Original sentence: , CBD, CBN, and CBC) showed no significant change in their concentration over the years"
Edited sentence: , CBD, CBN, and CBC) showed no significant change in their concentration over the years".. More recent research undertaken at the University of Mississippi's Potency Monitoring Projecthas found that average THC levels in cannabis samples between 1975 and 2007 have increased from 4% in 1983 to 9.6% in 2007