Autism Spectrum Disorders (ASDs) are defined by impairments in social- communication skills and restricted, repetitive and stereotyped patterns of behaviors and interests. The presentation of symptoms is affected by a variety of factors not specific to ASD, such as developmental characteristics (e.g., age, language level, and cognitive ability) and co-occurring dimensions of behavior (e.g., internalizing and externalizing behaviors). With the shift toward a dimensional diagnostic system put forth by the DSM- 5, research is needed to explore the influence of non-ASD-specific factors on scores from widely-used ASD diagnostic instruments. This research will inform the development of new measures that take into account the interaction between ASD symptoms and non- ASD-specific dimensions of behavior in order to provide more appropriate quantitative measures of ASD symptoms.
This three-study dissertation seeks to expand the valid use of pre-existing ASD diagnostic measures with individuals across a range of ages. Study One provides a systematic look at the influences of developmental characteristics and non-ASD-specific dimensions of behavior on interpretation of scores from the Social Responsiveness Scale (SRS), a parent questionnaire widely used as an index of ASD severity. The second two studies focus on the Autism Diagnostic Observation Schedule (ADOS). Study Two standardizes Social Affect and Restricted, Repetitive Behavior domain scores to provide separate measures of social-communication and repetitive behavior severity that are less influenced by developmental level. Study Three revises the diagnostic algorithm and calibrates scores for ADOS Module 4, used with verbally fluent older adolescents and adults. This increases Module 4’s comparability to other modules used with younger or more language impaired individuals.
Overall, the results of these studies provide a more in-depth understanding of how ASD diagnostic measures are influenced by developmental characteristics and non-ASD- specific dimensions of behavior. This knowledge can inform use of these measures as quantitative indices of ASD symptom severity. In clinical settings they may be used to monitor treatment progress. Application in the research domain may facilitate exploration of links between biological mechanisms and behavior and predictors of adult functioning, which will hopefully inform development of targeted interventions to promote positive outcomes for individuals with ASD.PHDPsychologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/107055/1/vhus_1.pd
