The main psychoactive component of marijuana, delta-9- tetrahydrocannabinol (THC), strain but, in general, much of the medical cannabis that Canadian licensed growers plan to sell appears to be quite potent. In a June 2014 commentary in CMAJ, two physicians suggested that, based on available clinical evidence, prescriptions should specify that THC concentrations not exceed 9%.
As can be seen on this graph, displaying the potency of the products listed on the websites of five growers, very few strains contain THC concentrations of 9% or lower, assuming these figures are accurate.
Also of note: most of the strains on the websites of growers that offer only a few products (like CanniMed and Bedrocan) have distinct THC concentrations. Those with more extensive catalogues list many strains with similar THC levels. Cannimed (5 products) told CMAJ that many of the strains sold by companies with wide selections are so similar — high in THC, low in cannabidiol (CBD) — that they offer no unique therapeutic benefits. But Tweed (23 products) suggested to CMAJ that there is much more to cannabis than just THC and CBD. There are more than 400 components in cannabis, the grower noted, and it’s possible that varying those components could offer therapeutic benefits, even if THC levels are similar.
Of course, there is little clinical evidence yet to support either claim, which may explain why conversations about the specific medical benefits of marijuana tend to be peppered with a particular word: “anecdotally.”