The medical use of marijuana is surrounded by a cloud of social, political and religious controversy, which obscures the facts that should be considered in the debate. This is a summary of what we should know about marijuana from evidence-based medicine - the harm it may do and the relief it may bring to patients. The book seeks to help the reader understand not only what science has to say about medical marijuana but also the logic behind the scientific conclusions. The work addresses the science base and the therapeutic effects of marijuana use for medical conditions such as glaucoma and multiple sclerosis. It covers marijuana's mechanism of action, acute and chronic effects on health and behaviour, potential adverse effects, efficacy of different delivery systems, analysis of the data about marijuana as a gateway drug, and the prospects for developing cannabinoid drugs. The book evaluates how well marijuana meets accepted standards for medicine and considers the conclusions of other blue-ribbon panels.