Once Cannabinoids begin their life growing on the exterior of the Cannabis plant they begin the slow process of degradation. Many Cannabinoids begin in their acidic form and throughout their life, along with a little help from light, air or, you guessed it heat, degrade into other Cannabinoids.
There is one degradation that we don’t speak of very often. Mature THC will degrade into CBN, a Cannabinoid which is far less psychoactive but much more sedating. If you are constantly searching for cultivars to help you fall asleep and you are not having much luck, try taking a few grams of one of those strains and pop it into a clear glass container or plastic bag. Place that container in front of a window, out of reach from your kids, pets and friends with sticky fingers, leave it there for a few days and give it a try, if it is still not sleepy enough for you, put it back in the sun and try again a few days later.