The Stichting Institute of medical marijuana (SIMM), the first company to sell marijuana through the pharmicies of Holland, has been investigating the medical possibilities of cannabis, together with TNO laboritories and the University of Leiden.
One of their discoveries has been that to keep the ripe plants in the dark before harvesting could increase their potency.
SIMM's growers separated a crop of mature plants, harvested half of them and kept the other half in absolute darkness for 72 hours before cutting and drying.
Analysis of the resulting dried buds showed that some varieties had seen increases of THC of up to 30 %, while the CBD and CBN remained the same.
In nature there is no form without function. Cannabis plants do not create THC so we can smoke their buds and get high. Trichomes, and the sannabinoids and terpenoids in them, are a defense against various things. THC works as a sunscreen to protect the delicate inner glands in glandular trichome heads. During each period of light some THC is degraded and then during the next period of darkness that amount of lost THC is replaced plus a small amount more is added. That is the reason why adding UV-B lighting to indoor grows increases the level of THC.
To make this as simple as possible let's say there are 'particles' of THC within a glandular trichome head, let's say there are 10 THC particles. During hours of light say 3 of the 10 particles of THC are degraded leaving 7 'particles' of THC. During the next period of darkness those 3 degraded 'particles' of THC will be replaced and an additional 2 will be added, meaning there are now '12 particles' of THC for when then next period of light begins. That process is repeated over and over again during the flowering stage of growth causing a slow but ever increasing number of THC 'particles.'
When plants are given an extended period of darkness the plants do not have the daily loss, the daily degradation, of THC as it protects the delicate inner glands from UV-B light waves. Plus the plants are in their 'night function mode' where more THC 'particles' are being produced than during the day. So over the 72-hours you have no loss of THC due to light degradation and at the same time you have the 'night function' increased rate of production of THC occurring. The two combine for what can, in some strains, be a significant increase in levels of THC, and a lesser increase in other strains. Like so much in growing it appears to be strain dependent on just how great of an increase there will be, but there will be an increase. It might be so little that it could only be detected using gas chromatography coupled with mass spectrometry and it might be great enough to knock your socks off.
All someone can do is try it and see if it is worth doing with the strain or strains they grow.