This is a great unbiased documentary, showing some real scientific studies, and is hosted by an addiction specialist who has dealt with Heroin and Cocaine addicts. Although it does show some Cannabis 'addicts' their behaviour cannot be applied to all cannabis users.
Near the end it also shows the labratory where the drug Sativex is made from cannabis plants.
Cannabis has been used since 3000 BC as a recreational and spiritual drug as well as a medicinal one. The first charred cannabis seeds were found in what is now Romania at a ritual site. The most commonly recognised users of cannabis were the Hindus of India and Nepal. The Aryans introduced the drug to the ancient Assyrians, Scythians and Thracians/Dacians.
In 2008, a 2,700 year old marijuana stash was found in a Gobi Desert grave. Tests on the high potency of the stash shows that the ancients may have used the marijuana plant for its phsycoactive properties as well as using hemp for ropes and clothing.