Cannabis, commonly known as marijuana and by numerous other names, is a preparation of the Cannabis plant intended for use as a psychoactive drug and as medicine. Pharmacologically, the principal psychoactive constituent of cannabis is tetrahydrocannabinol (THC); it is one of 483 known compounds in the plant, including at least 84 other cannabinoids, such as cannabidiol (CBD), cannabinol (CBN), tetrahydrocannabivarin (THCV), and cannabigerol (CBG). Cannabis is often consumed for its psychoactive and physiological effects, which can include heightened mood or euphoria, relaxation, and an increase in appetite. Possible side-effects include a decrease in short-term memory, dry mouth, impaired motor skills, reddening of the eyes, and feelings of paranoia or anxiety. Modern uses of cannabis are as a recreational or medicinal drug, and as part of religious or spiritual rites; the earliest recorded uses date from the 3rd millennium BC. Since the early 20th century cannabis has been subject to legal restrictions with the possession, use, and sale of cannabis preparations containing psychoactive cannabinoids currently illegal in most countries of the world; the United Nations deems it the most-used illicit drug in the world. In 2004, the United Nations estimated that global consumption of cannabis indicated that approximately 4% of the adult world population (162 million people) used cannabis annually, and that approximately 0.6% (22.5 million) of people used cannabis daily. Medical marijuana refers to the use of the Cannabis plant as a physician-recommended herbal therapy, which is taking place in Canada, Belgium, Australia, the Netherlands, Spain, and several U.S. states.