MORE DANGEROUS THAN HEROIN

A Leading Mental Health Expert Now Believes Cannabis Can Cause
Schizophrenia, Fuelling Debate About Legalisation

IF YOU ENJOY smoking marijuana and live in South London, you might like to
start reading the classified section of your local paper more closely.
Sometime early next year, ads will appear inviting people like you to take
free cannabis so that researchers can see precisely what it does to your
brain. The study, thought to be the first of its kind on human beings in
Britain, is being conducted by researchers from the South London and
Maudsley Mental Health Trust and the Institute of Psychiatry.

They know that some may find it controversial to experiment on people with
what is still an illegal drug. But the study's results could prove even
more contentious, because they may eventually help to answer one of the
most highly charged questions about cannabis: can it really make people go mad?

Many parents who have watched their teenagers develop schizophrenia after
starting to use cannabis have blamed the drug for the illness. But until
recently, most doctors believed that, while there was an association
between cannabis use and mental illness, there was no evidence that the
drug actually causes psychosis.

Three new studies published in last month's British Medical Journal have
started to push expert opinion in favour of a causal link. And one of the
supervisors of the South London study, Professor Robin Murray, is about to
push that opinion even further.

Murray, head of psychiatry at the Institute of Psychiatry, is one of the
most prominent mental health specialists in Britain. And he has just
revealed that he has changed his mind about the link between marijuana and
mental illness.

He says that he used to be sceptical when people close to psychotic
patients blamed cannabis for causing the illness. "Relatives would say 'it
seems to be the cannabis that makes my son -- or daughter, or brother --
psychotic'. And I would say, 'Oh, they're being hysterical, they're just
trying to look for something to blame'. Gradually, over the years, we have
come to realise that it does have a significant effect, but it has taken us
a long time to wake up to this."

Murray now believes that cannabis -- the drug we grew up associating with
peace, love and harmlessness -- may be more dangerous than heroin for a
minority of people with a vulnerability to mental illness.

"Because I'm interested in people with schizophrenia, I don't get so
alarmed if people are taking heroin or morphine, because that does not
provoke psychosis," he tells a provocative Channel 4 documentary, Cannabis
Psychosis, to be shown on Monday.

According to Murray, mental health services in London that could cope ten
years ago are today "overflowing" with unexpected patient numbers. "More
people are going psychotic than we expected," he says, "and cannabis is one
of the contributing factors."

His comments come at an awkward time, in view of the Government's decision
to reclassify cannabis as a less dangerous class C drug. Could it be that,
in its eagerness to ease marijuana laws, the Government has overlooked the
downside? And are our mental health services being clogged with patients
suffering from entirely preventable illnesses induced by cannabis use?

Probably not, says Professor Colin Blakemore, Professor of Physiology at
Oxford University, in response to the second question. He and his
colleague, Professor Leslie Iversen, who wrote The Science of Marijuana,
have long argued that cannabis is not as harmful as some have suggested.

When Baroness Greenfield, a pharmacology professor, wrote on these pages
last year that experiments had shown that the drug could shrink or even
kill brain cells, professors Blakemore and Iversen responded with a joint
article accusing her of "an idiosyncratic reading of the scientific and
medical evidence".

They said that the link between cannabis and psychosis had been widely
discussed -- and dismissed -- in the British Medical Journal more than a
century ago, and that if cannabis really was causing schizophrenia and
other mental illnesses, why had the incidence of these illnesses not risen
as dramatically as cannabis use over the past 50 years?

Today, despite the shifting opinion of Murray and others, Blakemore still
doubts that there is enough evidence to say that cannabis causes psychosis.
"I have an open mind on the issue, as one should," he says. "It's well
known, at least anecdotally, that a large fraction of young people with
acute psychosis use cannabis. However, I would say that the incidence of
tobacco use is even higher. So there is some association in habit between
cannabis and tobacco use and psychotic episodes, but the question is
whether there is a causal relationship."

He still thinks that, if such a relationship existed, we would be seeing
many more cases of psychosis than we are: "I don't know of any evidence
that the incidence of schizophrenia has changed a jot in the past 100
years, or ever."

But what of the three new studies published in the November British Medical
Journal? They found what the authors said was a clear association between
cannabis and mental illness, particularly among people who had started
smoking the drug at a young age.

One study in New Zealand, with which Murray was involved, found that 10 per
cent of youths who had used cannabis before the age of 15 had developed
symptoms of schizophrenia by 26, compared with 3 per cent of non-users.

The authors claimed that their research showed, for the first time, strong
evidence that cannabis use triggered schizophrenia, as distinct from the
drug being chosen by people predisposed to developing the illness. At the
very least, they argued, this meant that cannabis use should be delayed
until the late teens.

Blakemore believes that much more should be done to discourage drug use
among children, and that the new research has to be taken seriously. "But,"
he says, "it doesn't absolutely establish a causative relationship."

It is possible, he says, that people with schizophrenia have an aberrant
form of receptor in their brains which means that they have a "hunger" for
the active ingredient in cannabis, tetrahydrocannabinol, or THC. But this
does not mean that the drug causes their illness.

Other psychiatrists agree. Dr Trevor Turner, who has spent 15 years as a
consultant psychiatrist at the inner-city Homerton and St Bartholomew's
hospitals, says: "I have never seen a single case of cannabis psychosis.
The notion that cannabis causes the illness is a major philosophical
fallacy. It can't cause it."

He sees a lot of people with schizophrenia who smoke cannabis. "But because
B happens after A, it doesn't mean that A caused B."

Like Blakemore, Turner says that the incidence of mental illness would have
surged in line with cannabis use if there were a causal link, and it hasn't.

Cannabis use has certainly increased, especially among the young. Overall,
it is the third most popular drug in Britain after tobacco and alcohol.
Half of all respondents in a recent British study admitted trying it.

What worries many medical experts is that people are not smoking the same
sort of marijuana they smoked at Glastonbury 30 years ago.

As recently as the early 1990s, there was only between half and three
quarters of a per cent of THC in most cannabis, according to toxicology
experts such as Professor John Henry, of St Mary's hospital. But today,
says Henry, selective breeding has created much more potent forms of the
drug, such as "skunk", which can contain up to 30 per cent of THC.

He thinks that cannabis's benign reputation is in need of an urgent
makeover. "There is a campaign against tobacco, but everyone says
'cannabis, that's different'," he says.

In fact, cannabis today is so strong that even drug-users are starting to
complain, according to Dr Zerrin Atakan, a consultant psychiatrist with the
South London and Maudsley Trust. "They say it makes them feel paranoid,"
she says. Atakan has spent the past 14 years on the psychiatric
intensive-care wards of South London's hospitals, an experience which has
left her in no doubt that, despite what Blakemore, Iverson and Turner have
argued, there is a clear link between cannabis and psychosis.

She has watched patients who have been doing well for more than a year
suffer tragic overnight relapses after just one puff of cannabis. "There
might not be a direct causal link, but certainly there is a link," she says.

Atakan is one of the prime movers behind the cannabis experiment due to
start in South London next year. It has taken her six years to get various
approvals and appropriate drugs for the research (the Home Office is just
one body which had to approve even this preliminary study, let alone future
research that might involve mentally ill patients).

The study hopes to find 30 volunteers -- 15 heavy users and 15 social users
- -- to take tablets (not smoke joints), then to carry out a series of memory
and motor tasks while undergoing sophisticated brain scans: this way
researchers can see exactly how the drug affects the volunteers' mental
activity.

Meanwhile, it seems likely that controversy will prevail among the experts
- -- leaving those at the front line of the battle against mental illness
confused and worried.

One family appearing in the Channel 4 documentary is that of Gervaise
Hallen, 41, a housing officer, Lee Wright, 31, a mosaic artist, and
Gervaise's teenage son, Cadel Hallen-Brown. Like many women of her
generation, Gervaise smoked marijuana in her youth, and never experienced
any ill-effects. When Cadel reached his teens, she felt it better to let
him smoke at home rather than out of sight with strangers.

And he did smoke, heavily. Eventually he started showing signs of paranoia
and even violence (Lee reports that Cadel "almost attacked me"), at which
point Gervaise and Lee decided that his drug use was becoming harmful.
Cadel said he did not think the drug was a problem, but for his mother, the
effect it had was a shock. "I guess it was kind of a reality hit," she
says. "My son could become a psychotic."

Since the documentary was made, Cadel has turned 18 and left home -- in
part, says Lee, because he and Gervaise were pressuring him about his drug
use. Lee assumes that Cadel is still smoking cannabis.

"It's a fine line between using a drug and abusing a drug," says Lee, "and
that has to be recognised, primarily by parents."

Stories like these are familiar to Marjorie Wallace, the founder and chief
executive of the mental health organisation SANE (Schizophrenia, A National
Emergency). She has spent 16 years meeting family members who have lost a
child, usually a son, to schizophrenia and other mental illnesses.

"I can think of maybe two exceptions out of several hundred people where
there has not been cannabis involved, either in the initial breakdown or
most certainly in any relapse."

She knows that, as yet, there is no conclusive evidence that cannabis
causes schizophrenia: "But anecdotally, I find the evidence startling."

So should we be relaxing cannabis laws? Interestingly, even those most
concerned about the potentially harmful effects of the drug do not advocate
continued prohibition.

"I'm not against it being decriminalised," says Atakan, who argues that it
has uses in other medical disorders and that, if it was legal, its potency
could more readily be regulated.

As for Murray, he has no strong views on the legalisation issue. Cannabis
use is higher in South London, where it is illegal, than in Holland, where
it is not, he says. "So it doesn't seem to me to make much difference. But
society has to balance the enjoyment that many people get from this
substance against the cost to a few."

That balance, so far, is a long way away from being found.

Cannabis Psychosis, directed by Clio David, Channel 4, Monday, December 16,
11.05pm