http://apt.rcpsych.org/cgi/content/full/9/6/456"Ethiopia is thought to be the country of origin of khat use. The chewing of khat leaves probably pre-dates the use of coffee. The earliest written record of the medical use of khat appears to be in the New Testament. Khat has been used to treat various ailments, including relieving the symptoms of depression. Some believe it to be a dietary requirement.
Legal aspects of use
In Kenya, Yemen, Uganda, Ethiopia and Madagascar prohibition has resulted in increased illegal importation. When prohibition was replaced in Somalia by import duty, khat chewing became a very common habit within a few years. In Saudi Arabia khat cultivation and consumption are forbidden and the ban is strictly enforced. However, today, khat circulates freely in all of the above countries. In some countries, khat chewing is allowed, in others it is officially banned but there is no law enforcement (Elmi, 1983). "