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Validity of ADHD Symptoms in Toddlers

Attention deficit/hyperactivity disorder (ADHD) is one of the most common child neurodevelopmental disorders. The disorder is typically diagnosed in elementary school, but there is growing evidence for the validity of ADHD in preschoolers, and symptoms likely emerge even earlier than preschool years. Research suggests that ADHD symptoms can be evident in toddlers beyond developmentally appropriate behavior, and symptoms in toddlers are predictive of later impairment. However, few studies have examined the validity of Diagnostic and Statistical Manual of Mental Disorders (DSM) ADHD symptoms in this younger population. The present study examined the 18 DSM ADHD symptoms in a community sample of 2-year-old children by recruiting parents (N = 321) online through Amazon’s Mechanical Turk. Results showed that ADHD symptoms were fairly common in 2-year-old children; a substantial minority (22%) of children met symptom criteria for ADHD. ADHD showed similar construct validity and symptom utility to older children, with the exception of verbal hyperactive-impulsive symptoms. Similar to school-age children, a two-factor model of ADHD, was the best fit. ADHD symptoms showed convergent and divergent validity with a temperament questionnaire; symptoms were related to similar traits such as motor activation and inhibitory control, and not related to traits such as cuddliness or fear. Finally, item response theory analyses showed that items besides verbal symptoms discriminated well between toddlers high and low on ADHD. Results suggest that ADHD symptoms, with the exception of verbal symptoms, demonstrate good validity in 2-year-old children, and provide support for conducting prospective studies to determine whether 2-year-old children showing high levels of ADHD symptoms are at high risk for the development of ADHD.