Studies have shown that vaporizing cannabis exposes the user to lower levels of harmful substances than smoking cannabis. These findings are important for it is estimated that 10-20 percent of patients with chronic pain, multiple sclerosis, epilepsy, and HIV/AIDS have admitted to smoking cannabis for therapeutic purposes. For patients, a study found that smoking cannabis sativa reduced daily pain by 34%, a statistically significant amount.
In a study published in the Journal of Psychopharmacology in May 2008, it was stated that vaporizers were a "suitable method for the administration of THC". A 2007 study by the University of California, San Francisco, published in the Journal of the American Academy of Neurology, found that "there was virtually no exposure to harmful combustion products using the vaporizing device". A 2006 study performed by researchers at Leiden University found that vaporizers were "safe and effective cannabinoid delivery system(s)". The study stated that the amount of THC delivered by vaporizers were equivalent to the amount delivered by smoking. Because of those studies and other studies, vaporizers are medically sound devices for delivering THC.
The proposed factors affecting output include:
- Specimen density
- Weight, content of water and essential oils
- Consistency of material in the filling chamber
- Storage time of the vapor
- Inhalation method (breathing technique)
Not all those have been scientifically tested. Research using vaporizers found the delivery efficiency highest at around 226 °C (439 °F), falling to about half efficiency at 150 °C (302 °F) to 180 °C (356 °F) degrees depending on material. The purest preparations produced the highest efficiencies, about 56% for pure THC versus 29% for plant material (female flower tops) with 12% THCA content. Besides THC, several other cannabinoids as well as a range of other plant components including terpenoids were detected in the plant material. Using pure THC in the vaporizer, no degradation products (delta-8-THC (D8-THC), cannabinol (CBN), or unknown compounds) were detected by HPLC analysis. The longer vapor is stored, the more THC is lost as it condenses on the surface of the vaporizer or the balloon. This loss may be negligible over a few minutes but may exceed 50% after 90 minutes. The Leiden University study found that as much as 30–40% of inhaled THC was not absorbed by the lungs but simply exhaled. However, they did not find large individual differences in the amounts exhaled.