Study Finds Tinnitus Activates 'Fight or Flight' Response in the Body

New findings indicate that persistent tinnitus could elevate stress levels by keeping the body in a near-constant state of alert to sound. Scientists analyzing facial cues in individuals with and without tinnitus discovered distinct involuntary facial movements and enlarged pupils linked to heightened threat perception in those suffering from the condition.

By cataloging these subtle facial expressions, the research team, led by neuroscientist Daniel Polley from Mass General Brigham, could even predict how severe a participant's tinnitus was. The study suggests that people with chronic tinnitus may react to ordinary sounds as if they were dangerous, reflecting an ongoing hyper-vigilant state.

"For the first time, we identified a measurable signature of tinnitus severity," said Polley. "We did not anticipate that sounds would trigger facial movements, and it was surprising to find that these expressions provide the most precise indicator yet of tinnitus-related distress."

Tinnitus is characterized by a persistent ringing, buzzing, or clicking in one or both ears that only the person experiencing it can hear. Its causes remain largely unknown, and there are currently no objective clinical tests to measure it, making diagnosis and monitoring challenging. Some individuals report relief through sound therapy, cognitive behavioral therapy, or tinnitus retraining therapy, though no definitive cure exists.

Chronic tinnitus, defined as lasting six months or more, affects over 120 million people worldwide. The condition can be severely disruptive, interfering with sleep and daily life, and is closely linked to anxiety and depression. Reliable biomarkers for the condition could improve understanding, diagnosis, and treatment development.

The study utilized facial microexpressionsbrief, involuntary facial movements that reveal emotional responses. Polley and his team recruited 97 participants: 47 with tinnitus or sound sensitivity and 50 without. Participants listened to a variety of sounds ranging from pleasant (soft music, laughter) to neutral (background chatter, paper rustling) to unpleasant (sirens, screeching metal), while their facial responses and pupil sizes were recorded.

In tinnitus-free participants, microexpressions corresponded to sound type: smiles for pleasant sounds and frowns for unpleasant ones. Those with tinnitus exhibited minimal facial responses to all sounds, but their pupils dilated significantly for every sound, unlike the control group whose pupils only expanded for the most aversive sounds. These physiological markers enabled researchers to assess both the presence and severity of tinnitus in participants.

Traditional theories suggest tinnitus may result from the brain amplifying auditory signals to compensate for hearing loss, but this cannot fully account for symptom severity. Polleys research highlights that tinnitus involves complex, body-wide responses to perceived threats, explaining the distress experienced by patients.

The study was published in Science Translational Medicine.

Author: Ava Mitchell