The goal of the proposed study is to evaluate the efficacy and safety of dronabinol in individuals with obsessive-compulsive disorder (OCD) or the obsessive-compulsive spectrum disorders, trichotillomania (TTM) or pathological skin picking (PSP). Fifteen patients with OCD, TTM, or PSP will receive 12 weeks of open-label treatment with dronabinol. The hypothesis to be tested is that dronabinol will be effective and well tolerated in patients with these disorders. The proposed study will provide needed data on the treatment of a disabling disorder that currently lacks a clearly effective treatment.

The study consists of twelve weeks of open-label dronabinol. All eligible study subjects will be started on open-label dronabinol 2.5mg/day for 3 weeks. The dose will be increased to 5mg/day at visit 2 (Week 3), to10mg/day at visit 3 (Week 6), and to 15mg/day at Visit 4 (Week 9) unless clinical improvement is attained at a lower dose (clinical improvement will be assessed by the investigator with respect to obsessive thoughts, urges and compulsive behaviors). Subjects will be seen every three weeks during the 12-week, open-label study. All efficacy and safety assessments will be performed at each visit. Subjects who are not compliant with their use of study medication (i.e. failing to take medication for three or more consecutive days) will be discontinued from the study.

Laboratory testing, including liver function tests, a blood chemistry panel, and urine toxicology will be completed for subjects at baseline if in the opinion of the study physician the medical history of the subject warrants such tests for their safety. All females, regardless of age, will undergo a urine pregnancy test at screening and all subjects will be required to do a urine drug screen at the screening visit to test for drugs of abuse.

At study conclusion, subjects will be given the option to continue on medication (via prescription) if covered by insurance, and will then be followed in our clinic or referred to another psychiatrist. All study subjects will be offered follow-up care with CBT and/or medication in our outpatient clinic (if covered by insurance) or be given a list of appropriate referrals in the community.

Inclusion Criteria:

1. Age 18-65 years
2. Obsessive-compulsive disorder (OCD), Trichotillomania (TTM), or Pathological Skin Picking (PSP) as the primary psychiatric diagnosis
3. (If OCD) - Subject reports ≥two failed treatments using selective serotonin reuptake inhibitors (SSRIs) for their OCD
4. Women's participation required negative results on a beta-human chorionic gonadotropin pregnancy test and stable use of a medically accepted form of contraception.
5. Signed informed consent before entry into the study.

Exclusion Criteria:

1. Unstable medical illness or clinically significant abnormalities on laboratory tests or physical examination at screening visit
2. Current pregnancy or lactation, or inadequate contraception in women of childbearing potential
3. A need for medication other than dronabinol with possible psychotropic effects
4. History of hypersensitivity to any cannabinoid or sesame oil
5. Lifetime history of bipolar disorder type I or II, dementia, or schizophrenia as determined by the Structured Clinical Interview for DSM-IV
6. Current (past 12-months) DSM-IV substance abuse or dependence
7. Positive urine drug screen at screening
8. Initiation of cognitive behavior therapy within 3 months prior to study baseline
9. Baseline score of ≥ 17 on the Hamilton Depression Rating Scale (17-item HDRS
10. Suicidality based on clinical interview
11. History of head injury or neurological disorder (such as seizures)