SO HOW DANGEROUS IS SKUNK?

Our Decision to Drop the Independent on Sunday's 1997 Decriminalise
Cannabis Campaign Has Been Applauded and Decried Throughout the
World. at the Heart of the Controversy Is the Link Between Skunk and
Schizophrenia

The UN called the move courageous. Mental health experts described it
as a crucial intervention. Sir Richard Branson says it is time to
think again. And on pro-marijuana blogs and chatrooms from Sydney to
Sarajevo, the mood was more murderous than mellow.

Seven days after The Independent on Sunday published evidence that
almost 10,000 under-18s needed drug rehabilitation for cannabis use
in Britain last year, a ferocious debate has begun over whether a
potent new form of the drug is leading to growing mental health problems.

Beneath the headline: Cannabis - An Apology, the IoS revealed last
week that more than 22,000 people were treated last year by the NHS
for addiction and psychological problems caused by smoking skunk,
which is up to 10 times stronger than resin or grass.

Ten years after Rosie Boycott, this newspaper's then editor, launched
a campaign to have marijuana legalised, the IoS last week reversed
its stance, stating that the evidence of mental health problems among
smokers made the current 'C' classification correct.

The move has provoked an international debate about the threat posed
by cannabis in general and skunk in particular. The warnings about
the effects on mental health were underlined yesterday in a new
report, saying almost a quarter of all new cases of schizophrenia
would stem from cannabis smoking by 2010.

The study, published in the journal Addiction, also predicts that
young men who smoke cannabis will be particularly at risk. The use of
cannabis among under-18s rose 18-fold in the 30 years to 2002,
according to the researchers.

Dr John MacLeod, co-author of the study, said: "If you assume a link
[with cannabis] then the number of cases of schizophrenia will
increase in line with increased use of the drug." Antonio Maria
Costa, the executive director of the United Nations office on drugs
and crime, yesterday called for people to wake up to the fact that
cannabis is now a dangerous drug wrongly portrayed as a "gentle,
harmless substance".

Writing in today's IoS, Mr Costa says that is no longer the case as a
result of the potency of skunk, adding: "The cannabis now in
circulation is many times more powerful than the weed which today's
ageing baby-boomers smoked in college. Evidence of the damage to
mental health caused by cannabis use - from loss of concentration to
paranoia, aggressiveness and outright psychosis - is mounting and
cannot be ignored."

Sir Richard Branson, head of the Virgin Group, who was a supporter of
the IoS decriminalisation campaign, said yesterday: "The arrival of
genetically engineered skunk has merited a new look at the situation."

Medical experts are now warning that the addictive nature of the drug
means that detox clinics are needed. A report published in The Lancet
last week showed how cannabis is more harmful than drugs such as LSD
and ecstasy - but less so than alcohol and tobacco.

The number of people needing emergency treatment due to cannabis has
virtually doubled in five years - from 581 in 2001 to near 1,000 last year.

But not everybody has welcomed the debate. Pro-legalisation
campaigners claim the evidence for cannabis's damaging effects shows
an association between the drug and psychosis, but not that one is
the cause of the other. A more likely explanation, they argue, is
that people in the early stages of mental illness may use the drug as
a form of self-medication.

Roland Hyams a music PR and a supporter of decriminalisation, said:
"I think alcohol is far more to blame for mental illness than
cannabis. I've smoked plenty of skunk and never had problems."

However, some doctors now believe cannabis users have to take
increasing quantities to experience the same "hit". A third of users
are said to experience physical or mental withdrawal symptoms. One
user in 10 is at risk of becoming an addict. "The strength of skunk
means that users are more likely to become addicted to cannabis now,"
said Professor Peter Jones, professor of psychiatry at the University
of Cambridge. "Withdrawal symptoms include anxiety, sleep disturbance
and tremors."

J-Rock, from the rap group Big Brovaz and a former skunk addict, gave
up the drug a year ago. He said: "Cannabis and skunk are definitely
addictive and lead to psychological and physical changes in any person."

The 28-year-old musician started using when he was 13. When he came
off the drug, he experienced headaches and mood swings. He describes
the detox process as one of getting his sanity back. He says that
skunk-induced paranoia is behind the surge in violent crime: "If
you're on skunk and you have a confrontation with somebody, you feel
almost untouchable."

Is this the evidence that shows cannabis is bad for your brain?

The controversial findings, published in the 'Journal of Psychoactive
Drugs', give an indication of the possible effects of cannabis.

Images of the brain were created by single-photon-emission
computerised tomography, which works by looking at blood supply and
brain activity. Patients are injected with a radioactive substance
which goes into the bloodstream and shows up on a brain scan.
'Mottled' areas represent areas where brain function is weakened .
But some doctors question the validity of the images.

Normal Brain

The brain image has a relatively smooth, uniform surface, with little
indication of a loss of any brain function. It is the brain of
someone who does not use cannabis and is an example of what an
average brain can look like.

The 16-Year-Old Who Smokes Every Day

This scan, which shows a marked difference from the normal brain, is
of a teenager who began using cannabis daily at 14 years of age. The
image suggests that after just two years of using the drug, the brain
is already affected

The 18-Year-Old Who Smoked for Two Years

The brain of a teenager who started using cannabis when 16 is badly
pitted and scarred. The subject took the drug several times a week.
Like the previous scan, this also apparently shows damage after two
years of cannabis use.

The 28-Year-Old Who Smoked for 10 Years

This scan shows how long-term damage can be caused by cannabis use.
The subject had smoked skunk for 10 years. As with the other images
shown, it appears to show decreased activity in the pre-frontal
cortex and temporal-lobe areas.