After going from a chalky color to an amber color, the trichomes actually start to degrade and THC will begin to convert to CBD, and other compounds. More of a THC high will produce an upbeat, social stone...while more CBD will just glue you to the couch. At least, I think that's how it works.

Sativas and indicas are primarily different in the way the plants grow, including flowering time, node formation, bud structure, amongst other things. They all produce THC in the end, in which the same trichome circumstances would still apply.