Impairment in Young Preschool Children with Symptoms of Attention-Deficit/Hyperactivity Disorder and Co-occurring Oppositional Defiant Disorder and Conduct Disorder

Background: We have limited knowledge of the impact of attention-deficit/hyperactivity disorder (ADHD) symptoms on the daily functioning of young preschool children. Objective: This study investigated the level of impairment related to symptoms of ADHD in different functional domains. It also addressed how impairment caused by ADHD was related to ADHD subtype, symptom load, gender, and the co-occurrence of oppositional defiant disorder, conduct disorder, or both. Method: Participating children (N = 807) who were 3.5 years old were recruited from a population-based sample included in The Norwegian Mother and Child Cohort Study. Children who scored above the 90th percentile for ADHD symptoms were included in the present sample. The assessment of the symptoms and functional impairment described in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, text revision, was based on parental ratings and the semi-structured psychiatric interview entitled “The Preschool Age Psychiatric Assessment.” Results: Added burden and discord within family relationships were the areas that were most severely affected. All domain scores were strongly intercorrelated, and they were added to each child’s total score. Children with symptoms of ADHD, inattentive type (mean [M], 3.5; standard deviation [SD], 3.4), or ADHD, hyperactive/impulsive type (M, 2.9; SD, 2.7), were significantly less impaired than children with symptoms of ADHD, combined type (M = 6.4; SD = 3.8; p < .001). Furthermore, co-occurring oppositional defiant disorder was associated with higher impairment scores (M, 6.1; SD, 4.3) than ADHD alone (M, 3.2; SD, 2.9; p < .001. About 30% of the variance of impairment score of ADHD was explained by symptoms of ADHD and co-occurring symptoms of oppositional defiant disorder and conduct disorder. Few gender differences were observed. Conclusion: Overall, these non-referred young children with clinical symptoms of ADHD were only modestly impaired. Impairment related to ADHD occurred mainly in the areas of family functioning, and it was associated with ADHD subtype and comorbidity. Still, it is important to assess the impact of ADHD symptoms and coexisting difficulties among preschoolers to identify children and families who are in need of early intervention efforts