Chronic use of ketamine can lead to cognitive impairments, according to a study published in the journal Addiction.
The study was conducted by psychologists and psychopharmacologists at the University College London and published in 2009.
90 ketamine users, 30 users of other drugs, and 30 non-drug users were given psychological and cognitive tests and then re-tested twelve months later. Of the original 150 participants in the study, 80% reported back for re-testing.
According to the authors, increased ketamine use was associated with increased impairments in spatial working memory, pattern recognition memory, and verbal memory. Those who used ketamine more frequently were also more likely to have depressive symptoms than those who used ketamine less frequently.
Morgan, C.J.A., Muetzelfeldt, L., & Curran, H.V. (2009). Consequences of chronic ketamine self-administration upon neurocognitive function and psychological wellbeing: a 1-year longitudinal study. Addiction, Vol105: 121–133