4 - Differential Diagnosis

Abstract

Shifts in terminology, increases in the prevalence estimates of ASD, early identification, and interest in the assessment of adults with ASD have been key characteristics in recent decades of research. This chapter focuses on etiological issues, prevalence estimates, lifespan development, differentially diagnosing within the spectrum, comorbid psychopathology and differential diagnoses, and current assessment methods available to assist in the diagnosis of ASD. There are two key factors that have inspired and influenced efforts to reliably diagnose ASD in very young children. The first is the belief that the earlier one can identify a child with developmental difficulties, the earlier one can provide treatment. A second factor is that many parents of children with autism report that they noticed changes in their child’s behavior between 1 and 2 years of age. However, careful clinical interviewing, including a detailed developmental history, and the use of empirically based measures are critical. Some disorders mimic symptoms and/or features of ASD such as intellectual deficits, language problems, tics, feeding problems, sleeping problems, repetitive behaviors, and hyperactivity, and further complexity is added when comorbidity is considered. The chapter also provides an overview of measures (i.e., interviews, observation systems, clinician-rated scales, and informant-rated scales) used to assess and diagnose ASD. It includes measures that are more commonly used as well as some newly developed measures. Although most are developed for the assessment of children, some are designed for assessing adults.