Neil McKeganey: News is encouraging, but we need to see whole picture before getting carried away

REPORTS of a dramatic fall in the availability of heroin in Scotland will be regarded by many as a positive development, but we should be careful before celebrating too long.

The evidence on which this report is based is not as strong as many may think. The finding that fewer drug users are testing positive for heroin after their arrest is encouraging and suggests the drug may not be as widely available as in the past.

The Serious Organised Crime Agency (Soca) is trumpeting these results as an indication of the successes of upstream disruption - basically, stopping heroin getting into the UK by tackling it nearer production and transportation countries.

Over the past few years, however, we have seen a marked decrease in the quantity of heroin seized.

We need to be cautious since Soca has not actually released any figures showing a dramatic increase in seizures.

But is seizing heroin a good thing? It is if it succeeds in reducing the availability of the drug. Unfortunately, most addicts still say they have no difficulty in accessing the drug.

We know that addicts' risk of overdose increases where the purity of heroin fluctuates. Any reduction in heroin is likely to lead to a decrease in purity. This does raise the possibility of an increase in addict deaths if the level of heroin purity were to revert to its previous level.

It may be, if heroin starts to become less available, that cocaine may increase in popularity. If cocaine were to replace heroin as Scotland's main drug of abuse, we could expect to see a marked increase in violence.

When seizures are effective, they disrupt the life of the addict and can lead to an increase in other problems. But we should never let those possible difficulties dissuade us from doing all we can to reduce the availability of illegal drugs.

• Neil McKeganey is professor of drugs misuse research at Glasgow University.