<p>Decreased sound tolerance — a group of conditions characterized by a reduced ability to cope with everyday sounds that are tolerable for most people — often co-occurs with mental health disorders such as autism spectrum disorder, attention deficit hyperactivity disorder, anxiety disorders and obsessive–compulsive disorder. However, studying decreased sound tolerance within siloed diagnostic entities has limited advances in this field. In this Review, we focus on hyperacusis and misophonia (two frequent subtypes of decreased sound tolerance) to synthesize findings across diagnostic boundaries and to offer a transdiagnostic view of these subtypes’ prevalence, potential underlying mechanisms, tools for diagnosis and treatment, mental health correlates and impact. We argue for a holistic approach that delineates shared and unique features of decreased sound tolerance subtypes and the relationship between sensory processing and differences in mental health disorders. Moving towards an integrated understanding of how decreased sound tolerance emerges across different clinical presentations requires recognizing the transdiagnostic nature of these mechanisms.</p>