Why a partner’s chewing can fill people with rage: Canadian researchers helping unravel ‘misophonia’

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A paper by pioneers in the field who coined the term misophonia in 2001 — the literal translation is “hatred of sound” — described how a teenager was triggered by the sound of his stepmother’s footsteps “who was purposely following (him) to make his life miserable.”

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Scientists who developed a test for psychoacoustic (how the brain perceives sounds) to assess for misophonia say the reactions can be more intense when it’s impossible to escape the situation, such as being on a plane. “Also, eating and chewing sounds are less annoying when originating from babies or animals, as it is ‘not their fault’ if they are generating them,” the authors wrote.

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Trigger sounds are often, though not always, human produced. Some are sensitive to the sounds of dogs barking, licking or eating, or the sound of a cat’s claws clicking on a hard surface.

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“Often it’s a lot of (human) mouth sounds, so things like family dinners become a problem,” Scheerer said. “You can’t sit with your spouse at dinner because watching or hearing them chew is so distressing.”

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One anecdote that has stayed with her is the story of a mother whose autistic daughter ate her lunch in a bathroom stall because she couldn’t tolerate the sounds of other children chewing in the school cafeteria.

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Misophonia sometimes co-occurs with autism, as well as obsessive compulsive disorder and anxiety.

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Hyperacusis is a sister disorder linked to perceived loudness, “the important part of that being ‘perceived,'” Scheerer said. People have a reduced tolerance to normal sounds at levels most people perceive as perfectly harmless or tolerable. For some, those sounds seem excessively loud or uncomfortable; others experience actual physical pain.

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Problematic sounds “can range from distant traffic to nearby electric mixers,” Scheerer and colleagues wrote in the journal article. “Often those with hyperacusis report irritation, annoyance, distraction, stress, fatigue, pain and fear, to name only a few emotions.”

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With both forms of DST, people begin avoiding certain places — restaurants, cafeterias. People withdraw from social situations; they experience conflict at work. Noise-cancelling headphones can help, but we live in a sensory-rich world. Sounds are everywhere. “As soon as you completely block out sound, you’re losing all the richness of the environment,” Scheerer said.

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The alternative is “tiptoeing around in a world where you don’t know what’s going to set you off next,” she said.

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“You could imagine how that could wear on a person over time.”

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Scheerer has been doing a lot of university work, in addition to work with children and youth, trying to understand how early it develops. University lecture halls (laptops, cellphones, people drinking, snacking, sniffing), dormitories, dining halls, food courts — all produce elevated levels of triggering sensory stimuli, Scheerer said.

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It’s difficult to know how many people are affected, because most studies rely on self-reported questionnaires. Estimates land as high as the one in five range, or 18 per cent of the adult population. Data from Scheerer’s work suggest 12 to 18 per cent of post-secondary students qualify for clinical misophonia. A smaller study out of Dalhousie University of 606 young adults aged 19 to 32 found about nine per cent met the cutoff for significant hyperacusis; a similar proportion met criteria for moderate or greater misophonia severity.

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Researchers are still struggling to tease out the underlying mechanisms for both conditions, examining different brain regions and networks, and the extent of dysfunction. “Is it related to attention? Conditioning? Is it more basic, like neural hyper-excitability? We don’t quite know,” Scheerer said. Most research suggests it’s not one thing, but a combination.