First-time offenders for recreational ketamine use under a new penalty system in Taiwan: Incidence, recidivism and mortality in national cohorts from 2009 to 2017

[[abstract]]BACKGROUND AND AIMS: Ketamine has become a new recreational drug of choice among young people in parts of Asia. Using national databases in Taiwan, this study aimed to 1) examine the yearly trend in the ketamine offence rate over time; 2) estimate the 3-year risk of drug-related reoffence and its correlates among the first-time offenders; and 3) estimate the 3-year standardized mortality ratio (SMR) among the first-time offenders. DESIGNS: Retrospective cohort studies of offenders for recreational ketamine use in a penalty system initiated in 2009. SETTINGS AND PARTICIPANTS: Offenders for recreational ketamine use were identified from the Administrative Penalty System for Schedule III/IV Substances database from 2009 to 2017, and the reoffence rate and mortality among first-time offenders were assessed via record-linkage within the database as well as with both the criminal drug offence database and the national mortality database. The cohort from 2009 to 2016 (n = 39,178) was used for the recidivism analysis, and the cohort from 2009 to 2013 (n = 25,357) was used for the 3-year SMR analysis. MEASUREMENTS: Recidivism was estimated using survival analysis of the event as re-arrest for using ketamine, more serious illicit drugs (Schedule I/II), or any illicit drugs (ketamine or Schedule I/II). SMRs were estimated for overall and cause-specific death within 3 years after the first offence for ketamine use. FINDINGS: The age-standardized rates for both prevalent (0.14%) and first-time offenders (0.07%) peaked in 2013 and then decreased steadily. The 3-year risk of reoffence was 33.85% (95% CI: 33.23-34.47%) for ketamine use and 39.52% (39.00-40.04%) for any illicit drug use. These first-time offenders had an SMR of 4.9 (4.3-5.4) for overall mortality, 2.1 (1.6-2.7) for natural deaths, and 7.6 (6.7-8.6) for unnatural deaths. CONCLUSIONS: Recreational ketamine use in Taiwan appears to lead not only to high risk for drug-related reoffence but also to excess mortality