Investigators at the Rockland Psychiatric Center in Orangeburg, New York, and the New York University School of Medicine, administered 2.5 to 5 mg doses of oral THC (dronabinol) for a period of eight weeks to six patients diagnosed with chronic, refractory schizophrenia. All of the patients enrolled in the study had reported previously using cannabis to mitigate their condition.

"Four of the 6 patients improved to a clinically significant extent (after taking dronabinol)," researchers reported. "Three of the six patients had a robust response, with modest to marked reductions in core psychotic symptoms. Patients 1 and 2 showed improvement within several weeks of beginning the medication, whereas patient 3 required 8 weeks to reach significant improvement. In addition, robust improvement in overall functioning was also observed, with patients 1 to 3 changing from being gravely ill to being functioning individuals able to be discharged. Patient 4 had more limited improvement in that he was calmer, cooperative, and less aggressive but had persistence of his core psychosis. Nevertheless, his overall functioning was significantly improved. ... There were no clinically adverse effects."

Investigators concluded, "These results ... open a possible new role for cannabinoids in the treatment of schizophrenia."

Previous studies assessing the use of marijuana in patients with schizophrenia have produced mixed results. A 2007 German study reported improved cognition in patients who used cannabis, and a 2008 Australian study found that patients diagnosed with schizophrenia report experiencing subjective relief from pot. Critics of medical cannabis use have argued that heavy marijuana use may exacerbate psychosis in patients with mental illness. However, the largest trial ever conducted comparing cannabis using and non-using schizophrenic patients reported no statistically significant "differences in syptomatology between schizophrenic patients who were or were not cannabis users" after controlling for patients' age, sex, and ethnicity.

For more information, please contact Paul Armentano, NORML Deputy Director, at: paul@norml.org. Full text of the study, "Synthetic Delta-9-tetrahydrocannabinol (dronabinol) can improve symptoms of schizophrenia," appears in the June issue of the Journal of Clinical Psychopharmacology.