Dronabinol Treatment for Marijuana Addiction

Inclusion Criteria: * men and women between the ages of 18-60 * Meets DSM-IV criteria for current marijuana dependence and reports marijuana as primary drug of abuse * Individuals must report using marijuana at least 5 days a week and have a marijuana positive urine drug screen on the day of study entry * Individuals must be capable of giving informed consent and capable of complying with study procedures. * Women of child-bearing age will be included in the study provided that they are not pregnant, based on the results of a blood pregnancy test drawn at the time of screening. They must also agree to use a method of contraception with proven efficacy and agree not to become pregnant during the study. To confirm this, blood pregnancy tests will be repeated monthly. Women will be provided a full explanation of the potential dangers of pregnancy while on the study medication. If a woman becomes pregnant, the study medication will be discontinued. Exclusion Criteria: * Meets criteria for current psychiatric disorder requiring psychiatric intervention. Disorders that are stable on psychotherapy or pharmacotherapy will not be exclusionary. Individuals will be permitted to take prescribed zolpidem and zaleplon if there is no evidence of dependence on these substances. * History of seizures * Known sensitivity to dronabinol * Unstable medical conditions * Physical dependence on any other drugs (excluding nicotine) that would require medical detoxification * Currently taking psychotropic medication with benefit for any other illness than treatment of insomnia * Pregnant or breast-feeding * Individuals who have exhibited suicidal or homicidal behavior within the past two years or who have current active suicidal ideation. * Individuals with coronary vascular disease as indicated by history of abnormal ECG or history of cardiac symptoms. * Unstable physical disorder which might make participation hazardous such as uncontrolled hypertension (SBP \> 150, DBP\> 90, or HR \> 100 when sitting quietly), acute hepatitis (patients with chronic mildly elevated transaminases \< 2-3X upper limit of normal are acceptable), or medically unstable diabetes. * Subjects in professions in which even mild intoxication would be hazardous (e.g., police officer, bus driver, firefighter). * Individuals who are court-mandated to treatment.