Psychoactive plants are plants, or preparations thereof, that upon ingestion induce psychotropic effects. As stated in a reference work: Psychoactive plants are plants that people ingest in the form of simple or complex preparations in order to affect the mind or alter the state of consciousness. Psychoactivity may include sedative, stimulant, euphoric, deliriant, and hallucinogenic effects. Several hundred psychoactive plants are known. Some popular examples of psychoactive plants include Coffea arabica (coffee), Camellia sinensis (tea), Nicotiana tabacum (tobacco), and Cannabis (including hashish). Psychoactive plants have been used ritually (e.g., peyote as an entheogen), medicinally (e.g., opium as an analgesic), and therapeutically (e.g., cannabis as a drug) for thousands of years. Hence, the sociocultural and economic significance of psychoactive plants is enormous. Many plants contain substances that alter moods and cause euphoria. Some of these psychoactive plants were known to the ancients. The history of poppy cultivation dates back to 3400 BC. In Mesopotamia. Poppies were cultivated by the Egyptians and then spread to India and China. Opium was widely used by Arab physicians around 1000 AD . Opium addiction was rampant in China, and after opium was banned in 1799, opium smuggling became a general industry, and in 1839, the Opium War broke out between Britain and China. The psychoactive plant Cannabis sativa (hemp plant) was already known in ancient China and India 5000 years ago. The earliest reference was found in a pharmacist's book from 2737 BC. It was written during the reign of Emperor Shennong of China. By 1000 AD, hemp products had spread to the Middle East and Africa. Cannabis probably came to South America in the 16th century. In the 19th century, cannabis was used medicinally due to its narcotic effects. Although many scientific articles on the therapeutic value of cannabis were published in Europe and America in the late 19th century, the use of cannabis in medicine declined significantly in the early 20th century.