Khat is a flowering evergreen shrub native to East Africa. Fresh leaves have been chewed by Africans to take advantage of their stimulant properties for centuries, and khat is also exported to other regions of the world. Due to concerns about its potential addictive qualities, it is considered a controlled substance in many nations, and some have an outright ban to restrict imports.
Africans have been chewing the oval dark green leaves of khat since at least the 11th century CE, when Muslim travelers in Africa wrote about its use as a social drug in the regions they visited. Khat appears to have originated in Ethiopia or Yemen, and because the leaves must be consumed fresh for their effects to be felt, it probably spread slowly across Africa, with people bringing back plants to grow and then introducing their regions to it.
Several compounds in khat appear to be responsible for its stimulant effects, the most potent of which is cathinone. Cathinone has a similar chemical structure to amphetamine, and like other stimulants, khat causes feelings of euphoria and high energy; it can also cause hallucinations. Historically, people took it to stay alert while traveling and working, and the leaves were also chewed after heavy nights of drinking to dispel headaches. In some parts of Africa, the leaves are consumed by groups of men as a social activity.
When people chew khat, they crush the leaves and then tuck them into their cheeks, periodically chewing them again to release more of the active ingredients. It can also be turned into tea or sprinkled on food. As a general rule, the leaves are only good for around 48 hours after harvest, which explains why it was largely restricted to Africa until the late 20th century, when advanced air transport made it possible to overnight the drug to other regions.
Catha edulis, as khat is formally known, has not been studied as extensively as some other controlled substances. Its effects are clearly documented, but researchers are not as sure about its addictive properties. It certainly shares enough traits with amphetamine to be potentially addictive, and long term users do seem to experience some addictive symptoms, but some people feel that further study is needed.
In nations where khat is a controlled substance, African immigrants are sometimes permitted to apply for permits to import it, under the argument that it is an important part of their cultural traditions. In regions with bans, smuggling can be a profitable business, when the smugglers don't get caught.