Investigating the Nature of Decreased Sound Tolerance in Autistic and Non-autistic Adults

Abstract

People vary greatly in their ability to tolerate sound in their environments, with the extremes of these individual differences resulting in clinically significant decreased sound tolerance (DST). DST can be further subdivided into the disorders of hyperacusis (wherein low/moderate-intensity sounds are excessively loud or physically painful), misophonia (wherein specific “trigger” sounds elicit extreme annoyance, anger, and/or disgust), and phonophobia (a specific phobia of certain sounds or sound-related situations/stimuli). Despite a sizable body of literature describing the construct of DST as a feature of autism spectrum disorder (hereafter “autism”) to date, there has been surprisingly little prior scholarship specifically focused on the phenomenology of DST in autism or comparing its mechanisms to that of DST with similar phenotypes in the non-autistic population. Thus, the present dissertation sought to fill this lacuna by conducting a thorough exploratory investigation into the “DST” construct space within both autistic and non-autistic adults. We conducted the first large-scale prevalence studies of DST disorders in the autistic population (n=936) finding clinically-significant hyperacusis, misophonia, and a combination of the two in 40.2%, 35.5%, and 27.0% of the sample, respectively, reflecting very large hyperacusis-misophonia overlap in this population. The following chapter examined the correlates of the two disorders in the same sample, finding subtle differential effects only in multivariate analyses. The psychometric properties of a novel self-report measure of DST symptomatology, (the Multidimensional Inventory of Sound Tolerance in Adults; MIST-A) were also investigated in a pooled sample of 2,807 adults (including 626 autistic adults) combined across five studies. The MIST-A demonstrated good psychometric performance, and a free online score calculator is available for use at https://asdmeasures.shinyapps.io/MISTA_score/. In a final pair of in-person laboratory studies, the perceptual and physiologic correlates of (interview-based) DST disorder diagnoses were systematically examined, observing for the first time that hyperacusis was associated with increased electrophysiologic latency-intensity growth slopes (for ABR wave V and N1b) and misophonia was associated with slower ABR wave V latency at fixed level (as well as marginally associated with increased positive slow wave responses). Autism did not moderate the effect of DST on any physiologic correlate tested in the laboratory study.