The Comorbidity of ADHD and Autism Spectrum Disorders (ASDs) in Community Preschoolers

Abstract

Symptoms of inattention and hyperactivity, features of attention-deficit/hyperactivity disorder (ADHD), have been frequently documented in children with autism spectrum disorders (ASDs) and often co-occur. Evidence indicates that 20-50% of children with ADHD meet criteria for ASD, and 30-80% of ASD children meet criteria for ADHD.According to the DSM-IV, the essential features of Autistic Disorder (AD) are “the presence of markedly abnormal or impaired development in social interaction and communication and a markedly restricted repertoire of activity and interests”. Differential diagnosis of “Pervasive Developmental Disorder” (PDD: Autistic Disorder, Rett's Disorder, Childhood Disintegrative Disorder, Asperger's Disorder) and “Pervasive Developmental Disorder-Not Otherwise Specified”(PDD-NOS) is often difficult in the preschool child. This is particularly true when assessing verbal and nonverbal communication since both expressive and cognitive language are not yet established and there are many differences in their acquisition period among these children (before the age of three). As a result, many of these children are diagnosed with PDD-NOS not meeting the criteria for a specific type of PDD; this category includes "atypical autism" presentations that do not meet the criteria for AD. As a result, the concept of PDD-NOS has become a mixed bag. Often, diagnosis cannot be established before age three, delaying therapeutic interventions. Moreover, differential diagnosis between ADHD and PDD-NOS can be especially difficult, mainly in infant and young children. However, and following the recommendations of the DSM- IV, the ASDs diagnosis has been included among the exclusion criteria for the ADHD. Such exclusion has generated considerable controversy regarding the necessity and benefits of maintaining these separations.At present, a new edition of the DSM has been published: DSM-5® (Fifth Edition, 2013). Among the advantages that this new manual provides are: i) further categorization of the persons affected and ii) the possibility of diagnosis before the age of three. The DSM-5 takes into account that limitations in language are not specific to autism. The new diagnostic category “Social Communication Disorder” appears separate from ASD, which does not seek to create a new subcategory.In light of the new DSM-V criteria which allow a dual diagnosis of ASD and ADHD behaviors, in this chapter we will review the clinical overlap of these two conditions, particularly regarding their comorbidities in community pre-schoolers (generally categorized as PDD-NOS). We will also look into possible future research directions necessary to enhance our understanding of the etiology/genetics factors as well as the appropriate sequence of therapeutic interventions and pharmacological treatment (psychostimulant and nonstimulant medications) for the co-occurrence of these disorders.Keywords: Autism, Attention-deficit/ hyperactivity disorder, co-ocurrece, comorbidities, pre-schoolers, dual diagnosis, therapy, research