Regulatory reform and adult methylphenidate dispensing in France: a nationwide interrupted time-series study.

BACKGROUND: France reports markedly lower adult attention-deficit/hyperactivity disorder (ADHD) medication use than other high-income countries despite similar prevalence. Methylphenidate is the predominant ADHD medication dispensed in France, accounting for the large majority of stimulant prescriptions in adults. Until recently, methylphenidate initiation was restricted to hospital specialists and largely excluded adult indications. Regulatory changes between 2021 and 2023 expanded adult access. OBJECTIVE: Examine national trends in adult methylphenidate dispensing in France and quantify the impact of the November 2021 regulatory reform. METHODS: Nationwide retrospective cohort study using the French National Health Data System (SNDS), including adults (≥18 years) with at least one community pharmacy dispensation of methylphenidate between January 2015 and December 2024. Weekly population-standardised dispensing rates were analysed using interrupted time-series models (quasi-Poisson) to estimate level and trend changes, stratified by sex and prescriber specialty. A secondary analysis examined incident treatment initiation to distinguish new users from individuals continuing pre-existing therapy. FINDINGS: Between 2015 and 2024, a total of 195 393 adults received methylphenidate. Before the reform, weekly dispensing grew gradually (~0.2% per week). At reform implementation, an immediate 10.9% level increase occurred, followed by a sustained acceleration (~0.7% per week), largely driven by new treatment initiations. Similar patterns were seen in both sexes, though the immediate increase was greater for dispensing attributed to psychiatrists. CONCLUSIONS: The November 2021 reform was associated with a rapid and sustained expansion of adult methylphenidate use over the 3 years following the reform, primarily through increased treatment initiation, suggesting that prior regulatory constraints largely explained historically low treatment rates. Longer follow-up will be needed to assess whether this trajectory is maintained. CLINICAL IMPLICATIONS: Regulatory changes expanding ADHD treatment access may produce rapid prescribing increases, requiring adequate specialist capacity and stimulant use monitoring.