Disparities in the Identification of Autism: The Influence of Sex, Family Income, and Cognitive Abilities
Exciting evidence has accumulated documenting the power of early intervention to promote long-term outcomes in autism spectrum disorder (Dawson, 2008; Zwaigenbaum et al., 2015). Thus, early identification of autism spectrum disorder (ASD) is an essential healthcare priority. Although symptoms of ASD may be present as early as infancy (Barbaro & Dissanayake, 2009), diagnosis typically lags far behind, with the majority of children not being identified until school-age or later (Shattuck et al., 2009). Identifying factors that influence the timing of first concern for ASD and the age of diagnosis is a critical research priority with the potential to reduce disparities in the early identification of ASD.
The current investigation used a large sample of children with ASD to examine multiple variables associated with autism identification, including age of first parent concern, diagnosis, time to diagnosis (time between first parent concern and diagnosis), and parental and clinician judgment of when symptoms of ASD were first present in hindsight. Sex, socio-demographic factors, and child cognitive abilities were considered as possible contributors to identification.
Children (N=653; 79% male) were identified with clinical diagnoses of ASD through the Province of Ontario Neurodevelopmental Disorders (POND) research network, a consortium of clinical and research sites in Canada. Parents reported on socio-demographic factors, age of first concern for ASD, and their judgment of when their child’s symptoms were first present in hindsight. Clinicians reported on their perception of symptom onset. Cognitive abilities were measured using gold-standard IQ measures, depending on child’s age at diagnosis.
Regarding descriptive statistics, age of first parent concern (M=21.71 months, SD=16.46 months) occurred early in development before year two. However, age of first diagnosis (M=58.84; SD=36.78 months) was delayed roughly three years after parents were first concerned. In hindsight, parents perceived that symptoms of ASD were likely present around one year (M=12.92 months), whereas clinicians reported that symptom onset likely occurred at around 18 months (M=17.97 months).
Regarding the role of sex in identification (see Table 1), females received their first diagnosis significantly later than males, and experienced a longer time to diagnosis despite no sex differences in age of first parent concern. Whereas there were no sex differences in clinician report of symptom onset, parents perceived an earlier age of first symptom onset for females than males in hindsight. Higher family income was associated with earlier first parent concern, earlier diagnosis, and earlier clinician report of symptom onset (see Table 2). Lastly, higher child verbal functioning related to later parent first concern, later identification, as well as later clinician report of symptom onset, with weaker and less robust findings for nonverbal cognitive abilities (see Table 2).
Results underscore difficulties in autism identification, as the average age of diagnosis lagged over three years behind first parent concern. Moreover, disparities in ASD identification were identified, with females, children with higher cognitive abilities, and families with lower income experiencing later identification. Implications for understanding and reducing healthcare disparities in autism diagnosis will be discussed.