Khat, the enervating plant masticated across much of the Middle East and Africa, is contributing to serious mental health issues among London's east African communities, according to a report. The somnolent stare of the regular khat-chewer is a familiar sight for anybody who has travelled to the likes of Nairobi or Addis Ababa, and is increasingly seen on the streets of London. A mild sedative that gives off a reasonably powerful high, the plant's......