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Background and Objective: Evidence and clinical guidelines on methylphenidate dosing in different weight status groups are limited. This study aimed to evaluate real-world methylphenidate dosing practices and treatment discontinuation rates in children and adolescents in relation to weight status.

Method: We used data from the BMI Epidemiology Study Gothenburg cohort, which includes weight and height measurements linked to national registers. Exposures included body weight, standardised body mass index (zBMI), and body mass index (BMI) status. The main outcome was the dose and weight-adjusted dose of methylphenidate for the baseline and follow-up prescriptions. We used a logistic regression model to evaluate treatment discontinuation in relation to weight status, sex, and age.

Results: The study included 1741 children and adolescents who initiated methylphenidate treatment and had BMI available. Among them, 612 had a follow-up prescription with BMI available. Children and adolescents with overweight and obesity received slightly higher absolute doses of methylphenidate at baseline prescriptions, but lower weight-adjusted doses. Children and adolescents with underweight received higher weight-adjusted doses. Absolute dose increases between treatment initiation and follow-up were highest in children and adolescents with obesity and lowest in children and adolescents with underweight. Girls received higher absolute and weight-adjusted doses than boys at follow-up, while children over 12 years of age received higher absolute but lower weight-adjusted doses than children under 12 years. A significantly higher proportion of children and adolescents with baseline underweight discontinued treatment during the first year, compared with the normal weight group. Beside lower baseline zBMI, female sex and higher age were also significantly associated with treatment discontinuation during the first year.

Conclusion: Our findings suggest that weight status, sex, and age are significantly associated with differential methylphenidate dosing and treatment discontinuation in children and adolescents.