THC and CBD are produced in their carboxylic acid forms in the plant and THCA does not readily pass the blood brain barrier, so it is minimally psychoactive. That is not an issue smoking or vaporizing THCA, because the act of heating it causes it to lose a carbon, two oxygen, and a hydrogen atom, in the form of CO2 and H2O. This changes the polar THCA to non polar THC, by eliminating the COOH group, that makes it an acid.
At the same time that heating changes THCA to THC, it also changes THC to CBN. Depending on the time and temperature that you use for decarboxylation, the rate of THC converted to CBN can equal or exceed the rate that THCA is converted to THC.
Attached is a graph compliments of Jump, showing the relationship of different time and temperature curves to total THC:
I put my cannabis oil in a 250F Canola oil bath and watch the CO2 bubble production to tell precisely when the bubble production suddenly drops off at the top of the 70% curve, which is where maximum THC is preserved.
