Principal Investigator: Brooke Molina, PhD
Funding Source: National Institute of Mental Health
The Preschool Study was a 15-year study of the diagnostic criteria for Attention-Deficit/Hyperactivity Disorder (ADHD). Designed by original investigators Lahey and Pelham, the study began in 1995 with 140 four to six year olds in Pittsburgh, PA and another 120 four to six year olds in Chicago, IL. Approximately half of the children had been diagnosed with ADHD or were suspected of having the disorder.
The original purpose of the study was to determine if ADHD could be accurately diagnosed at an age when it is "normal" for children to be hyperactive, inattentive, and impulsive. We also wanted to see if the ADHD subtype diagnoses - Inattentive Subtype, Hyperactive-Impulsive Subtype, and Combined Subtype - are stable over time. In other words, would children continue to receive the same diagnosis year after year and would children who were originally diagnosed at this young age continue to meet diagnostic criteria for ADHD as they aged? As with our other longitudinal studies, this study also sought to learn more about the types of difficulties that are associated with ADHD and how they change as children become adolescents and approach adulthood.
Adolescents, along with their mothers, continued in the project until they reached the age of 18. More than 95% of eligible families continued to participate in annual assessments until the study ended in June of 2010.
The results of this study suggest that while many children improved over time, children who met diagnostic criteria for ADHD during the preschool years continued to exhibit more symptoms, experience greater difficulty, and engage in more risky behavior through childhood and adolescence than the children in the study who did not meet criteria for ADHD at ages 4-6. Thus, diagnosis of ADHD in early ages was found to have predictive validity as symptoms and impairment endured for most. It is important to note that while overall diagnosis of ADHD was stable, the subtype of ADHD assigned was highly variable across years of participation. More important, approximately 10% of youth diagnosed with ADHD in the preschool years were functioning as well as their peers not diagnosed with ADHD on multiple measures during their teen years. Higher numbers of inattention and hyperactivity-impulsivity symptoms measured in the preschool years predicted higher future level of these symptoms among the children with ADHD. Similarly, higher numbers of symptoms of oppositional, conduct disorder, anxiety and depression in preschool predicted higher levels of symptoms of these dimensions later. Additionally, higher levels of inattention, oppositional, conduct disorder, and anxiety symptoms predicted later impairment in functioning. Among children with ADHD, girls and children from families with lower family incomes experienced poorer outcomes. Finally, lower levels of hyperactivity-impulsivity symptoms at ages 4-6 predicted better functioning during adolescence.