It seems to be the pattern for governments that clearly favour synthetics and pharmaceuticals over plants. From the times of the ancient Chinese and ancient Egyptians through Romans and Culpeper's Herbal until 1971 cannabis was used as a medicine. But in 1961 and then in 1971 in the UK, cannabis was suddenly deemed to have no medical uses and possession, cultivation etc was banned. Nowadays Bedrocan is grown and sold through pharmacies in Netherlands and prescribed in other countries, Sativex a whole-plant extract marketted almost worldwide (both produced by pharmaceutical companies, pharmers, not farmers), as a medicine is now available in many US States and in fact USA has been supplying it to a very few patients for decades whilst all the time burning crops, arresting growers and claiming it has no medical use in international treaties and many country's national legislation. That reveals the hypocrisy and corruption of the governments we have elected.
please see http://weedfinder.com/dash/news/censored-1947-cannabis-study-on-epilepsy/