Table 1.

Studies demonstrating evidence of cognitive impairments induced by regular khat use or synthetic cathinones in human subjects.

Drug	Use patterns	Cognitive deficits	Reference
khat	daily, almost daily or occasional use	↓ visuoperceptual memory and fluency, spatial memory, short and long-term memory	(Khattab and Amer 1995)
	≥1 yr regular use	↓ response inhibition	(Colzato et al. 2010)
	≥1 yr regular use	↓ cognitive flexibility, working memory	(Colzato et al. 2011)
	≥1 yr daily use	↓ working memory, n.c. information processing speed	(Hoffman and al’Absi 2013b)
	≥1x week, >1 yr	↓ serial learning, psychomotor speed, set-shifting	(Ismail et al. 2014)
mephedrone	>1 yr of regular use	↓ verbal recall and fluency	(Freeman et al. 2012)
	<48 hr prior to psychological test	↓ verbal recall and fluency	(Herzig et al. 2013)
	≥1x month; self-reported use examined over 9 d	↑ self-reported cognitive impairment (unspecified)	(Homman et al. 2018)
	≥6x prior use;; acute 200 mg dose administered p.o.	↓ short term memory, n.c. divided attention effects not counteracted by alcohol (0.8 g/kg)	(de Sousa Fernandes Perna et al. 2016)