Even before O'Shaughnessy published his pioneering studies of cannabis, the drug was familiar to European and American practitioners of homeopathy, a branch of medicine based on the principle that like cures like. In 1839, the homeopathy journal American Provers' Union published the first of many reports on the effects of cannabis. [23] In 1842, the New Homeopathic Pharmacopoeia and Posology or the Preparation of Homeopathic Medicines was published from an earlier German text. "To make the homeopathic preparation of hemp," the author explained, "we take the flowering tops of male and female plants and express the juice, and make the tincture with equal parts of alcohol; others advise only to use the flowering tops of the female plants, because these best exhale, during their flowering, a strong and intoxicating odour, whilst the male plants are completely inodorous." [24]

Cannabis was first mentioned as a medicinal agent in a "formal" American medical text in 1843. [25] In 1846, Dr. Amariah Brigham, the editor of the American Journal of Insanity, brought the drug to the notice of American psychiatrists with a review of Moreau's book and experiments. Brigham was very exited about the prospect of using cannabis to treat insanity (homeopathy?), and he sent to Calcutta for some of the drug which he subsequently administered to several patients at the Lunatic Asylum in Utica, New York. "From our limited experience," he concluded, "we regard it as a very energetic remedy, and well worthy of further trial with the insane, and thank M. Moreau for having called attention to its use." [26]