CANNABIS AND THE RISKS: FACTS YOU NEED TO KNOW

I used to have fairly liberal views on cannabis and have compared it
favourably in the past with alcohol and tobacco, both of which exact
a bigger toll on our society than all illegal drugs combined. But,
along with most doctors, I have become increasingly concerned in
recent years that the drug is much more dangerous than we thought,
and certainly nowhere near as safe as most teenagers still think. The
days are gone when sensible people argue that cannabis is harmless.
The evidence that has been collected over the past decade shows that
it is clearly not, although for most of the 3-4 million people in the
UK who dabble the risks are still small. The vast majority are
occasional users who, with time, will eventually turn their backs on
the drug and emerge unscathed. This is in stark contrast to the
outlook for the tens of millions who use cigarettes and alcohol - two
legal drugs that kill, maim and injure more people in a weekend than
cannabis does in a year. But there are two groups who seem
particularly vulnerable to the harmful effects of cannabis: heavy
users and those who used the drug at an early age.

Like all parents I like to think that my teenage daughters are
sensible enough to avoid drugs, but I am realistic enough to know
that if they haven't tried cannabis already then there is a good
chance that they will. Statistics show that young children are almost
as likely to experiment with cannabis as with tobacco. According to a
recent survey by the Schools Health Education Unit, one 12-year-old
in 16 and one 15-year-old in four now admits to having tried cannabis
at least once, up from one in 100 and one in 50 respectively in 1987.

The Government has responded to growing concerns among doctors by
performing a U-turn on previous policy and last month upgraded
cannabis from Class C to Class B under the Misuse of Drugs Act, a
message that it hopes will not go unheeded by young people.

I have never been convinced that the legal status of cannabis makes
any real difference to whether a teenager tries it. It has more to do
with peer attitudes, and the overriding belief among teenagers today
is that cannabis is a bit of harmless fun - the most dangerous thing
about a joint being the tobacco that the grass or resin is mixed
with. They are mistaken.

Here are a few key facts that all teenagers (and their parents)
should be made aware of:

Cannabis damages the lungs: Most people consider cannabis to be much
safer than tobacco but, drag for drag, it is actually more harmful.
Cannabis smoke is far more acrid than tobacco and causes more damage
to the lining of the airways. The British Lung Foundation estimates
that smoking an admittedly hefty three to four joints a day causes
the same level of damage as smoking 20 cigarettes a day. And, like
tobacco, it is packed with carcinogens.

Chest physicians are reporting that a growing number of cannabis
users appear to be developing the sort of lung damage normally seen
only in middle-aged and elderly smokers - and up to 20 years earlier.
And it doesn't seem to make much difference how you smoke it.
Research into the relative "safety" of the various smoking devices -
joints, bongs, vaporisers and water pipes - found no significant
difference in the harmful chemicals inhaled. Because water pipes
filter out some of the ingredient (THC) that makes users high, they
tend to inhale more of the harmful components to get a decent hit.

Cannabis can cause irreversible changes in the brain: The most
alarming discovery in recent years has been that cannabis can trigger
serious mental illness such as schizophrenia. As a rough rule of
thumb the average person's lifetime risk of developing schizophrenia
is about one in 100. This risk increases to about one in 30 in
occasional cannabis users and closer to one in 15 in regular users
(at least once a day).

The brains of teenagers appear to be particularly susceptible to the
drug. A recent study in New Zealand found that children who started
to use cannabis before the age of 15 were nearly five times more
likely to develop serious mental illness by their late twenties,
compared with those who started at 18. Neuroscientists suspect that
the greater susceptibility of young teenagers is because the brain
continues to develop during the teen years. Drug use is thought to
influence this final phase of brain formation, increasing the risk of
the type of functional and chemical imbalances associated with
conditions such as schizophrenia.

The problem is compounded because most of the cannabis sold in
Britain today is much more potent than that of a decade ago. These
stronger variants (skunk) contain far more of THC, the active
ingredient, which is| thought to induce psychosis, and far less of
another ingredient (cannabidiol) found in standard varieties, which
is anti-psychotic and protects the brain. But neurochemcal changes
don't alter behaviour alone. Tests on mice suggest that they can also
permanently disrupt a developing brain's ability to remember things,
even after the drug is withdrawn. It is difficult to draw comparisons
with human development, but scientists in the field believe that
exposure before the age of 15 could cause lasting memory deficit.

Cannabis can be addictive: Contrary to street lore that you cannot
become addicted to cannabis, one user in ten develops some form of
dependence, with abstinence leading to craving and withdrawal
effects. Cannabis abuse now accounts for 10 per cent of attendances
at UK drug treatment centres.

Is it a gateway to more dangerous drugs? This is a controversial
area. There is little doubt that cannabis users are more likely to
try harder drugs such as cocaine and heroin, but this gateway effect
is much smaller than we used to think. While most hard drug users
start off trying cannabis, most cannabis users don't end up on hard
drugs. Only one cannabis user in 25 admits to having tried heroin.
That said, the social factors of mixing with peers who are using
drugs and having access to supply can only make progression more
likely. Age is again a factor - younger cannabis smokers are more
likely to move on to hard drugs.

Cannabis and your bones: Recent work indicates that cannabis may
accelerate the thinning of the skeleton that occurs as we age. Bone
is a living tissue that is constantly being remodelled; cells called
osteoblasts lay down bone while osteoclasts dissolve it. Careful
balancing of the activities of both groups of cells mean that overall
bone mass remains steady - at least until the age of 40 - despite our
entire skeleton being replaced every seven years.

Researchers from Aberdeen University have discovered that chemicals
found in cannabis may upset this delicate balance in favour of the
osteoclasts and bone resorption, leading to osteoporosis - a
condition now thought to affect one woman in three, and one man in
ten, over the age of 50.

Cannabis and sex: Little is known about the impact of cannabis on
sexual function but there is growing anecdotal evidence that it may
be linked to shrinking of the testicles and low sex drive in men.
Research published this week suggests that it may increase the odds
of developing testicular cancer. More research is needed but should
any of these links be proved they could become the most powerful
deterrent of all for boys and men.

Nothing in life is totally risk-free and all these potential hazards
need to be put in context - the vast majority of people who try
cannabis will come through the experience unscathed. But for some,
particularly those who use it regularly, it will leave a permanent
scar that could cost them their friends, family, career and possibly
even their lives. At the moment we have no reliable way of
identifying those most at risk but we do know that the earlier you
start the more dangerous the drug is likely to be.