Sativex and Behavioral-relapse Prevention Strategy in Cannabis Dependence

All participants will receive a combination of pharmacotherapy (Sativex or Placebo) associated with a weekly intervention of combined Motivational Enhancement Therapy and Cognitive Behavioral Therapy.

Study subjects will gradually increase the maximal allowed dose of Sativex starting at five sprays per day for the first two days and increasing of five sprays per day until reaching the max number of 42 sprays maximal per day at end of week 2 (Day 11). The target quit date will be set at Day 21 (but subjects will be allowed to stop using cannabis before if they are willing and able to). The medication treatment phase will then be continued for an additional 9 weeks (the last week will be a reduction phase with the use of Spray that will be decreased by 50% to avoid abrupt withdrawal). Then exposure to medications will be stopped (so there will be a total of 12 weeks medication treatment exposure).

Study subjects will gradually increase the maximal allowed dose of Placebo starting at five sprays per day for the first two days and increasing of five sprays per day until reaching the max number of 42 sprays maximal per day at end of week 2 (Day 11). The target quit date will be set at Day 21 (but subjects will be allowed to stop using cannabis before if they are willing and able to). The Placebo treatment phase will then be continued for an additional 9 weeks (the last week will be a reduction phase with the use of Placebo Spray that will be decreased by 50%). Then exposure to Placebo will be stopped (so there will be a total of 12 weeks Placebo treatment exposure).