The study split the participants into five groups: daily users, recreational users who took the drug once or twice a month, former users, users of other drugs, and people who did not use any drugs. All participants underwent a series of memory tests, completed questionnaires, and had a 1-year followup.

The group of daily users performed significantly worse on memory tests, with their performance worsening over the year. There was no significant difference between the other groups.

All groups of ketamine users held "unusual beliefs or mild delusions, such as conspiracy theories" according to the psychological questionnaires.