Building the Evidence to Treat Preschoolers With ADHD in Real-Life Settings.

Abundant evidence indicates that attention-deficit/hyperactivity disorder (ADHD) has its roots in the early stages of development. Genetic risk plays a major influence and interacts with a variety of environmental exposures in complex dynamic ways, leading to heterogeneous neurobiological processes that eventually emerge clinically.1 The heterogeneity of etiological mechanisms is reflected by a heterogeneous clinical constellation and trajectories of symptoms and associated disorders. One common developmental trajectory of ADHD is the onset during the preschool age, with stability of approximately 90% to school age in clinical samples.2 .