For many of us, Christmas dinner is a bonding experience where family and friends break bread and share stories while stuffing ourselves silly. It’s the one time where sheer gluttony is more or less expected. But for those with a rare, newly recognised disorder called misophonia, the mere thought of such a meal inspires only anxiety and dread.

People with misophonia hate certain noises – termed “trigger sounds” – and respond with stress, anger, irritation and, in extreme cases, violent rage. Common triggers include eating noises, lip-smacking, pen clicking, tapping and typing. All those noises can drive a person with misophonia to avoid family gatherings altogether. And worse, feelings of aggression tend to be amplified if the sounds are coming from those with emotional ties to the sufferer, such as family members.

“I haven’t eaten with my parents, at least without earplugs, in over a decade,” says Meredith Rosol, a 25-year-old teacher who was diagnosed with misophonia two years ago after years of hypersensitivity to sound.

“I was six years old, and it started with my parents chewing at the dinner table,” she recalls. Her list of triggers grew longer: chewing (especially crunchy foods), tapping, typing, heavy breathing, cutlery clinking, foot shuffling. Even certain sights started upsetting her, such as foot-shaking and fidgeting. At school, typical classroom noises – chalk scraping against the blackboard or the hum of a radiator – made her skin crawl. “It’s like a fight-or-flight response: your muscles get tense, you’re on edge, your heart races, and you feel the urge to flee,” Rosol says.

The term misophonia, meaning “hatred of sound”, was coined in 2000 for people who were not afraid of sounds – such people are called phonophobic – but for those who strongly disliked certain noises. Set off by stimuli that vary from person to person, the reaction, sufferers say, is like being punched in the stomach or repeatedly stung by bees.

In 2013, a group of Dutch psychiatrists laid out the condition’s diagnostic criteria and urged that it be classified as its own psychiatric disorder. Even though misophonia is a new term, thousands of people have been describing its effects on them for years and joined such online support groups as Yahoo’s selective sound sensitivity group and Reddit.com’s misophonia subreddit.

No one knows what causes the condition, so designating a standard treatment has been a problem, but experts seem to agree that misophonia isn’t so much about the sounds themselves as their context. “Sometimes their responses are localised around certain people: they might be bothered by their mother’s chewing but not their brother’s,” said Miren Edelstein, of the University of California at San Diego who has researched misophonia.

As part of a small study, Edelstein interviewed a number of self-identified misophonics and found that the fight-or-flight emotion arises only in specific circumstances. For instance, they didn’t mind their own chewing or typing noises, or sounds made by animals or babies. A teacher of autistic children, Rosol said she doesn’t usually get triggered by her students, even in the bustling cafeteria.

Edelstein and her colleagues also hooked up electrodes to volunteers’ hands to verify that their aversion to certain sounds was real. “Prior to our study, we only had anecdotal evidence that misophonia was a real thing,” she said. “So we wanted to take the first step in providing objective physiological evidence.”

Self-described misophonics listened to a series of sounds and rated their discomfort level for each one; so did volunteers who served as a control group. The electrodes measured the electrical conductance of their skin, a well-accepted measure of physiological arousal. Sweat glands in the hands are especially sensitive to emotional stimuli, and skin becomes a better conductor in the presence of more sweat.

When misophonics’ discomfort ratings were high – say, during a sound bite of gum chewing or chip eating – their skin conductance shot up. But when they heard more soothing sounds, such as rainfall, they did not have a sweat reaction. In other words, they are not likely to be lying about having that sudden negative emotional response kick in.

But where does this intense reaction come from, if it’s not caused by the noises alone? “In my opinion, misophonia is a learnt conditioned response,” said audiologist Dr Natan Bauman, of the Hearing, Balance and Speech Centre in Connecticut. “If we associate a given event – in this case, all those trigger sounds – with something that is perceived to be a danger, then we need to act on it accordingly.”

He has seen close to 100 misophonics in his private practice and doesn’t believe misophonia is a hard-wired phenomenon. Rather, he thinks his patients at some point made a negative association with certain sounds and so have an impulsive reaction to them.

This impulse has to do with how the brain processes sound. Sound waves cause tiny bones in the middle ear to vibrate. Hair cells inside the cochlea, a spiral-shaped cavity in the inner ear, transform the vibrations into electrical signals that travel down the auditory nerve to the brain. The signal reaches the thalamus, a part of the brain that acts like a central switchboard for sensory information. From the thalamus, the signal follows two different paths to the amygdala, which is located deep in the brain and is involved in the processing of emotions such as fear and pleasure.

“Some people think the amygdala is mostly for fear-related emotion,” says Dr Josef Rauschecker, director of the Laboratory for Integrative Neuroscience and Cognition at Georgetown University. “The amygdala is a fairly old part of the brain, and our fears are pretty primordial.”

One of the two routes is a direct pathway from the thalamus to the amygdala, enabling an immediate response that leads to an emotional reaction. The advantage of this direct route is speed: you hear a loud bang, and fear prompts your body to rapidly and automatically jump.

The other route is longer and goes first to the medial prefrontal cortex before reaching the amygdala. The medial prefrontal cortex is a more evolutionarily advanced part of the brain that can regulate emotions and allow for a more discerning interpretation of a situation. The original signal splits and heads out on the two roads at the same time, but the signal travelling the longer route obviously takes longer to process.

“What happens with those who have misophonia, in my opinion, is that there is no involvement of this longer route, the more-refined route,” Dr Bauman says.

Dr Rauschecker agrees and speculates that misophonia might have something to do with damage to the medial prefrontal cortex, similar to what he found with another condition, tinnitus. Tinnitus is phantom ringing or other noise in the ear, a perception commonly caused by damaged hair cells in the cochlea.

“Say you go to a loud disco and you lose some hair cells,” Dr Rauschecker says. “The ringing lasts for a day or two, and then it disappears again.” The ear hasn’t repaired itself. Rather, the medial prefrontal cortex can help tune out the phantom ringing. But for some people, the ringing never goes away. In 2006, Dr Rauschecker and his colleagues found that tinnitus patients had significantly less volume in the medial prefrontal cortex than control participants without tinnitus. “I would include misophonia as a subtype of tinnitus, probably,” he says.

Regardless of its cause, misophonia makes life difficult for those who have it and for the people around them. Those with extreme cases say they sometimes hole themselves up at home to avoid social situations and public places for fear of having something trigger a negative reaction.

A few treatment options do exist, but there is no cure. Dr Bauman and other audiologists sometimes mix cognitive behavioural therapy and in-ear devices that emit white noise to drown out triggers. The hope is to reduce the white noise enough that the patient doesn’t need to wear the device any more; some patients have reached that point, he says.

Rosol, whose sensitivity began when she was six years old and her parents chewing upset her, has found her own remedies: a white-noise machine and earplugs in bed and noise-cancelling headphones at the gym and on public transport. At meals, she wears a single earplug and blocks the other ear with her hand when others start chewing loudly.

At large family gatherings, she uses earplugs during the meal and specifically avoids sitting next to her parents. Because she can’t hear what’s being said, she usually doesn’t contribute to the conversations. It’s not always ideal, Rosol says. “I usually finish earlier than everyone, go to the kitchen to clear my plate, and wait in another room.”