A population-based study of stimulant drug treatment of ADHD and academic progress in children.
OBJECTIVE
We evaluated the hypothesis that later start of stimulant treatment of attention-deficit/hyperactivity disorder adversely affects academic progress in mathematics and language arts among 9- to 12-year-old children.


METHODS
We linked nationwide data from the Icelandic Medicines Registry and the Database of National Scholastic Examinations. The study population comprised 11,872 children born in 1994-1996 who took standardized tests in both fourth and seventh grade. We estimated the probability of academic decline (drop of ≥ 5.0 percentile points) according to drug exposure and timing of treatment start between examinations. To limit confounding by indication, we concentrated on children who started treatment either early or later, but at some point between fourth-grade and seventh-grade standardized tests.


RESULTS
In contrast with nonmedicated children, children starting stimulant treatment between their fourth- and seventh-grade tests were more likely to decline in test performance. The crude probability of academic decline was 72.9% in mathematics and 42.9% in language arts for children with a treatment start 25 to 36 months after the fourth-grade test. Compared with those starting treatment earlier (≤ 12 months after tests), the multivariable adjusted risk ratio (RR) for decline was 1.7 (95% confidence interval [CI]: 1.2-2.4) in mathematics and 1.1 (95% CI: 0.7-1.8) in language arts. The adjusted RR of mathematics decline with later treatment was higher among girls (RR, 2.7; 95% CI: 1.2-6.0) than boys (RR, 1.4; 95% CI: 0.9-2.0).


CONCLUSIONS
Later start of stimulant drug treatment of attention-deficit/hyperactivity disorder is associated with academic decline in mathematics.
Center of Public Health Sciences, Faculty of Pharmaceutical Sciences, School of Health Sciences, University of Iceland, Reykjavik, Iceland. helga.zoega@mssm.edu
Helga
H
Zoëga
Kenneth J
KJ
Rothman
Krista F
KF
Huybrechts
Örn
Ö
Ólafsson
Gísli
G
Baldursson
Anna B
AB
Almarsdóttir
Sólveig
S
Jónsdóttir
Matthías
M
Halldórsson
Sonia
S
Hernández-Diaz
Unnur A
UA
Valdimarsdóttir
D000124:Achievement; D000367:Age Factors; D000661:Amphetamine / Q000008:administration & dosage* / Q000627:therapeutic use; D000069445:Atomoxetine Hydrochloride; D001289:Attention Deficit Disorder with Hyperactivity / Q000188:drug therapy* / Q000523:psychology; D000697:Central Nervous System Stimulants / Q000008:administration & dosage* / Q000627:therapeutic use; D002648:Child; D004521:Educational Measurement; D005260:Female; D006801:Humans; D007055:Iceland; D007803:Language Arts; D008297:Male; D008433:Mathematics; D008774:Methylphenidate / Q000008:administration & dosage* / Q000627:therapeutic use; D015999:Multivariate Analysis; D016017:Odds Ratio; D011437:Propylamines / Q000008:administration & dosage* / Q000627:therapeutic use; D012042:Registries; D012737:Sex Factors; D016896:Treatment Outcome
D000697:Central Nervous System Stimulants; D011437:Propylamines; D008774:Methylphenidate; D000069445:Atomoxetine Hydrochloride; D000661:Amphetamine