?
Many disorders result from a combination of risk factors.
For schizophrenia, having a family history, some difficulties in childhood -
a parent dying, for example - these all add up. And cannabis is one of these risk factors.
It's only now that Jo can see how her husband's early death affected her son in more ways than one.
I didn't know that David's father
had a mental illness until David's father killed himself.
I didn't mean to take it.
When I think about it, I wish I'd never tried it in the first place.
But the precise nature of the link between skunk and psychosis still remains unclear.
Chet and Alex and their friends ate their weed flapjacks two hours ago
and things have taken a turn for the worse.
Urgh.
Following the initial euphoria, users can start to feel anxious or distrustful.
I just heard someone shout. Yeah, the same.
So how does a normal high turn into paranoia?
Scientists suspect it could be down to a chemical in our brain
that makes us focus our attention on our surroundings.
I'm pretty sure I've got an ant crawling up me. Eugh!
THC appears to rev up production of this chemical and this switches our brain onto high alert.
What was that? Was that a train?
I think it was a bear. A bear?
This can make things seem more meaningful than they are.
'Because of the increased level of this brain chemical,'
someone's face might suddenly seem really important
and stand out at you. And then, you come up with
an explanation for why that this is.
And that might be, "That person is watching me, this person is looking at me."
Gradually, this develops into a kind of paranoia.
"This person hates me."
There's just bugs everywhere. There are horrible massive ants, look at them.
Whoa. What? Do you reckon there's adders in the grass?
In extreme cases, people start seeing and hearing things that aren't there.
There's loads of jumping spiders everywhere.
In fact, an estimated one in ten cannabis users will experience bouts
of hallucinations, anxiety and paranoia.
Scientists suspect a vulnerability to psychosis could be, in part, genetic.
'It would be great if we could go to a music festival'
and have a little tent at the entrance and do a little stab on everybody's thumb as they came in.
And, an hour later, be able to tell them,
"You have the genes which make you vulnerable to going psychotic
"after taking cannabis and therefore you should avoid it at all costs."
And then the other 90% of the population, say, "You're OK,
"don't worry about it, you can smoke cannabis for the weekend."
We're not at that stage yet.
So, for a small percentage of the population, getting high is something of a lottery.
For very young smokers, it's more like Russian roulette.
People who start smoking before 15 seem to have a much greater risk
of developing the harmful effects from smoking the drug - things like psychosis and memory impairment.
It could be the brain is still developing in adolescence.
And maybe, if you throw a lot of cannabis at your brain when your
neural systems are still developing, it may cause some wiring changes from which you may not recover.
So, cannabis is a bad idea for anyone under the age of 15, or with a vulnerability to psychosis.
But it now appears even people with no history of mental illness can have a bad trip with skunk,
like this student who, to protect her future job prospects, wants to be known as Catherine.
With normal weed, if I'm happy and having a good time with the right people, it's great.
But with skunk, if I'm on a low ebb, if I've got not much energy,
I'm likely to sink into a low energy-less, enthusiasm-less pit.
She's 19 and only gets high a couple of times a week - and prefers not to smoke skunk.
Dr Celia Morgan and her team from UCL have so far visited
the homes of 450 smokers, like Catherine.
'There are so many young people that smoke cannabis.'
Whilst it's only a small number that experience these kinds of harms from them,
if we can identify what makes people vulnerable to these harms, then we can protect these people from them.
At UCL, they're approaching the link between cannabis and psychosis from a whole new angle,
by looking, not at the genetic make-up of the person, but at the composition of the plant itself.
The second most active ingredient after THC is cannabidiol, or CBD.
It grows alongside the THC in tiny bubbles of resin, but it's present in only small quantities in skunk.
Growing cannabis under 24-hour lighting seems to increase the THC content and reduce the CBD content.
And research shows that CBD might counter some of THC's ill effects.
So Dr Morgan wants to see if CBD might be powerful enough to reduce the risk of a bad trip.
I might need all of that.
The first step is to take a sample of Catherine's weed, to test later for CBD levels.
How would you describe that type of cannabis? It's Thai weed.
Catherine is then asked to go outside and get high, like she normally she does.
I think probably one of the best experiences is that
myself and one of my best friend will have heart to hearts
and get emotionally close.
And that's just part of the process in smoking a joint - to chill out, unwind, offload.
Now she's ready to start the test.
How are you feeling? Do you feel stoned?
I want to you to say how much these describe your experience right now.
On a scale of nought, not at all, one, slightly, two, moderately, and three, strongly.
Dr Morgan wants to see what's happening to her mood.
She's looking out for any signs of extreme anxiety or paranoia.
Your mood is going up and down a lot? Two.
You feel that you can predict what is about to happen? Two.
You think people are saying or doing things to annoy you? One.
You find it more difficult than usual to start doing things?
Two!
'So, Catherine had some thought disorders, things like not being able to follow conversations,'
having a lot of thoughts at once.
But she didn't show very many perceptual disturbances or paranoia.
The next step is to test what's in her drugs...
..in particular, the amount of mind-altering THC in her cannabis, as compared to the more mellow CBD.
So this is quite interesting.
Catherine's cannabis contained about 7% THC, which is an average level.
But it also contained what we would call a high level of CBD, 0.4%.
So it seems to be offsetting some of the effects of THC.
The next stage is to bring Catherine into the lab, to give her pure THC, with no CBD.
This is the lab equivalent of skunk.
Ten. And breathe out as slowly as you can.
It gets you there. It's quite tickly.
Probably need some water in a mo. I'll go and get you some. Cheers.
Once inside Catherine's blood, the THC travels up to her brain
and, within five minutes, she starts to react.
Are you hearing sounds or having visions that you think others are not able to see? Yeah.
Yeah. What sort of thing?
Um, I feel, like,
um, parallel to this situation.
There's another situation going on, which is a dream.
She's experiencing a disconnection with reality.
Have you been receiving any special messages from people or from the way things are arranged around you?
Yes. What sorts of messages?
I feel like I've got some sort of communication going on,
like a conversation with my boyfriend. Oh, really?
Yeah, parallel to this one.
Some sort of telepathic type communication? Yeah.
And how does that make you feel?
Special. Special, OK.
'So Catherine had, what we would say,'
was an actual psychotic reaction, so she thought she could communicate
telepathically with her boyfriend.
She thought she was simultaneously experiencing two different realities.
Do you think you're being talked about? Three.
You're experiencing something very special or important? Three.
Before long, paranoia creeps in.
Celia, could I just stop you, while I'm having this thought?
The reason I'm saying "three" to these statements is because
when you say them, they go into my head and it happens.
Do you want to stop? Are you all right?
I don't mind go on, but I just think it would be scientifically inaccurate,
because it's like planting a thought there and then I say "yeah".
'What we saw was a classic example of how some people'
are more vulnerable to the effects of THC than others.
But, when she smoked non-skunk weed at home, the CBD in it appeared
to counteract some of these ill effects.
One of our aims is that, if people are going to smoke cannabis, we'd strongly advise them to smoke
strains like hash and normal weed, rather than things like skunk, with a much higher THC content.
So, here in the UK, cannabis comes with serious health warnings
and a possible prison sentence of up to five years for possession.
But, in some parts of the United States, it's a whole different story.
Marijuana is being touted as a wonder drug -
a potential cure-all for any number of conditions.
RADIO: Hello, I'm Dr Greenthumb. Have you ever had the problem
of running out of weed and just can't find some anywhere?
Right this way, to see the Cush Doctor today.
Welcome to California... The doctor is in.
..one of 15 states where "medical" marijuana is now legal.
I use medical marijuana for anxiety, neck pain and back pain.
I have a torn ligament in my knee.
Doctors routinely prescribe it for depression, to stimulate the appetite of AIDS patients,
to help people sleep - and even for writer's block.
TV: Medical marijuana stores have been sprouting like weeds in LA.
Here in Los Angeles, there are currently more cannabis dispensaries than there are Starbucks.
Cookies, two or three different kinds of cookies. Pies.
Chocolate milk, also.
No surprise that cannabis is now the number one cash crop in America.
He-he-he! Check it out, man.
But critics say it is too easy to get.
The compassionate use is sort of being abused by people that would seek out recreational use.
RADIO: Thanks, Dr Green. # Doctor. #
Back in the UK, there's no sign of any cannabis dispensaries on the high street.
That's because the law makes no distinction between supplying cannabis
for recreational reasons, versus medical ones. Both carry a maximum prison sentence of 14 years.
18-year-old Hannah works in a nursing home.
Her mum Teresa is one of the 100,000 people in the UK who suffers from multiple sclerosis.
'She got her first bout of her MS years and years ago,
'but they didn't realise it was MS at the time.'
It took about two years for her to finally
get diagnosed with it, when I was about eleven.
The MS is causing Teresa's body to attack her own nervous system.
Too many messages are being fired from her brain to her legs,
which causes her leg muscles to seize up in painful cramps.
It's like someone's got a tourniquet round your leg and then, as you walk,
that tourniquet starts to cramp down, until such time
as you don't know how to pick one foot off the floor to keep walking.
About 30% of MS sufferers report that smoking cannabis helps with their symptoms.
But Teresa is a mum.
She's never broken a law in her life.
My mum gave me the normal parent drug speech, probably when I went to high school, so about ten years old.
But it was the normal "Be sensible, it can ruin your life", etc, etc.
That's very kind.
You've got a smile, that's what you've got.
'I've never taken any kind of recreational drugs.'
I don't really understand what "high" is, but my head is always,
it's not up there in the clouds, it's kind of down here with me.
Now she's about to take a hit of cannabis
in the middle of a Norfolk high street.
This is Britain's answer to medical marijuana.
It's a spray called Sativex, that's now legal.
She sprays the drug into her mouth.
It's specially designed to get absorbed into her bloodstream through her throat.
The drug travels straight to her brain, where it starts slowing down the messages being fired at her legs.
Her leg muscles begin to relax.
For the last four years, Hannah has brought her mum to see Dr William Notcutt,
who has been conducting one of the few legal marijuana trials in the UK.
OK, thanks very much.
'Teresa is a typical example of the benefits of cannabis to a patient.'
This isn't a wonder drug. It's not a miracle cure for MS,
or for control of the symptoms.
But many patients do not get benefit from the existing drugs,
so this gives us another very useful, safe drug,
which has a potential for helping a lot of patients.
So, off you go. Let's see how you can walk.
Cannabis is a unique plant that has the power to change our consciousness.
To some, it's a valuable medicine that has been overlooked for too long.
For others, it's a harmless pastime.
Mike had no problem quitting while he was revising.
He needs three As in order to go to his university of choice.
I got two A stars and an A, so I'm very pleased with myself today.
I think it's definitely against the stereotype that people who smoke weed are like dropouts.
But not everyone can share Mike's casual approach to cannabis.
I'm at a bit of a crossroads. I'm having a bit of a mid-youth crisis.
I'd like to go to uni and study pharmacology or something like that,
but I know that I'm not good enough at science to be able to do that,
so I want to do something a bit different, I don't know what.
Books and socks. Perfect combination.
It definitely makes me less organised,
but then you've got to balance it out.
Like the state I was in earlier,
would I have brought it all in here and done it properly, or would I have just panicked and done bits
and then had a nervous breakdown and cried?
Oh.
But, whereas Imogen finds cannabis a fun antidote to stress... That feels good.
..for some, the high eventually turns to a low.
'Good afternoon, Lifeline!'
Yeah, hi, I'm wondering if you can help me.
I smoke cannabis and stuff like that and I really want to get off cannabis now.
Chris has decided he needs help, if he's going to move on with his life.
Thanks. Bye.
But, in the end, for even the most committed stoner,
the ultimate chill-out drug might prove too effective for its own good.
If everyone in the world smoked weed,
the world would be an awesome place, it would be a lot more chilled out.
People wouldn't start wars. But maybe no-one would get anything done? Yeah.
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