Identifying the co-occurrence of drug use and mental health disorders in the same individuals is essential for effective treatment of their drug use problems. Reviewing the available information on psychiatric co-morbidity among drug users in European countries, the paper shows that there is a need to establish guidelines to collect comparable information across Europe.

Table of contents:
• Introduction
• Sources of information
• Prevalence and nature of co-morbidity
• Prisoners: an example of a vulnerable group
• Limitations
• Annex
• References
• Acknowledgements