Netherlands National Drug Monitor - Research and Documentation ...

use, particularly cannabis, under-reporting of drug use is less likely in the Netherlands
than in countries with a more repressive policy where legal and/or social sanctions
are attached to drug use. At the same time, it is suggested by the National Prevalence
Survey 2005 (NPO) on substance use in the general population, that illegal
drug use is a sensitive topic in the Netherlands too (Rodenburg et al., 2007). Also
of importance is the extent to which the recruited respondents actually participate
in the survey. This can range from less than 50% to almost 100%. A low response
rate may undermine the reliability of the findings.
Trends in the prevalence of substance use are often difficult to quantify on account
of the numerous interacting factors that may be of influence. Examples are national
and international policy; effective interventions; the production, availability and
accessibility of drugs and other substances; economic factors (such as income);
perceived risks of use; the social environment; and culture, lifestyle and fashions,
and the role that substance plays in these.
Problem substance use
There is no single prevailing definition of the term ‘problem use’. The EMCDDA
defines problem drug use as injecting drug use or long-term/regular use of opiates,
cocaine and/or amphetamines. This is a broad definition which also covers hard
drug users who use methadone, for instance, and are able to function well in
society. Throughout the Netherlands, a wide range of definitions is used at local and
national level. Comparisons therefore have to be made very cautiously. For other
substances, such as cannabis and alcohol, the criteria for misuse and dependence of
international classification systems such as the DSM or the ICD are often used.
For research on substance use in the general population, respondents are generally
selected by random sampling from the population register. This means that
marginalised groups, such as chronic hard drug users, who are regularly admitted
to institutional care or have no fixed address, are greatly under-represented in this
type of research. Therefore, a number of special techniques have been developed,
in order to estimate the numbers of hard drug users. Examples are the capturerecapture
method and the ‘multiplier’ method. These methods are based on the
assumption that a certain percentage of the drug users is known to the police and/
or health care services and registered as such. Others have no contact with these
organisations and are known as the hidden population. Specific statistical techniques
are used to estimate this group as well, in order to arrive at a total estimate of the
number of problem users. It should be borne in mind that prevalence estimates of
this kind allow a considerable margin of error and are generally not very accurate.
Treatment Demand
A certain number of problem users of alcohol or drugs seek treatment from an addiction
care organisation or are admitted to hospital. Data about the numbers of these
1 Introduction
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