The roles of sensory hyper and hyposensitivity in infancy in understanding later anxiety and emerging autistic traits

Background: Existing evidence indicates that atypical sensory processing is a core characteristic of autism, and has been linked to both anxiety and repetitive behaviours. However, most work has used cross-sectional designs and not considered the differential roles of hyper and hyposensitivity to sensory inputs, and is thus limited in specificity. Methods:161 infant-siblings participated in a longitudinal study. All participants either had at least one older-sibling with a diagnosis of autism (elevated-likelihood-autism, EL-ASD; n=80), or a first degree relative with attention-deficit hyperactivity disorder (ADHD) (elevated-likelihood-ADHD, EL-ADHD; n=31) or both (EL-ASD/ADHD, n=21)), or had no known immediate family members with a diagnosis of autism or ADHD (typical-likelihood, TL, n=29). Parents rated infant manifestations of anxiety (fearfulness) using the Infant Behavior Questionnaire at 10 and 14 months, and the Early Childhood Behavioral Questionnaire at 24 months, and sensory hyposensitivity and hypersensitivity at 10, 14 and 24 months using the Infant Toddler Sensory Profile. Domains of autistic traits (restrictive and repetitive behaviours; RRB, and social communication impairments, SCI) were assessed using the parent-rated Social Responsiveness Scale at 36 months. Cross-lagged models tested 1) paths from fearfulness and hypersensitivity at 10-24-months, and between fearfulness and hypersensitivity to later autism traits, 2) the specificity of hypersensitivity effects by the inclusion of hyposensitivity as a correlated predictor. Results: Hypersensitivity at 14 months was positively associated with fearfulness at 24 months, and hypersensitivity at 24 months was positively associated with SCI and RRB at 36 months. When hyposensitivity was included in the model, paths between hypersensitivity and anxiety remained, but paths between hypersensitivity and autistic traits became non-significant. Conclusions: Hypersensitivity may be one of the earliest predictors of infant anxiety. Although sensory atypicalites in infancy are associated with later autism traits, given the overlap between hypo and hypersensitivity, more research is needed to understand the specificity of effects.