Pilot Study Repetitive Transcranial Magnetic Stimulation (rTMS) in Cannabis Craving

Primary objective: Repetitive transcranial magnetic stimulation (rTMS) provides a non-invasive means of altering brain neural activity. This pilot study will test whether 5 days of rTMS reduces cue-induced cannabis craving and use in cannabis users. Hypothesis: We predict that active rTMS will significantly lower craving for cannabis compared with sham rTMS. Study population: Thirty healthy adult cannabis users (for at least 2 years, currently averaging 3 times weekly) with no other major psychiatric disorders except nicotine dependence (DSM IV criteria) will be recruited from the community. Design: Following a baseline phase to evaluate subject characteristics, subjects will be randomly assigned to receive 5 days of active or sham rTMS. rTMS at 1 Hz and strength 120% of the motor threshold will be applied to the dorsolateral prefrontal cortex (DLPFC) using a figure 8 coil , beginning 1 second after presentation of a cannabis-associated visual cue and lasting for 30 seconds. Brain site localization will use a computerized navigation system based on structural MRI scans obtained before the first session. Each rTMS session (lasting around 31 minutes) will consist of 54 trials (cue presentations): 36 with cannabis-associated cues and 9 each with non-drug-associated positive or neutral cues. No rTMS will be administered with the non-cannabis-associated cues. Subjects return for follow-up assessments one and two weeks after the final rTMS session. Outcome measures: The primary outcome measure will be cannabis craving assessed by the Marijuana Craving Questionnaire and visual analog scales before and after every rTMS session and at one- and two-week follow-up. Secondary outcome measures will be self-reported cannabis use and urine drug testing at each rTMS session and follow-up visit, and changes in regional brain responses to cannabis-associated visual cues assessed by fMRI done before and after the 5 rTMS sessions. Benefits: The future benefit to society may be development of better methods for treatment of cannabis addiction. Risks: The primary risks from rTMS are transient headache, scalp discomfort, decreased spatial recognition memory, and hearing loss (minimized by wearing ear plugs). Seizures are very rare when rTMS is administered within accepted safety guidelines and individuals at increased risk of seizures are excluded. The risk of inducing a manic episode is minimized by excluding individuals with a history of non-drug-induced mania/hypomania.