- There are many trends in the diagnosis and treatment of attention deficit hyperactivity disorder (ADHD) that have emerged over the past several years. The first of these emerging trends is the growing prevalence of ADHD diagnoses across age groups and cultures. Although the causes of this growing prevalence are unclear, several suggestions, including a broader definition of ADHD, are discussed as potential contributions. A second emerging issue is related to the underlying theory of ADHD. Barkley's biopsychosocial model of ADHD is briefly discussed as a prototype model to help in the understanding of ADHD. Finally, the growing trend in pharmacological treatment of ADHD is discussed. Stimulant medications, as well as a recent nonstimulant medication are discussed and compared with nonpharmacological alternatives.