According to Florida-based Novus Medical Detox, today's marijuana is much more potent than the varieties available a generation ago. This poses significant health risks to consumers as the wave of legalization gains momentum.
In a study by the University of Mississippi Potency Monitoring Project, the level of weed's main psychoactive ingredient, THC, has increased from 3.4% in 1993 to ~9% in 2008. In sinsemilla (the flowering tops of unfertilized female plants) THC levels have jumped from 5.8% to 13.4%. The lab has identified THC concentrations as high as 37% in certain pot strains.
The controversy surrounding the legalization of marijuana will no doubt intensify as the health risks of consuming ever-higher levels of THC in cannabis become more widely known.