Multiplex and Sporadic ADHD

As the prevalence of ADHD continues to increase world-wide, there is increased scientific interest in understanding the etiology, risk factors, course, and predictors of treatment response. However, increased awareness of ADHD and expanding diagnostic criteria contribute to diagnostic heterogeneity, increasing the need for “restricted phenotypes” in ADHD research. Will review the ADHD diagnostic process and describe the example of Resistance to Thyroid Hormone as a phenocopy of ADHD. Familiality of ADHD (i.e., Multiplex families) and stimulant response are reliable phenotypes that all clinicians working with ADHD are aware of. In moving toward precision medicine, a strategy comparing multiplex versus sporadic cases has been fruitful for other neurodevelopmental disorders, such as Autism Spectrum Disorders, and show promise in ADHD. Will discuss how a similar strategy might apply to ADHD and then describe a hierarchical model for subtyping clinical samples based on presumed etiology.