i just recently read something on this:
Interrupted flowering
Also known as ``buddus interruptus'', the procedure is to switch the lights to 24/0 for a day or two about at the end of the fifth week of flowering, when the buds seem to stall out. It should only be done once during the crop, and for no more than two days. The best technique is to switch for one day, wait a couple of days to observe the effect, and then give it one more day if the buds haven't responded. This is not the same as ``double budding'', as the plant is never actually kicked into vegetative growth.
If the plants react well, you will see tufts of additional flowering parts standing out from the sides of the buds like little towers. Done early enough, these extra parts should finish in time, and they will add extra weight to the crop. This technique can be particularly valuable in scrog, given the large number of smaller buds.
A caveat is in order, not all plants respond well. Some don't react to the light change at all, and a very few may be disturbed into uncontrolled growth from the tops of the buds. You might be concerned with a tendency for male parts to be produced, but I've been practising this method for a long time, and I've never seen a ``hermie''.
This will not add extra THC, it will only add extra weight to the plant. if you want 'extra' THC you will need a plant that has a proven genetic record of high crystal content. then, you must add a good UVB lamp to your setup- that will ensure your crystals mature from precursers to THC molecues.