Participants were classified as meeting lifetime criteria for DSM-IV cannabis dependence (American Psychiatric Association, 2000) if they reported three or more of the following symptoms occurring within the same 12 month period: using cannabis a greater number of times/greater amount than was intended, tolerance, wanting to cut down/stop use, spending so much time obtaining/using/recovering from the effects of cannabis the participant had little time for anything else, reducing important activities as a result of cannabis use, continuing use despite it worsening health/emotional problems. Withdrawal was not included as it was not part of DSM-IV criteria for cannabis dependence. Participants were also asked the age at which they first experienced three or more of these symptoms occurring within a 12 month period.
