brain sciences Review Attention-Deficit/Hyperactivity Disorder Predominantly Inattentive Subtype/Presentation: Research Progress and Translational Studies Ike C. de la Peña 1,* , Michael C. Pan 2,3, Chau Giang Thai 1 and Tamara Alisso 1 1 Department of Pharmaceutical and Administrative Sciences, Loma Linda University School of Pharmacy, Loma Linda, CA 92350, USA;
[email protected] (C.G.T.);
[email protected] (T.A.) 2 Department of Psychology, Korea University, Seoul 02841, Korea;
[email protected] 3 Division of Social Sciences, University of the Philippines Visayas Tacloban College, Tacloban 6500, Philippines * Correspondence:
[email protected]; Tel.: +1-909-651-5995; Fax: +1-909-558-0446 Received: 23 April 2020; Accepted: 9 May 2020; Published: 14 May 2020 Abstract: Research on the predominantly inattentive attention-deficit/hyperactivity disorder (ADHD-PI) subtype/presentation is important given its high prevalence, but paradoxically it is under-recognized and undertreated. The temporal stability of the inattention symptom could impact the high worldwide prevalence of ADHD-PI. Some evidence suggests differences in the nature of attentional deficit in ADHD-PI vs. that in other subtypes. Impairments in neuropsychological, neurocognitive, and social functioning are also evident in ADHD-PI, which could be specific to the subtype (e.g., processing speed, social perception, and skills), or differ from others in severity. Neuroimaging studies have also revealed ADHD-PI-specific neuropathological abnormalities and those that are shared with other subtypes. ADHD-PI is highly comorbid with learning and internalizing (e.g., anxiety and depression) disorders. There is no solid evidence for ADHD-PI-specific genetic etiologies and differential responses of subtypes to ADHD medications.