Achieving Cannabis Cessation-Evaluating N-Acetylcysteine Treatment

Inclusion Criteria: * Age 18-50 years * Must be able to understand the study and provide written informed consent * Must meet current DSM-IV criteria for cannabis dependence in the last 30 days * Must express interest in treatment for cannabis dependence * Must submit a positive urine cannabinoid test during screening * Women of child bearing potential must agree to use appropriate birth control methods during study participation: oral contraceptives, contraceptive patch, barrier (diaphragm or condom), levonorgestrel implant, medroxyprogesterone acetate, complete abstinence from sexual intercourse, or hormonal contraceptive vaginal ring Exclusion Criteria: * Allergy or intolerance to N-Acetylcysteine * Women who are pregnant or lactating * Current use of NAC or any supplement containing N-Acetylcysteine (must agree not to take any such supplement throughout study participation) * Use of carbamazepine or nitroglycerin within 14 days of randomization * Current enrollment in treatment for cannabis dependence * Any use of synthetic cannabinoids (such as K2/Spice) in the 30 days prior to screening or during the period between screening and randomization * Current substance dependence, other than cannabis or nicotine * Urine drug screen positive for any drug of abuse other than cannabis or amphetamines at the randomization visit (Only participants who have a valid prescription for amphetamines (e.g., for ADHD) may be included) * Urine drug screen positive for amphetamines at the randomization visit without having a valid prescription for it * Maintenance treatment with buprenorphine or methadone * Recent history of asthma (within the last 3 years) * History of seizure disorder, bipolar disorder, schizophrenia, or other significant or unstable medical or psychiatric illness that may place the participant at increased risk in the judgment of the medical clinician * Significant risk of homicide or suicide