Good question. I know that providing the spectrum of light that plants need it, when they need it is the most efficient use of light photons. The UVA diodes within the plant stress the plant slightly. The plant responds to that stress creating sunscreen which is everything we want out of dank weed....essential oils, flavonoids, terpenes, trichomes, THC & CBD. I have read however UVB which is not included may in fact decrease CBD's.