A decade ago, when Daniele Piomelli went to scientific conferences, he was often the only researcher studying cannabinoids, the class of chemicals that give marijuana users a high. His work often drew sniggers and jokes; but not any more. At the recent annual Society for Neuroscience conference in San Diego last week, scientists delivered almost 200 papers on the subject. Why all the attention? Many scientists believe marijuana-like drugs might be able to treat a wide range of diseases, far beyond the nausea and chronic pain typically treated with medical marijuana. Researchers presented tantalising evidence that cannabinoid drugs can help...