THE BUTTERFLY AND THE DRUG ADDICT

The general debate about drug abuse ignores the scientific facts. Roger
Highfield explores a jungle of myths.

To understand why addiction has spread to the point where 150,000 people
inject drugs in Britain today, we should adopt the same approach as an
ecologist studying the emergence of a new species of butterfly in the
Amazon rainforest.

Vary the characteristics of users, the supply or type of drugs, indeed any
feature of the environment, and the nation's population of drug users could
soar or plummet, just as the fortunes of the insect change in response to
the complex ecology of the forest, according to Prof Griffith Edwards, the
former head of the National Addiction Centre.

In the past week, media reports have extolled the health benefits of
cannabis, in treating brain cancer and multiple sclerosis, while the
American Heart Association warned that, in the first hour after smoking
marijuana, a person's risk of a heart attack soars five-fold.

For Prof Edwards, this drip drip drip of drug stories obscures the complex
ecology of abuse. Later this month, as part of the Last Word Lecture
series, he will highlight the shortcomings of the "science free debate"
about drugs by describing addicts "as a species who inhabit an eco-system -
a metaphorical forest as it were".

To understand the wax and wane of drug addiction requires every kind of
science, social and laboratory. "That's what is so challenging about the
drug problem and that is what the peddlers of simplistic insights and the
pushers of extreme remedies so easily forget."

When he refers to drugs, he means both licit and illicit: while there were
around 2,250 deaths in England and Wales as a result of drug overdoses in
1998, smoking kills about 110,000 people each year and alcohol perhaps 40,000.

The discussion of the impact of alcohol and cigarettes has been largely
neglected compared with illicit drugs. None the less, the rising impact of
the latter is striking. In 1960, there were 437 addicts known to the Home
Office. Four decades later, addiction has multiplied some 340-fold.

Just as the beetle may flourish in the detritus under a forest canopy, so
drug abuse thrives in conditions of poverty. Overdose deaths among 15 to
44-year-olds are about seven times higher in the most deprived, as opposed
to the least deprived areas, in England and Wales.

An earlier study underlined how a favourite media story - the tragic drugs
death of a bright young thing - sends out the wrong signal about which
section of society is at risk: dependence increases with deprivation, with
the most deprived almost 10 times as vulnerable as the least.

Drugs, cigarettes and alcohol provide a reprieve from hardship, however
temporary, so that the anomie and alienation which go with deprivation are
contributory factors to an "environmental climate for drug misuse."

"Cigarettes are moving toward becoming a poverty drug," said Prof Edwards.
"Alcohol use certainly crosses the class spectrum, but there is recent
evidence to suggest a clustering of heavy drinkers among the poor."

Neuropharmacology reveals that mood changes often result from the effects
of drugs on the messenger chemical dopamine within the brain's pleasure
pathway. Stimulants such cocaine block the natural re-uptake of dopamine
which otherwise takes place in the clefts between brain cells, boosting
local dopamine levels.

Opiates, nicotine, cannabis and the benzodiazepines all have their specific
receptor sites by which they attach to the brain. Alcohol does not have a
specific docking-site of its own, but works through a wide impact on
natural transmitter systems. With the miracles of modern brain imaging one
can see what parts of the brain light up with what intensity, in what time
sequence, under the influence of any particular drug.

As these effects create addiction, tolerance sets in so that more has to be
taken to get the same high. Withdrawal symptoms complicate the picture, so
drug abuse offers relief from the punishment of cold turkey.

Heroin, cocaine and nicotine top the dependency league, while alcohol has
significant dependency potential with something like 10 per cent of men
becoming dependent over a lifetime. In general, a mind-acting drug which
can give rise to withdrawal symptoms will have the capacity in induce
dependence, notably heroin, alcohol and benzodiazepines. However, the
converse is not always true, so a drug can be highly addictive without
causing bad withdrawal symptoms, as is the case with cocaine.

Until a few years ago the accepted wisdom was that cannabis is that rare
thing, a mood-enhancing drug without significant dependence. Not so. Prof
Edwards says it causes withdrawal symptoms - craving, disturbing dreams,
headaches, shakiness and muscle spasms - and estimates that about 10 per
cent of people who have used cannabis on four or more occasions will become
dependent.

Dependence itself depends on the route by which a drug is taken. Chewing
cocaine or swallowing a drug is less risky than smoking or snorting it,
while injecting is generally the quickest way to induce dependence. Inject
heroin regularly for a few weeks and the drugs ecology will be pushed out
of kilter, making a casual user dependent. The same goes for individuals
who switch from chewing tobacco to smoking it. Substitute injectable
heroin for smoked opium and abuse will sweep across continents, he said.

Just as similar species fare differently in the rainforest as a consequence
of genetic nuances, so people react differently to drugs. A Swedish study
showed that if one non-identical twin was an alcoholic, the risk of the
other being dependent was 32 per cent, while the corresponding figure for
identical twins was 71 per cent. This "suggests a significant genetic
influence".

A recent American study of twins has shown that genetics also help
determine whether an individual finds the experience of smoking cannabis
rewarding and whether, after experimentation, they will persist. Another
much talked about vulnerability is an "addictive personality".

This has little scientific support, he said, but someone with any kind of
problem which makes them unhappy with themselves, easily stressed, given to
thrill-seeking or the casual breaking of rules, will be at greater risk of
substance misuse than the happy conformist person next door.

Just as the rainforest depends on a supply of food, so the likelihood of
any individual being drawn into addiction depends on the drug supply. In
19th century Britain, for example, the use of opium in patent medicine form
or in alcoholic solution, as laudanum, was widespread, with one estimate
suggesting 127 doses per head of population, said Prof Edwards.

Various strands of evidence point to the commonly overlooked ecological
fact that "more people will use more of their favoured drug if it is easier
to find someone who will sell you heroin, if you don't have to walk so far
in the rain to get a drink, or tobacconist is willing to sell single
cigarettes to a 14 year-old".

This was forgotten when Britain adopted continental opening hours, and is
neglected in the current debate about legalisation of drugs where the
complex ecology of abuse is rarely discussed by the media.

"The intrinsic dangerousness of drugs is also downplayed," he says.
"Cannabis, for instance, is not a harmless drug but is dependence-inducing,
can cause bronchitis, can probably cause certain cancers, can impair
executive brain function, can result in short-term mental illness of
sufficient severity to lead to hospital admission, can perhaps impair
driving ability, will destabilise treated schizophrenia." The media
obsession with the simple question of whether to legalise cannabis is, he
concludes, banal and unproductive. (END)

Griffith Edwards is Emeritus Professor of Addiction Behaviour at the
Institute of Psychiatry, London University.