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Long-term Course of ADHD Diagnosed in Preschool Years Can be Chronic and Severe

Science Update

Attention deficit hyperactivity disorder (ADHD) that is first diagnosed in the preschool years tends to be chronic and severe, but each child’s course of illness is different, according to long-term follow-up data from the NIMH-funded Preschool ADHD Treatment Study (PATS). The study was published online February 11, 2013, in the Journal of the American Academy of Child and Adolescent Psychiatry.


preschool-aged boy
Source: iStock Photo

Most ADHD studies focus on school-aged children, especially boys. PATS was the first long-term, large-scale study designed to focus on preschoolers with ADHD, and to determine the safety and effectiveness of treating them with methylphenidate (Ritalin). Results of the initial study found that overall, low doses of this medication over the short term are effective and safe, provided the preschoolers, who are particularly susceptible to side effects, are closely monitored.

In this follow-up study, the original participants—ages 3–5 at the time—were followed for six years after PATS began to track the clinical course of their ADHD. Parents and teachers were asked about the child’s symptoms three, four and six years after the end of the study.

Results of the Study

Of the original 304 participants, 68 percent participated in the follow-up study. After six years, 89 percent of participants still met criteria for ADHD. Although some symptoms had decreased, many of them still exhibited severe symptoms, despite use of medications. Overall, the children’s illness trajectories varied considerably.

Girls and boys also showed different changes in the course of their illness. At baseline, girls tended to have more severe symptoms, especially inattentiveness. Although they showed a steeper decline in symptom severity over time compared to boys, their symptoms remained more severe than boys throughout the study period, with the exception of hyperactivity and impulsivity in classroom settings.


As more preschoolers are diagnosed with ADHD and getting treated for it, knowing the long-term course of the disorder is important for establishing the most effective interventions early in the course of the illness. And because ADHD diagnosis in the preschool years tends to persist throughout childhood, early, intensive interventions that include medications, behavioral interventions and parent training are needed.

What’s Next

In an effort to improve outcomes for these children, more research is needed on the effects of ADHD medications on preschoolers over the long term, as well as the effects of combining different medications. In addition, more research is required to identify individual characteristics that could increase a child’s risk of long-term ADHD as well as those characteristics of children whose symptoms subside as they age.


Riddle M et al. The Preschool ADHD Treatment Study (PATS) 6-Year Follow-up . Journal of the American Academy of Child and Adolescent Psychiatry, published online February 11, 2013.