Drug Use: Effects of ketamine (K) on users

For the study, researchers from University College London followed 150 people over a year to see if changes in their ketamine use could predict changes in their psychological well-being, memory and concentration. Of these 150 people, 30 were taking large quantities of the drug nearly every day, 30 were taking it 'recreationally' (once or twice a month), 30 were former users, 30 used illicit drugs apart from ketamine and 30 did not use any illicit drugs.

The authors found that the heavy ketamine users were impaired on several measures, including verbal memory. Short term memory and visual memory in this group decreased over the year as ketamine use increased. These individuals also performed more poorly overall on verbal memory, displaying symptoms such as forgetfulness and experiencing difficulty recalling conversations and people's names.

The amount of increase in ketamine use over the course of one year was also a source of concern. Hair analysis showed that ketamine levels among recreational users doubled at follow-up compared to initial testing, a pattern seen with other addictive drugs. Ketamine levels in the frequent using group did not change across the year, but this group was already using up to ten grams per day at initial testing.

Interestingly, the recreational ketamine users and ex-ketamine users did not differ from non-drug-taking controls on memory, attention and measures of psychological well-being, suggesting that occasional ketamine use does not lead to prolonged harms to cognitive function and that any damage may be reversed when people quit using the drug. However, all groups of ketamine users showed evidence of unusual beliefs or mild 'delusions', with these being greatest in the frequent users and least in ex-users (i.e. it appeared dependent on the amount of the drug used). It is not clear to what extent this is a pre-existing difference in ketamine users, something that develops from using the drug or a mixture of both.

Says lead author Dr. Celia Morgan: "These findings have implications for the growing number of ketamine users in the UK as well as addiction professionals who may encounter increasing numbers of ketamine dependent users. These findings suggest these frequent ketamine users will be impaired, albeit transiently, in a variety of psychological domains."