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Objective: To estimate the adherence of children and adults to oral stimulant ADHD treatments in Sweden during the period 2015 to 2020.

Methods: This retrospective, nationwide, register-based study evaluated all patients who were dispensed oral formulation stimulants (Anatomical Therapeutic Chemical [ATC] codes: N06BA01, N06BA02, N06BA04, N06BA12) identified in the Swedish Prescribed Drug Register. Treatment episodes were constructed based on drug dispensation data, and treatment adherence was calculated for each treatment episode using a Proportion of Days Covered approach with a modified one-pill-a-day method.

Results: Between 2015 and 2020, 158,413 treatment episodes were recorded in 128,366 patients, corresponding to a median 1.23 treatment episodes per patient. The majority of treatment episodes involved methylphenidate (64.0%), followed by lisdexamfetamine (32.2%), dexamfetamine (3.0%), and amphetamine (0.8%). Overall treatment adherence was high (78.2%), and was similar for patients receiving methylphenidate, lisdexamfetamine, and dexamfetamine. The proportion of patients with ≥80% medication adherence was high (69.3%–71.8%) for adults aged ≥25 years, but was low for adolescents aged 12 to 17 years (49.7%–52.4%).

Conclusions: The overall rates of treatment adherence are high for children and adults receiving ADHD medication in Sweden. We observed lower adherence among adolescents, which warrants further study.