Cognitive performance of current methamphetamine and cocaine abusers.

Forty currently using methamphetamine (MA) abusers, 40 currently using cocaine (COC) abusers, and 80 comparison participants who did not use psychostimulants received a cognitive battery and questionnaires covering medical history and stimulant use patterns. Forty comparison participants were matched to the 40 MA users on age, education, ethnicity, and gender. The other 40 comparison participants were matched to the cocaine users on the same variables. This design was chosen because there were significant differences in age and ethnicity between COC and MA users that precluded a direct comparison between the groups. The COC group was older and predominantly African American compared to the predominantly Caucasian MA group. When compared to their matched non-using control groups, both MA and COC abusers were impaired on cognitive measures, but the type and degree of impairments were somewhat different.