| The objective of this study was to evaluate the long-term effect of ketamine use on both the cognition and psychological well-being of youths in Hong Kong.;Three hundred participants were recruited for the study, which lasted from December 2009 to December 2011. Participants were divided into three groups of 100 each: primarily ketamine (Primarily K) users, poly-drug ketamine (Poly K) users and healthy controls (HCs). Psychiatric assessments included screening with self-rating questionnaires and face-to-face interviews. All participants completed a detailed cognitive battery covering general intelligence, verbal memory, visual memory, executive function, motor speed and language.;The participants in the Primarily K group predominantly used ketamine, whereas those in the Poly K group used ketamine in addition to secondary drugs, of which cocaine and methamphetamine were the most frequent. Depressive disorder was the most common psychiatric disorder in both ketamine groups. Univariate analysis also showed the two ketamine groups to score poorly on most of the cognitive tests relative to the HC group. After adjusting for age, sex, education and Beck Depression Inventory (BDI) score, verbal and visual memory remained impaired in both ketamine groups in comparison with the HC group. Ketamine use in the past month was independently related to memory impairment in the Primarily K group. In subgroup analyses of Primarily K users, verbal and visual memory, motor speed, and some of the executive function indexes were significantly impaired in current users but not in ex-users. These findings suggest that the cognitive influence of ketamine is reversible. Moreover, the current ketamine users had a higher BDI score than the ex-users or HCs. However, the ex- and current poly-drug ketamine users exhibited a similar degree of memory impairment compared with the HCs. The female Primarily K users showed more visual memory impairment than their male counterparts, although females generally performed better than males in verbal memory.;In conclusion, the use of ketamine alone and in conjunction with other psychotropic drugs is associated with deficits in memory and executive function. The observed memory impairment was related primarily to recent ketamine use, with current Primarily K users presenting with a more severe memory deficit than current Poly K users. However, the Primarily K group realised improvement in cognitive impairment after abstaining from ketamine, whereas the Poly K group did not. In addition to cognitive functioning difficulties, more than half of the ketamine users suffered from depressive disorder. Moreover, the findings suggest that women may be more sensitive than men to visual memory impairment following chronic ketamine use. The findings of this study will be helpful in treating ketamine abuse, and reinforce the efficacy of abstinence from drugs. Further longitudinal research is needed to determine the reversibility of ketamine's effects and the mechanism by which that reversibility takes place. Further study is also needed to clarify the drug's sex-specific effects. |
