International self-controlled case series links peak self-harm risk to pre-treatment period in 460000 ADHD patients

Researchers pooled electronic health records from Hong Kong, New Zealand, South Korea, Taiwan and the UK covering 2001-2020. They applied a self-controlled case series design to compare self-harm incidence in the 90 days pre-treatment, first 90 days on medication, and later treatment periods against non-exposed intervals within the same individuals. Risk peaked before treatment start in every jurisdiction and remained elevated but lower once medication began, consistent with symptom severity rather than drug effect driving events. The study design eliminates time-invariant confounding and uses within-person comparisons, strengthening causal inference over prior observational reports. Absolute incidence rates were not published, yet the relative ordering was uniform despite differing prescribing cultures and data capture methods. Funding came from public research councils without industry involvement. Clinicians should intensify monitoring in the pre-treatment window when symptoms are worsening. The platform enables future analyses of discontinuation, restart, and socioeconomic modifiers. Next steps require prospective cohorts to test whether early intervention reduces the observed pre-treatment peak.