Background: The impact of attention-deficit/hyperactivity disorder (ADHD) and its pharmacotherapy on linear growth remains controversial. Prior studies report heterogeneous results and are limited by small sample sizes, incomplete developmental characterization, and difficulty separating disease and treatment effects.
Objective: To examine whether children with ADHD differ in linear growth across developmental stages and to assess the relative contribution of ADHD itself and pharmacologic treatment to observed growth differences, including potential dose-related effects.
Methods: We conducted a retrospective nationwide cohort study using population-based electronic health records from 2010 to 2024. Children aged 2–18 years with at least one recorded height measurement were included; conditions known to affect growth were excluded. ADHD was operationalized using clinically validated medication-based criteria (≥2 prescriptions). Outcomes were height-for-age z-score and short stature (z<−2 SD). Analyses included multivariable linear and logistic regression, mixed-effects dose–response modeling, and target-trial emulation using a doubly robust g-formula (AIPW) among children with ADHD.
Results: The final cohort comprised 2,058,226 children; 232,912 (11.3%) met criteria for ADHD, of whom 76% received pharmacotherapy. During early childhood, height-for-age z-scores did not differ by ADHD status. In prepubertal children, ADHD was associated with lower z-scores (β≈−0.061), and a similar but smaller association was observed during puberty (β≈−0.038). Postpubertally, the association was attenuated (β≈−0.011). The odds of short stature were higher in the prepubertal period (OR≈1.09) and remained modestly elevated during puberty, but not after puberty. In dose–response analyses of pharmacotherapy exposure, reductions in z-scores were observed only among children with high cumulative exposure (≥15 dispensations; β≈−0.047 for >20 dispensations); no association was observed with low-to-moderate exposure. In causal analyses restricted to children with ADHD, treatment initiation was associated with a small decrease in z-score (AIPW≈−0.026). Post-treatment z-scores and the prevalence of short stature did not differ between treated and untreated children.
Conclusions and Clinical Implications: Growth effects in ADHD are small, stage-specific, and possibly exposure-dependent, with no clinically meaningful difference in attained height or short-stature prevalence. These findings support targeted growth monitoring in higher-risk subgroups and proactive management of modifiable factors affecting growth (e.g., appetite, sleep), rather than broad changes to treatment strategies.
Keywords: ADHD; linear growth; short stature; methylphenidate; dose–response; target-trial emulation; AIPW.
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