Relationship between cognitive impairment and depressive symptoms in current ketamine users

Both cognitive impairment and depressive symptoms have been reported in ketamine users. However, no previous study has examined the relationship between them. This study aimed to examine cognitive functions and depressive symptoms and their relationship in young ketamine users in Hong Kong.

Fifty-one current ketamine users, 49 ex-ketamine users, and 100 healthy controls were recruited from counseling and youth centers in Hong Kong in this cross-sectional study. Cognitive assessment included mental and motor speed; working, verbal, and visual memory; and executive functions. Depressive symptoms were measured using the Beck Depression Inventory. One-way analyses of covariance (ANCOVA) and chi-square tests were used to analyze participants' demographic data, patterns of drug use, Beck Depression Inventory score, and performance in a cognitive battery. Cognitive functions were adjusted for age, gender, and education using ANCOVA. Correlations between the Beck Depression Inventory score and cognitive functions were examined using Pearson's correlation coefficient.

Cognitive impairment was found only in current ketamine users in the domains of mental and motor speed (p < .001), visual and verbal memory (p < .001), and executive functions (p < .001). Depressive symptoms were also more frequently found in current ketamine users (p < .001). Correlations between depressive symptoms and certain cognitive scores were statistically significant but modest.

Current ketamine use is associated with cognitive impairment. Illicit substance treatment and rehabilitation services should pay attention to ketamine's cognitive effects and motivate their clients to quit using ketamine and stay abstinent.