Development of a checklist of short-term and long-term psychological symptoms associated with ketamine use.

Background: Ketamine is an increasingly popular drug of abuse in China but there is currently no method for classifying the psychological effects of ketamine in individuals with ketamine dependence.

Aim: Develop a scale that characterizes the acute and long-term psychological effects of ketamine use among persons with ketamine dependence.

Methods: We developed a preliminary symptom checklist with 35 dichotomous ('yes' or 'no') items about subjective feelings immediately after ketamine use and about perceived long-term effects of ketamine use that was administered to 187 inpatients with ketamine dependence recruited from two large hospitals in Guangzhou, China. Exploratory factor analysis (EFA) was conducted on a randomly selected half of thesample to reduce the items and to identify underlying constructs. Confirmatory factor analysis (CFA) was conducted on the second half of the sample to assess the robustness of the identified factor structure.

Results: Among the 35 symptoms, the most-reported acute effects were 'floating or circling' (94%), 'euphoric when listening to rousing music' (86%), and 'feeling excited, talkative, and full of energy' (67%). The mostreported long-term symptoms were 'memory impairment' (93%), 'personality changes' (86%), and 'slowed reactions' (81%). EFA resulted in a final 22-item scale best modelled by a four-factor model: two factors representing chronic symptoms (social withdrawal and sleep disturbances), one about acute psychoticlike symptoms, and one that combined acute drug-related euphoria and longer-term decreased libido. CFA showed that these 4 factors accounted for 50% of the total variance of the final 22-item scale and that the model fit was fair (Goodness of Fit Index, GIF=83.3%; Root Mean Square Error of Approximation, RMSEA=0.072).

Conclusion: A four-factor model including social withdrawal, sleep disturbance, psychotic-like symptoms, and euphoria at the time of drug use provides a fair description of the short-term and long-term psychological symptoms associated with ketamine use. Future work on the 22-item version of the scale with larger samples is needed to confirm the validity of this 4-factor structure, to assess the scale's test-retest reliability, and to determine whether or not it can be useful in the differential diagnosis and monitoring of treatment of individuals with ketamine dependence.