(PS3-B30) The Influence of Diagnostic Overshadowing on Age of Diagnosis of Autism Spectrum Disorder

Early diagnosis of Autism Spectrum Disorder (ASD) is associated with positive outcomes, such as increased social communication skills (Fuller & Kaiser, 2019). In light of this, increasing empirical attention has been directed toward examining various demographic factors (e.g., socioeconomic status, child race) that may influence the age of ASD diagnosis in an effort to promote greater equity in the diagnostic process (Nowell et al., 2015). More recently, the presence of other, co-occurring conditions has been considered as a potential impediment to a timely ASD diagnosis (Mazefsky et al., 2012; Rosen et al., 2018). The majority of autistic individuals experience at least one co-occurring condition which may increase their risk of a delayed ASD diagnosis (Leyfer et al., 2006; Simonoff et al., 2008). The present study compared the age of ASD diagnosis with the age of diagnosis of multiple co-occurring conditions in a sample of 82 children and adolescents, aged 11-20 (M = 13.81, SD = 1.96). An ASD diagnosis was given later, on average, in the presence of co-occurring ADHD (2.18-year delay) and a learning disability (.7-year delay). Conversely, an ASD diagnosis was given before, on average, a diagnosis of anxiety (1.07 years prior), disruptive behavior disorder (.25 years prior), an intellectual disability or cognitive delay (1.57 years prior), obsessive-compulsive disorder (1.5 years prior), mood disorder (4 years prior), and Tourette’s/Tic Disorder (6 years prior).

The average age of ASD diagnosis obtained in the sample is 7.84 (SD = 3.88), which is over five years later than when autism can be reliably diagnosed (Lord et al., 2006). Previous research has identified demographic variables that hinder a timely diagnosis of ASD and thereby delay access to services when they would be maximally effective in early development. The findings of the present study also suggest that the phenomenon of diagnostic overshadowing is at play, which occurs when a healthcare professional falsely attributes a person’s symptoms to a preexisting condition when such symptoms actually suggest the presence of a co-occurring condition. This underscores the need for additional provider training in identifying and conceptualizing ASD in the context of other conditions.