Investigating the effects of age, IQ, dosing, and anthropometric measures on the treatment persistence in long-term methylphenidate use.

Objectives: This study aimed to determine anthropometric and clinical correlates of persistence to methylphenidate (MPH) treatment in Turkish youth with attention-deficit hyperactivity disorder (ADHD).

Methods: Data from medical records of 518 children and adolescents with ADHD were recorded between March 2012 and January 2022. Clinical variables of patients persistent to MPH ≥ 2 years were compared with those of the non-persistent group. Children and adolescent age groups were compared using Kaplan-Meier estimates for treatment drop-outs. Cox regression analysis until the treatment drop-out was implemented to calculate hazard ratios (HRs) for gender, age, full-scale IQ, and anthropometric measures. Weight, height, and body mass index (BMI) z-scores were calculated per national guidelines.

Results: Persistent and non-persistent study groups had similar full-scale IQ, weight, height, and BMI z-scores at treatment onset. The mean MPH dose was significantly higher in the persistent group compared to the non-persistent counterparts (31.43 ± 10.70 24.28 ± 9.60 mg/d,  < 0.001,  = 0.70). Compared to children, the adolescents showed earlier treatment drop-outs in males ( < 0.001) but not in females ( = 0.110). Younger age showed a positive effect on treatment persistence. Conversely, baseline BMI and IQ scores were not associated with long-term persistence.

Discussion: Our study demonstrated lower daily doses and older age-onset were associated with early drop-outs in MPH treatment. These findings supported the notion that effective dosing strategies at younger ages could increase the sustainability of the treatment with MPH in the Turkish population.