At what age might I begin to worry about whether my child has ADHD? Can ADHD be diagnosed in a preschooler?

ADHD can be diagnosed in a child as young as 3 years of age. Signs of ADHD in preschoolers may include a noticeably high activity level, inability to persist with tasks, problems in following group instructions, poor behavior modulation, difficulties with social interactions, unending curiosity, excessive aggression or destructive play, silliness, bossiness, and impulsivity. Preschoolers with ADHD may have sleep problems, such as restless or decreased sleep. In addition, argumentative behavior and temper tantrums may be more common in preschoolers with ADHD. These children may also be quite immature, frequently demonstrating off-task or inappropriate behaviors. All of this can contribute to conflicts within the family, ranging from battles with siblings and parents to difficulties in keeping baby-sitters.