Working memory and speed of information processing in chronic khat users: preliminary findings.

To date there are very few laboratory data available regarding the long-term effect of the psychostimulant khat on human neurocognitive functioning. The purpose of the present study was to assess whether chronic khat users would demonstrate impairments in working memory and speed of information processing compared to control subjects. Working memory was assessed using the forward and backward digit span test. Speed of information processing was assessed using the Digit Symbol Substitution Test. Results of the present study indicate that chronic khat use may have a long-term deleterious effect on working memory, particularly on digit backwards measures of short-term/working memory. The finding is consistent with results seen by several investigators in samples of methamphetamine users.