Neurocognitive profiles of methamphetamine users: Comparison of those with or without concomitant ketamine use

Objective: Methamphetamine (MAMP) and ketamine are neurotoxic drugs whose chronic use has been linked with a cognitive decline in some users. This paper aims to assess the possible effect of concomitant ketamine use on the neurocognitive performance of MAMP users. Methods: This study divides 42 MAMP users into MAMP users who use ketamine (MAMP+K, n = 16) and MAMP users who do not use ketamine (MAMP-K, n = 26). The performance of these two groups was compared using the Brief Assessment of Cognition in Schizophrenia (BACS), Conners Continuous Performance Tests (CPT), the Wisconsin Card Sorting Test (WCST), the Iowa Gambling Task (IGT), and the Barratt Impulsiveness Scale (BIS). Results: In comparison to the MAMP-K group, the MAMP+K group showed worse performances in verbal fluency, executive function and composite score in BACS; worse performances in total errors, perseverative errors, nonperseverative errors and conceptual level response in WCST; and greater levels of total scores and novelty-seeking in BIS. Neither the attention function evaluated with CPT nor the decision-making behavior evaluated with IGT was associated with previous ketamine use. Conclusion: This study detected worse executive function and higher impulsivity level among MAMP users with additional ketamine use versus their counterparts without ketamine use. Further studies with a longitudinal design and a large sample size are necessary to clarify the connection between cognitive deficits and concomitant use of MAMP and ketamine.