Physiological Characteristics Associated with Anxiety In Adolescents with Autism Spectrum Disorders

Background:  Adolescents with autism spectrum disorders (ASD) are at increased risk for the development of associated psychiatric symptoms, particularly anxiety. Such symptoms can further impair functioning and quality of life. There is considerable symptom overlap between anxiety and ASD, and it is unclear whether they represent separate disorders in affected individuals. Elucidating biological underpinnings of such symptoms has the potential to clarify this phenomenon. Psychophysiological methodologies, such as fear potentiated startle response, are non-invasive measures that have been widely utilized in the non-ASD population to facilitate better understanding of neural and physiological correlates (e.g., amygdala function) of anxiety. Such techniques can be applied to the ASD population to elucidate biological underpinnings of reported symptoms or to characterize clinical subgroups within ASD.  

Objectives:  To investigate the relationship between anxiety symptoms and physiological response, as measured by eye blink intensity (electromyographic activity; EMG) and skin conductance level (SCL) during a fear potentiated startle paradigm, among adolescents with ASD and typically developing adolescents; and, to determine whether this relationship differs as a function of group.

Methods:  Twenty adolescents (ages 13-17.5 years) with ASD and 22 typically developing adolescents underwent diagnostic and cognitive assessment as part of the Autism Center of Excellence study at the University of Washington. Presence of anxiety symptoms was assessed using parent-report (Child Behavior Checklist) and child-report (Revised Children’s Manifest Anxiety Scale). Eyeblink response (EMG) and SCL were collected during a fear potentiated startle paradigm. The relationship between symptoms of anxiety and physiological response was investigated for both groups using hierarchical linear modeling.

Results:  As expected, adolescents with ASD displayed significantly more anxiety symptoms than typically developing adolescents. No group differences were found in overall SCL or EMG response over time, or baseline SCL. Both groups showed potentiated conditioning according to EMG, evidenced by larger response to threatening stimuli. However, only teens with ASD demonstrated this enhanced physiological response based on SCL. For individuals with ASD, higher levels of reported anxiety symptoms were associated with larger initial and overall EMG response, which tended to decrease over time.

Conclusions:  Findings suggest that adolescents with ASD with high reported levels of anxiety symptoms exhibit enhanced physiological response compared to typically developing teens, most likely reflecting hyper-responsivity of the amygdala. This propensity for hyperarousal may contribute to the expression of anxiety in individuals with ASD.