Earlier ASD Age of Onset Is Associated with More Amounts and More Severe Restricted and Repetitive Behaviors

Background:  Restricted and repetitive behaviors (RRBs) are a core feature of Autism Spectrum Disorders (ASD) (DSM-V, 2013) that can interfere with many aspects of daily functioning (Richler, Heurta, Bishop, & Lord, 2010). For some children, these impairing behaviors are present from as early as 20 months of age (Cox et al, 1999). Moore and Goodson have also shown that the total number of RRBs tend to increase between 2 and 4 years of age (Moore and Goodson, 2003). While research has indicated a relationship between age and RRBs (Richler et al, 2011; Cox et al, 1999; Moore & Goodson, 2003), less is known about the specific relationship between the age of onset of ASD symptomatology and the presence and severity of RRBs.

Objectives:  In this study, we explored the role of age of onset of ASD symptoms on the total number of RRBs and the severity of RRBs.

Methods:  A sample of 473 participants (82% male) aged 36-272 months (SD=48.3, Mean=98.7) were examined for the current study. The Autism Diagnostic Observation Schedule (ADOS) (Lord et al, 2003) and Autism Diagnostic Interview-Revised (ADI-R) (Rutter et al, 1994) was used to verify ASD diagnosis for all participants. The ADI-R was used to evaluate participant’s age of onset of symptoms (Question 87). The Behavior and Sensory Interest Questionnaire (BSIQ) (Hanson et al, 2016) was administered to evaluate the total number of RRBs and the severity of those RRBs. Descriptive statistics, a Spearman Rank Test and Mann Whitney U Tests, as the data was not normally distributed, were used to determine the relationship between age of onset and the presence and severity of RRBs. Consistent with prior research, we used norms for early age of ASD onset that have already been set in the field: Early Onset is defined by ASD symptomatology noticed before or at 2 years of age (Baraneck, 1999; Werner et al., 2000), while Late Onset is defined by ASD symptomatology noticed after 2 years of age (Palomo, Belinchon, & Ozonoff, 2006).

Results:  Age of Onset was negatively correlated with total amount of RRBs overall ((r(473) = -0.080, p = 0.081) and the total amount of severe RRBs (r(473) = -0.114, p=0.013). Children who experienced Early Onset had significantly more RRB symptoms than children who experienced Late Onset (p=0.019).

Conclusions:  Overall, children with Early Onset present with more RRBs overall and more severe RRBs than children with Late Onset. This indicates that there is a relationship between age of onset of ASD symptoms and the presence and severity of RRBs. Additional studies evaluating the effect of services provided to the child may be a potential mediator between age of onset of symptoms and RRBs.