The National Institute of Drug Abuse (NIDA), in its July 2005 "Research Report," stated:

“Research is underway to examine the effects of smoked marijuana and extracts of marijuana on appetite stimulation, certain types of pain [including arthritis], and spasticity due to multiple sclerosis. However, the inconsistency of THC dosage in different marijuana samples poses a major hindrance to valid trials and to the safe and effective use of the drug.

Finally, little is known about the many chemicals besides THC that are in marijuana, or their possible deleterious impact on patients with medical conditions.”

July 2005