Can ASD and ADHD Symptoms in Children with Autism Predict Early Attentional Disengagement in Their Infant Siblings?

Background: Studies with infants with older siblings with autism spectrum disorder (ASD) (probands) suggest that difficulties in visual disengagement may be one of the earliest emerging features of ASD (Zwaigenbaum et al., 2005; Elsabbagh et al., 2009; Elsabbagh et al., 2013). At 9-10 months, infant siblings of children with ASD took significantly longer to disengage from a central fixation and orient to peripheral stimuli compared to low-risk controls (Elsabbagh et al, 2009). To date, no studies have investigated whether ASD or attention-deficit/hyperactivity disorder (ADHD) symptoms in the proband predict attentional disengagement in their infant siblings. As ASD co-occurs frequently with ADHD, a condition in part characterized by attentional difficulties, there is a need to consider the role of ADHD symptoms in early attentional markers of ASD.  

Objectives: To examine the relation between ASD and ADHD symptoms in probands and attentional disengagement in their infant siblings at 8 and 14 months.

Methods: A cohort of 108 infants with an older sibling with ASD completed the gap-overlap task (Elsabbagh et al, 2009) at 8 months and 14 months.  In a series of trials, infants were presented with a central stimulus (CS) followed by a peripheral stimulus (PS); reaction time (RT) to saccade to the PS was measured using eye-tracking technology.  There were three conditions: Baseline (CS disappeared as PS onset), Gap (CS disappeared 200ms prior to PS onset) and Overlap (CS and PS on screen at the same time).  Key dependent variables at 8 month and 14 months were the number of trials in which the infant failed to saccade to the PS within 1.2 seconds of onset, and mean RT in the Overlap condition. Proband ASD symptoms were measured with the Social Communication Questionnaire (SCQ), and ADHD symptoms with the hyperactivity and inattention symptom subscale of the Strengths and Difficulties Questionnaire (SDQ) reported by the parents on the children with ASD (mean age = 7.05 years, S.D.=2.46; 91% male). 

Results: More severe proband ASD symptoms predicted more frequent disengagement failure (rho = 0.29, p<0.01), and slower disengagement times at 8 months (t=-2.61, p=0.01); but not at 14 months (rho = 0.03, p=0.73; t=-0.58, p=0.56; respectively). Proband ADHD symptoms did not relate to disengagement failure in infant siblings at either time points (all ps>0.30). However, more severe proband ADHD symptoms significantly predicted faster disengagement speed in the infant siblings at 8 months (t=-2.61, p=0.01) but not at 14 months (t=-0.58, p=0.56). 

Conclusions: Proband ASD and ADHD symptoms predicted infant sibling attentional disengagement at 8 months, but this effect was not observed at 14 months. While greater levels of ASD symptoms in probands related to greater difficulty with disengaging from the central stimulus, proband ADHD symptoms predicted faster orienting in overlap conditions. Our findings highlight the importance of taking into account ADHD symptoms when studying infants with familial risks for ASD.