Overview

• The study used target trial emulation on Swedish national register data from 2007–2020 to compare patients who began medication within three months of an ADHD diagnosis with those who did not.
• Early initiators showed adjusted incidence rate ratios of 0.83 for suicidal behaviours, 0.85 for substance misuse, 0.88 for transport accidents and 0.87 for criminality over two years.
• Individuals with recurrent events and subgroups such as adults over 25 and women experienced larger reductions, with substance misuse and criminality rates dropping by about 25% among repeat cases.
• Stimulant treatments, mainly methylphenidate, were associated with greater reductions in harmful outcomes than non-stimulants, and sensitivity analyses confirmed consistency when extending the initiation window and accounting for drug switches.
• As an observational study, it cannot prove causation; authors noted limitations in adherence tracking, dosage information and applicability beyond Sweden and emphasized the findings’ role in guiding clinical practice and policy discussions.