Timing of ASD Diagnosis: Demographic Factors of Influence

Background:  The average age of diagnosis among children with Autism Spectrum Disorder (ASD) exceeds 4 years, often with a significant lag between parent first concern and diagnosis. While studies have investigated the impact of demographic factors on likelihood of ASD diagnosis, their impact on the timing of diagnosis is less clear. Girls and high functioning children may be more likely to experience significant diagnostic delays given current (and historic) public perception of the disorder.

Objectives:  Data are from a multi-site study focusing on multimodal neurogenetic exploration of girls (and boys) with ASD. In a sample of children with ASD without intellectual impairment, we explore the effects of parental education, household income, child gender, and child birth-order on parent report of the timing of ASD diagnosis.

Methods:  Preliminary data were analyzed from one site and included 43 children (26 males; 8-17 years) with ASD (mean IQ=104.4, SD=21.2). Parents completed a demographic questionnaire, medical history interview, and Autism Diagnostic Interview Revised. In order to analyze the influence of child gender, we matched a subsample of 17 ASD males and 17 ASD females on age and IQ. Additional data from other sites will be included in the final analyses.

Results:  Children who had two parents with less than a bachelor’s degree (non-BA), were diagnosed with ASD at a significantly later age (M=111.7, SD=52.9) than children with one parent with at least a bachelor’s degree (BA-1; M=66.8, SD=31.2, p=.02), and children with two parents with at least a bachelor’s degree (BA-2; M=66.8, SD=32.6, p<.01). Children in the non-BA group also experienced a significantly longer delay (M=109.2, SD=24.5) from age of parental first concern to age of ASD diagnosis, than children in the BA-1 (M=51.8, SD=28.7, p<.01) and BA-2 (M=58.5, SD=37.4, p<.01) groups. There was no effect of household income on timing of diagnosis.

In our IQ- and age-matched subsample, time between age of first concern and ASD diagnosis was marginally longer for females (M=76.1, SD=44.5) than males (M=52.8, SD=30.3, p=.09). Later-born females (M=108.3, SD=32.6) were diagnosed with ASD at a later age than later-born males (M=58.5, SD=29.5, p=.04).

Conclusions:  Children whose parents have more formal education were diagnosed with ASD at an earlier age and experienced a shorter delay between parent concern and ASD diagnosis. These findings suggest that higher parent education, separate from household income, influenced timing of diagnosis. Males also experienced a marginally shorter wait time between parents’ first concern and ASD diagnosis than females, particularly for later-born children. Gender did not significantly effect age of ASD diagnosis, but data collection is on-going and additional data from 3 other sites will be available. Together, our findings suggest an influential role of both parent education and child gender in the timing of ASD diagnosis even within children with higher functioning ASD outcomes.