Elsevier

The Lancet

Volume 367, Issue 9525, 3–9 June 2006, Pages 1830-1834
The Lancet

Articles
Incidence of heroin use in Zurich, Switzerland: a treatment case register analysis

https://doi.org/10.1016/S0140-6736(06)68804-1Get rights and content

Summary

Background

Switzerland has been criticised for its liberal drug policy, which could attract new users and lengthen periods of heroin addiction. We sought to estimate incidence trends and prevalence of problem heroin use in Switzerland.

Methods

We obtained information about first year of regular heroin use from the case register of substitution treatments in the canton of Zurich for 7256 patients (76% of those treated between 1991 and March, 2005). We estimated the proportion of heroin users not yet in substitution treatment programmes using the conditional lag-time distribution. Cessation rate was the proportion of individuals leaving substitution treatment programmes and not re-entering within the subsequent 10 years. Overall prevalence of problematic heroin use was modelled as a function of incidence and cessation rate.

Findings

Every second person began their first substitution treatment within 2 years of starting to use heroin regularly. Incidence of heroin use rose steeply, starting with about 80 people in 1975, culminating in 1990 with 850 new users, and declining substantially to about 150 users in 2002. Two-thirds of those who had left substitution treatment programmes re-entered within the next 10 years. The population of problematic heroin users declined by 4% a year. The cessation rate in Switzerland was low, and therefore, the prevalence rate declined slowly. Our prevalence model accords with data generated by different approaches.

Interpretation

The harm reduction policy of Switzerland and its emphasis on the medicalisation of the heroin problem seems to have contributed to the image of heroin as unattractive for young people. Our model could enable the study of incidence trends across different countries and thus urgently needed assessments of the effect of different drug policies.

Introduction

Switzerland has been criticised for its liberal drug policy.1, 2 Specifically, the implementation of harm reduction measures, such as drug consumption rooms, needle-exchange services, low-threshold methadone programmes, and heroin-assisted treatments, have been thought to make potential users think that harm will not arise from use of illicit drugs.3, 4 According to this critique, such a policy would lead to a growing number of new users of street drugs and lengthen the period of heroin addiction. Contrary to this belief, stable prevalence of heroin use since 1994 has been reported in Switzerland.5, 6, 7

Prevalence rates are important for estimation of the proportion of drug users who are in treatment, but provide only indirect information about trends in incidence of heroin misuse. Unfortunately, data for incidence as a direct measure of the ongoing spread of drug use are rarely available.8, 9, 10, 11

Zurich is the most populous canton of Switzerland, comprising about a fifth of the country's population with 1 200 000 inhabitants, about 350 000 of whom live in the city. Open drug scenes developed in the early 1980s in the city of Zurich, culminating in 1986–92 at the Platzspitz (“Needle Park”) and in 1993–95 at the former railway station Letten. Drug mortality data indicate that about 25% of Switzerland's heroin users live and die in Zurich.12, 13

Since 1991, in the canton of Zurich there have been no requirements to qualify for substitution treatment other than being heroin dependent. Mandatory health insurance covers the costs of treatment and patients may choose their physician among those who practise in the canton. After special instruction in addiction medicine, any physician, whether working in a private practice or in an institution, may provide substitution treatments with methadone or buprenorphine. Therefore, there are enough treatment slots for all those who apply, at least since 1992.

Since 1991, the Research Group on Substance Use Disorders of the Psychiatric University Hospital of Zurich has been entrusted by the government with the long-term monitoring of substitution treatments in the canton of Zurich. We were therefore able to directly assess whether and how incidence, prevalence, and duration of heroin dependence have changed during past decades.

Section snippets

Database

The Swiss law on narcotics requires registration and evaluation of substitution treatments for opioid dependence.14 Since 1991, our research group has been mandated by the health authorities to operate an anonymised case register of substitution treatments with methadone or buprenorphine. Providers must make anonymised information available at the beginning and at the end of each treatment episode, or at least twice annually. By means of a personal code (initials of first name and last name and

Results

Since the start of the case register in 1991 we have registered 9518 patients who underwent 24 163 treatment episodes up to March, 2005 (uninterrupted substitution treatments by the same provider). Of these, 2996 treatments—provided by 21 institutions and 309 doctors in private practice—were still ongoing in 2005. From 1998, the number of substitution treatments remained stable (between 3094 and 3345 per quarter), whereas the number of patients decreased slightly from 3788 in 1998, to 3698 in

Discussion

The incidence of regular heroin use in the canton of Zurich started with about 80 new users in 1975, increased to 850 in 1990, and declined to 150 in 2002, and was thus reduced by 82%. Incidence peaked in 1990 at a similar high level to that ever reported in New South Wales, Australia, or in Italy. But only in Zurich has a decline by a factor of four in the number of new users of heroin been observed within a decade. This decline in incidence probably pertains to the whole of Switzerland

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