Decreased sound tolerance as a transdiagnostic feature of neurodiversity with loudness hyperacusis as a central player: A psychometric Bayesian analysis

BackgroundDecreased sound tolerance (DST) – an expression of sensory over-responsivity (SOR) – is a major source of impairment for many autistic individuals. DST/SOR shows a linear, polygenically inherited relationship with autistic traits, suggesting endophenotypic and dimensional properties. DST has also been reported in ADHD and other neurodevelopmental conditions, albeit less studied so far. As a step towards systematic understanding of DST expressions across the full neurodevelopmental spectrum, we aimed to clarify how specific DST subtypes (hyperacusis, misophonia, and phonophobia) vary in association with diagnosed neurodevelopmental conditions as well as continuous traits measures. MethodsAdults 18–68 years old (n = 412) without neurological disorders or hearing loss participated anonymously in the study. The sample was enriched in autism and ADHD (26% autistic, 24% ADHD) but also included participants with other neurodevelopmental conditions. We administered web-based questionnaires to collect demographic and clinical information, self-reported symptoms of loudness hyperacusis, misophonia, and phonophobia, as well as traits of autism, ADHD, and developmental coordination disorder (DCD). We used Bayesian statistical methods to understand DST subtypes as functions of both categorical diagnoses and continuous neurodevelopmental traits. ResultsAll three DST subtypes were elevated in both autism and ADHD at similar levels, compared to individuals with no diagnosis. Models containing both diagnoses outperformed single-diagnosis models for all DST subtypes. Continuous neurodevelopmental traits predicted DST severity independently of diagnostic status, with combined trait models explaining 32–48% of variance. Misophonia and phonophobia symptoms were strongly contingent on loudness hyperacusis. ConclusionsDST reflects a transdiagnostic dimension of neurodivergence rather than an autism-specific feature, and loudness hyperacusis appears to be a dominant DST pattern. The findings support the value of considering the full spectrum of neurodevelopmental variation in DST studies, rather than siloing analyses within narrow diagnosis groups. Further studies on loudness hyperacusis might be especially impactful for neurodivergent individuals.