Earlier treatment of attention-deficit/hyperactivity disorder (ADHD) with stimulant drugs may reduce the risk of academic decline, especially in mathematics, a new study suggests. Risk reduction differs for girls and boys.
To explore whether starting stimulant medication for ADHD later impairs academic progress in mathematics and language arts in 9- to 12-year-old children, the population-based study examined data on 11,872 Icelandic children born between 1994 and 1996. The children took mandatory standardized tests in fourth grade and seventh grade. Researchers correlated nationwide data from the Icelandic Medicines Registry and the Database of National Scholastic Examinations.
They divided the 1,029 medicated children into 3 groups according to how long after taking the fourth-grade test they began treatment: within 12 months, 13 to 24 months, or 25 to 36 months. The 25- to 36-month group was considered to have received late treatment. Most children received extended-release methylphenidate.
Average academic performance in nonmedicated children did not change significantly between the fourth-grade and seventh-grade tests, but mean performance declined in the medicated children, especially the ones who started treatment between 25 and 36 months after their fourth-grade test. The late-treated children showed a crude probability of academic decline—defined as a drop of 5 or more percentile points—of 72.9% (mean decline 9.4 points) in mathematics and 42.9% (mean decline 3.4 points) in language arts.
Compared with children who started medication within 12 months of the fourth-grade test, late starters had a multivariable adjusted risk ratio for performance decline of 1.7 in mathematics and 1.1 in language arts. The absolute increase in risk for late-treated children was 32% in mathematics but only 4% in language arts.
The absolute risk of academic decline in mathematics and the adjusted risk ratio were higher for girls (86.7% and 3.6, respectively) than for boys (66.7% and 1.4, respectively). Researchers note that girls demonstrated a clear risk reduction only in mathematics, whereas boys showed marginal reductions in both mathematics and language arts.
The researchers suggest that stimulant drug treatment for children with ADHD has a more positive effect on the brain’s cognitive function that controls mathematical ability than on the function that controls language ability.
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