I googled this info once upon a time, and what I came across was some info from the Dutch saying that for SOME strains, a period of 72 hours of darkness right before harvest resulted in markedly increased THC production, as much as 30 percent more. But...not all strains, just some, a genetic thing. So, try it. Worst case, it won't help and won't hurt, and best case, more THC production.
"Before you consider one an enemy, first walk a mile in his shoes. Then, if he *is* an enemy, you're a mile ahead, and you have his shoes."