Long-term heavy cannabis use: executive summary of research report submitted to the Department of Health

The purpose of this study was to identify and assess patterns of use and problems associated with prolonged heavy use of cannabis. The strategy for doing so involved comparing heavy long-term users with light long-term users.
The hypothesis was that heavy long-term use would be associated with more negative effects than light long-term use.
The study was based on self-report data of perceptions and experiences relating to cannabis use over at least a decade. A sample of 405 long-term cannabis users was recruited across five different areas: Birmingham, Bristol, Glasgow, Inverness and Newcastle. The study was carried out between April 2000 and November 2001.