Updated June 08, 2015.

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

The Preschoolers with Attention-Deficit/Hyperactivity Disorder Treatment Study (PATS) is a National Institute of Mental Health-sponsored, multisite study involving more than 300 preschoolers with ADHD. It was the first long-term, large scale study designed to determine the safety and effectiveness of treating preschoolers who have ADHD with methylphenidate (Ritalin).

Results of this study found that, overall, low doses of methylphenidate over the short term are effective and safe, provided the preschoolers — who are particularly susceptible to side effects — are closely monitored.

Read more about PATS

The Preschool ADHD Treatment Follow-Up Study

A total of 207 participants (75% male) from the original PATS participated in the follow-up study, the Preschool ADHD Treatment Follow-Up Study (PATS F/U). Investigators examined the longitudinal changes in symptom severity and ADHD diagnosis during a 6-year period. This study provided a unique opportunity to examine the course of ADHD in children who were first diagnosed in the preschool years (ages 3-5 years) with moderate-to-severe symptoms at original diagnosis.

The information we have about the course of moderate-to-severe ADHD in children diagnosed at very young ages is limited. As more preschool age kids with ADHD are identified and treated, it becomes even more important to understand the long-term trajectory of ADHD in these children. Getting a better handle on the course of ADHD in this age group is vital for establishing optimal interventions early on for these children and their families.

Study Method

Families of the 304 participants enrolled in the original PATS were contacted by phone or mail and invited to return for an observational follow-up.

Of these families, 207 children took part in the PATS F/U, which was conducted at the following sites: Columbia University, Duke University Medical Center, Johns Hopkins University, New York University, University of California-Irvine, and University of California-Los Angeles.

The assessment process that was used in the original PATS was repeated in the PATS F/U. Children were evaluated in three follow-up assessment visits: at year 3 follow up (mean age of the children was 7.4 years), at year 4 follow up (mean age of the children was 8.3 years), and at year 6 (mean age of children was 10.4 years). The assessments involved parents and teachers rating symptom severity. An M.D. or Ph.D. clinician/researcher performed a comprehensive clinical evaluation with the caregiver and the child to determine current psychiatric diagnosis at the 3-year and 6-year follow up visit.

Of the 207 children enrolled, 206 participated in assessment at year 3; 189 participated in assessment at year 4; and 186 took part in assessment at year 6.

Study Results

Approximately 90% of the children in the study continued to be diagnosed with ADHD into mid-to-late childhood. Though there was an initial decline in some of the symptoms, for the most part severity of symptoms in the children remained primarily in the moderate-to-severe range, despite use of medications. Having a co-occurring diagnosis of oppositional defiant disorder (ODD) or conduct disorder (CD) during follow-up was the strongest predictor of diagnostic stability.

Girls and boys exhibited different changes in the course of their ADHD over the 6-year period. At baseline, the girls with ADHD tended to have more severe symptoms (especially inattentiveness). Although they showed a greater decline in symptom severity over time compared to boys, the girls' symptoms remained more severe than boys throughout the study period, with the exception of hyperactivity and impulsivity in classroom settings.

Study Conclusions

ADHD in preschoolers is a relatively stable diagnosis over a 6-year period. The course is generally chronic, with high symptom severity and impairment in very young children with moderate-to-severe ADHD, despite treatment with medication. Development of more effective ADHD intervention strategies is needed for this age group.

Interestingly, in the original PATS, there was a positive effect in completion of the medication maintenance phase as symptoms of inattention and hyperactivity/impulsivity declined. Investigators did not see an independent effect of medication (on versus off during follow-up) on the teacher and parent ratings of ADHD severity in the PATS F/U. It is important to note that treatment was not controlled during the majority of the 6-year follow-up period as it was during the original PATS.

"These findings raise questions that unfortunately cannot be answered from these data," the study authors write. "For example, why were the medications, as administered in the community, not sufficiently effective in reducing symptoms to below clinical ranges in most participants? Was adherence a problem? Alternatively, it is possible that pharmacotherapy practices of community practitioners were not geared to maximize clinical benefit."

"Our study was not designed to answer these questions, but whatever the reason may be, it is worrisome that children with ADHD, even when treated with medication, continue to experience symptoms, and what we need to find out is why that is and how we can do better," says lead investigator Mark Riddle, M.D., a pediatric psychiatrist at Johns Hopkins Children's Center. "ADHD is becoming a more common diagnosis in early childhood, so understanding how the disorder progresses in this age group is critical. We found that ADHD in preschoolers is a chronic and rather persistent condition, one that requires better long-term behavioral and pharmacological treatments than we currently have."

Knowing that ADHD diagnosis in the preschool years tends to persist throughout childhood, the NIMH stresses that further research efforts should focus on early, intensive interventions that include medications, behavioral interventions and parent training.

The study was published online February 11, 2012 in the Journal of the American Academy of Child and Adolescent Psychiatry.

Additional Reading:
6 Things You Need to Know If Your Child Has With ADHD

<sub>Source:

Mark A.Riddle, M.D., KseniyaYershova, Ph.D., DeborahLazzaretto, M.S., NatalyaPaykina, M.A., Gayane Yenokyan, Ph.D., LaurenceGreenhill, M.D., HowardAbikoff, Ph.D., BenedettoVitiello, M.D., TimWigal, Ph.D., JamesT.McCracken, M.D., ScottH.Kollins, Ph.D., DesireeW.Murray, Ph.D., Sharon Wigal, Ph.D., ElizabethKastelic, M.D., JamesJ.McGough, M.D., SusandosReis, Ph.D., Audrey Bauzo´ -Rosario, M.A., AnnamarieStehli, M.P.H., KellyPosner, Ph.D.; The PreschoolAttention-Deficit/HyperactivityDisorder Treatment Study(PATS)6-YearFollow-Up, Journal of the American Academy of Child & Adolescent Psychiatry, published online February 11, 2013.

National Institute of Mental Health, Long-term Course of ADHD Diagnosed in Preschool Years Can Be Chronic and Severe, February 12, 2013.</sub>