This study examines the prevalence of non-suicidal self-injury (NSSI) and deliberate self-harm (DSH) among adolescents globally, using empirical data from 52 studies published between 2005 and 2011. The results show that the mean lifetime prevalence of NSSI is 18.0% (SD = 7.3), and DSH is 16.1% (SD = 11.6), with no statistically significant difference between the two. Single-item assessments tend to yield lower prevalence rates compared to specific behavior checklists. The study also finds that prevalence rates have stabilized over the past five years, suggesting a stabilization in the rates of NSSI and DSH. The findings highlight the need for a standardized assessment approach to facilitate cross-cultural comparisons and improve the understanding of these behaviors. The study concludes that NSSI and DSH have comparable prevalence rates across different countries and cultures, supporting the cultural validity of the DSM-5's proposed diagnosis of non-suicidal self-injury disorder.This study examines the prevalence of non-suicidal self-injury (NSSI) and deliberate self-harm (DSH) among adolescents globally, using empirical data from 52 studies published between 2005 and 2011. The results show that the mean lifetime prevalence of NSSI is 18.0% (SD = 7.3), and DSH is 16.1% (SD = 11.6), with no statistically significant difference between the two. Single-item assessments tend to yield lower prevalence rates compared to specific behavior checklists. The study also finds that prevalence rates have stabilized over the past five years, suggesting a stabilization in the rates of NSSI and DSH. The findings highlight the need for a standardized assessment approach to facilitate cross-cultural comparisons and improve the understanding of these behaviors. The study concludes that NSSI and DSH have comparable prevalence rates across different countries and cultures, supporting the cultural validity of the DSM-5's proposed diagnosis of non-suicidal self-injury disorder.