Date of Award


Document Type

Open Access Thesis



First Advisor

Jane E. Roberts


Fragile X syndrome (FXS) and autism spectrum disorders (ASD) are characterized by deficits in social interactions (reduced eye contact, topic preoccupation, and social withdrawal) and maladaptive behaviors of anxiety, social withdrawal, and restricted interests (Kau, Tierney, Bukelis, Stump, Kates, Trescher et al., 2004). Prior research with individuals who have FXS has indicated that problem behaviors (i.e. social withdrawal and inattention) were correlated with abnormal activation of the hypothalamus-pituitary-adrenal axis (HPAA; Hessl, et. al., 2002); however, very few studies have investigated physiological patterns and associations with social dysfunction and restricted and repetitive behaviors for individuals with idiopathic ASD. The present study investigated the role of cortisol stress response physiological indices on directly observed social affect deficits, repetitive behaviors and overall autistic behaviors within adolescent to young adult males with FXS compared to idiopathic ASD. The study involved two related analyses: 1) examination of mean levels and modulation of salivary cortisol levels in response to two days of assessments and 2) the investigation of the relationship of social affect deficits, restricted and repetitive behaviors and overall autistic behaviors to salivary cortisol stress responses. Adolescent males with FXS with and without ASD demonstrated elevated pre-assessment cortisol levels on Day 1; however, persistent elevation in cortisol stress response at the start of Day 2 was only found in adolescent males with ASD (idiopathic and with FXS). The greatest modulation of cortisol stress response was found in adolescent males with FXS-O on Day 1 with exact opposite findings on Day 2 with adolescent males with iASD demonstrating the greatest modulation of cortisol stress response. Lastly, lack of modulation of cortisol stress response on Day 2 was predictive of greater social affect deficits in adolescent males with iASD. Adolescent males with iASD and FXS with ASD have distinct neuroendrocrine profiles that differentiate them from FXS alone. Additionally, increased physiological reactivity during testing sessions was associated with greater restricted/repetitive behaviors regardless of genetic or diagnostic status. The results also support a complex interplay of maladaptive cortisol modulation and association with social affect deficits in young adult males with idiopathic ASD.

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