"The Stichting Institute of Medical marijuana (SIMM), the first company to sell marijuana through the pharmacies of Holland, has been investigating the medical possibilities of cannabis, together with TNO laboratories and the University Leiden."

There has only been a small research effort into the subject of darkness before harvest, but it produced some interesting results. They found that seperating their crops and harvesting half after 72 hours of darkness, showed upwards of 30% increased THC in "some" strains. CBN and CBD were no different.

At night plants follow a cyclic function that operates differently compared to during the day. They accurately and mathemetically calculate how much photosynthate to burn for their duration of darkness. This calculation has been observed in plants and that they can accurately utilize photosynthate so that it is almost completely exhausted before light arrives. After which so a unanticipated duration of dark would send a plant into starvation mode.

The exact relationship of THC production is not completely understood, but it has been thought that it is used to protect itself from light. As such THC degrades with light and is continously being produced. So it might be plausable that darkness before harvest increases THC levels in plants, but i would anticipate based on current research that this effect would not be well benefitted past the standard 12 hours of darkness. As it has been shown plants degrade 95% of their stored resources by the time of their calculated night cycle is nearly finished.

I would personally still use 24hrs or more of darkness before harvest, as there are other properties that are of benefit.