well i was reading in an old hightimes mag that the reason for harevsting after a plant has been left in the dark is not so much for a thc increase but during the night a plant sends all the sugars from the leaves and buds to its roots so the can start working to building more plant but if u left it in the dark all the sugars wouldnt return to the plant therefore u would have most nutrients and sugars in your roots so thats a less harsher smoke