OBJECTIVE: We sought to evaluate changes in the prevalence of self-harm coding among children and adolescents following the transition from International Classification of Diseases, 9(th) revision, clinical modification (ICD9-CM) to International Classification of Diseases, 10(th) revision, clinical modification (ICD10-CM).
METHODS: We performed interrupted time series (ITS) analyses on monthly rates of medically attended deliberate self-harm in the 15 months prior to and 15 months following the transition to ICD10 in October 2015 across nine health systems. Separate models were estimated for youths aged 6-11 years and youths aged 12-17 years. Segmented regression models with autocorrelation terms were used to estimate discontinuities and changes in trends pre- and post-October 2015.
RESULTS: There was a 0.18 per 100,000 youths per month (slope change) in the 6-11 age group. There was an immediate 38.5 per 100,000 youths change in medically attended deliberate self-harm and a sustained 6.5 per 100,000 per month (slope) change in the 12-17 age group.
CONCLUSIONS: The transition to ICD10 was associated with significant changes in monthly rates of medically attended deliberate self-harm in children and adolescents. These results present challenges for interpreting long-term trends in medically attended deliberate self-harm rates and evaluating the effects of contemporaneous efforts to reduce self-harm.