Cognitive impairment in Khat users

Our brains are impaired enough already so make sure you lay off the khat.
http://tlneuro.wordpress.com/2012/03/27/cognitive-impairment-in-khat-users/
A recently published study examines the cognitive effects of khat (Catha edulis) chewing. Colzato and colleagues (2011) recruited 20 khat users with 10.5 (6.5 SD) years of use, averaging 3.1 (1.8 SD) times per week. The average time spent chewing khat in each session was 5.8 hrs (1.7 SD) and all khat users met at least four criteria which define addiction under DSM-IV or ICD-10 criteria. Marijuana consumption in these individuals and the khat-free controls was about 2 joints per week, they consumed 6-8 drinks per week and had zero lifetime exposure to cocaine, amphetamines or ketamine. Subjects were also matched on IQ (using the Ravens Standard Matrices), age (~31 years), ethnicity/origin (all African) and sex (2 female in each group), although two male subjects from the khat-user group had to be excluded for excessive error rates in the switching task