The impact of ADHD and neurostimulant treatment on normalized height deviance after accounting for genetic height potential

BACKGROUND: Studies have reported conflicting findings regarding whether attention-deficit/hyperactivity disorder (ADHD) and neurostimulant (NS) treatment influence growth. The study aimed to evaluate the impact of ADHD and NS-treatment on adult height (AH), while accounting for individual expected height. METHODS: Retrospective controlled cohort study using a nationwide healthcare provider database. Children born 1995-2003 were classified into: (1) untreated ADHD, (2) NS-treated ADHD, and (3) controls, followed until AH (girls ≥17 years, boys ≥19 years). Observed height index (OHI) = individual AH ÷ sex-specific mean AH of controls. Expected height index (EHI) = individual's MPH ÷ sex-specific mean MPH of controls. Normalized height deviance (NHD) = OHI - EHI. ADHD impact = mean NHD(untreated ADHD) - mean NHD(controls). NS-treatment impact = mean NHD(NS-treated) - mean NHD(untreated ADHD). Significance was set at p ≤ 0.05. Effect sizes reported as Cohen's d and f. RESULTS: The cohort included 17,517 children with ADHD (5671 untreated; 11,846 NS-treated) and 47,258 controls. Girls' ADHD impact was -0.28% (p < 0.001; Cohen's d = 0.08), and in boys -0.11% (p = 0.12; Cohen's d = 0.03). Girls' NS-treatment impact was -0.26% (p = 0.005, Cohen's d = 0.07), in boys -0.10% (p = 0.25). CONCLUSIONS: ADHD and NS-treatment were associated with negligible effect sizes in girls and non-significant differences in boys. IMPACT: After accounting for individual familial genetic height potential, ADHD and neurostimulant treatment are associated with statistically detectable but clinically negligible differences in adult height. Introduces normalized height deviance (NHD), a genetics-adjusted measure that distinguishes true growth effects from delayed maturation. Uses a large, nationwide cohort followed to adult height, resolving long-standing inconsistencies in prior growth studies. Provides reassurance that ADHD and neurostimulant treatment do not meaningfully impair final adult stature and supports informed clinical decision-making.