“…There is extensive and contradictory literature pertaining to states of ‘khat-induced’ psychoses and schizophrenia-type disorders (Alexander et al., 2010; Hassan et al., 2007; Litman et al., 1986; Numan, 2004; Odenwald et al., 2005). The majority are case reports, which cannot demonstrate a causal relationship (Alem and Shibre, 1997; Anderson et al., 2007a; Critchlow and Seifert, 1987; Dhadphale et al., 1981; Giannini and Castellani, 1982; Gough et al, 1984; Jager and Sireling, 1994; Kalix, 1984; McLaren, 1987; Maitai and Dhadphale, 1988; Mion et al., 1997; Nielen et al., 2004; Odenwald, 2007; Pantelis et al., 1989; Stefan and Mathew, 2005; Warfa et al., 2007; Yousef et al., 1995). A systematic review of the literature suggested that the case report evidence was distorting the scientific debate and was not reflecting the population-based risk of psychosis among khat consumers (Warfa et al., 2007).…”