Most individuals who promote herbs and natural plants for healing feel that there are 2 specific benefits for using the plant as provided by nature instead of synthetically and artificially attempting to isolate a single component and make it into a drug.
These 2 benefits claimed are 1) primary active ingredients work best with the plants additional chemicals, often referred to as the entourage effect or synergism, and 2) the additional chemicals in the plant reduce side effects from the primary active ingredient.
This study was a result of searching Medline from 1966-1999, Agricola from 1990-1999, and Biological and Agricultural Index from 1964-1999. It found that in the case of marijuana with THC considered as the primary active ingredient, there is good evidence to support those above 2 claims that herbalists often make.
In fact, they state that the other compounds found in marijuana besides the THC, increase cerebral blood flow, enhance cortical activity, kill respiratory pathogens, and provide anti-inflammatory activity.
When it comes to using marijuana as natural medicine you may be doing best by using it in its whole plant form as provided by nature.