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The Dutch penal system could benefit from a more differentiated law enforcement policy towards crack users who primarily sell drugs to support their own use. Moreover, measures to lessen dependency among crack users and address their housing conditions could significantly reduce drug-related crime. These are the key findings of new research by Alberto Oteo Pérez, who will obtain his doctorate from the University of Amsterdam (UvA) on Wednesday, 18 May.


Today, crack is the primary drug for a large proportion of ‘problematic’ drug users in the Netherlands. However, until now there has neither been a reliable estimate nor a representative profile of this population.

Mixed sampling

To fill this lacuna, Oteo Pérez made an estimate of the size of the urban population of frequent crack users in the three largest Dutch cities (Amsterdam, Rotterdam and The Hague) by recruiting more than a 1000 crack users through respondent-driven sampling (RDS), an improved form of ‘snowball’ sampling, and institutional samples. His aim was to assess their socio-demographic characteristics, patterns of use and associated problems, including involvement in drug-related crime, and gain insight into their initial willingness to participate in pharmacological treatments.

Crime and housing

The samples revealed that a significant proportion of crack users participated in the drugs trade chiefly to support their own use. This form of drugs supply, known as ‘minimally commercial supply’, differs from profit-driven drugs supply, which is more often linked to organised crime. Drug dealing was also the most common illegal activity among those taking part in the sample. Moreover, the samples showed a link between criminality and the living conditions of heavier drug users. ‘Based on my findings of crack users’ illegal activities, it seems that lack of housing and financial constraints are strongly related to problematic use and nuisance’, says Oteo Pérez. ‘If the legal system can accommodate this type of supplier and provide for proportionate policies, the potential for rehabilitation and social integration could increase markedly.’

The author also argues for the continuation of current measures at the social care-network level that address these conditions – such as ‘housing first’ initiatives and the allocation of homeless drug users to supervised housing – as well as new forms of treatment. Oteo Pérez: ‘A substantial part of this population remains hesitant to go into treatment, even though many are willing to stop or reduce their use. To increase the chances of a successful intervention, it might a good idea to focus on new forms of maintenance medication to retain crack users in treatment, similar to opiate substitution treatment. Such treatment could be especially effective in reducing crime among crack users who are reluctant to take part in abstinence-oriented interventions.’      


Alberto Oteo Pérez, Urban Crack Users in the Netherlands: Prevalence, Characteristics, Criminality and Potential for New Treatments. Supervisor: Prof. D.J. Korf. Co-supervisor: Prof. V.M. Hendriks.

Time and location

The PhD defence ceremony will take place on Wednesday, 18 May 2016 at 12:00. Location: Agnietenkapel, Oudezijds Voorbrugwal 229-231