Sunlight feels too bright. Fluorescents become unbearable. The background music in a restaurant becomes physically painful. The auditory and visual thresholds the survivor lived with for forty years dropped during the experience, and they did not come back up.
The pattern is consistent. Within weeks of the experience, the survivor notices that the world has gotten louder and brighter without changing. They wear sunglasses indoors. They start asking restaurant managers to turn down the speakers. They cannot watch action movies in the theater anymore because the volume hurts their chest. They cannot sit under the overhead fluorescents at the office without getting a headache.
This is not hypersensitivity in the diagnostic sense, where a clinician can map it to vestibular damage or migraine pathology. The eyes test normally. The ears test normally. The threshold for pain and overwhelm at the sensory level just shifted, in both directions: dim light is more legible, soft sounds are more audible, and the loud end of the range that used to feel normal now feels like assault.
"The first thing I noticed when they let me out of the hospital was that the world was screaming. The traffic was screaming, the radio was screaming, my wife was not screaming, but I could hear three rooms of the house at once and it was all too much. We had to take down the kitchen radio. I wore sunglasses for a year. People asked me if I had a migraine. I did not have a migraine. The volume on the world had been turned up." — composite, drawn from Atwater's interview transcripts and Ring's Heading Toward Omega (1984)
The most-cited triggers in the survivor literature: fluorescent tubes (particularly older T12 ballasts that flicker at 120 Hz), sodium-vapor parking-lot lights, supermarket overheads, cinema sound systems, restaurant playlists at evening volume, leaf blowers, car alarms, and the high-pitched whine of cathode-ray displays in the era when those still existed. The migration to LED lighting and flat-panel displays helped a measurable subset of long-term experiencers, which is one of the few pieces of indirect evidence that the sensitivity is real and is keyed to specific frequency content rather than being a generalized anxiety symptom.
Autonomic nervous system reset. The leading clinical hypothesis. The experience involves an extreme state of physiological stress (cardiac arrest, severe trauma), and the autonomic system recalibrates afterward. Hyperacusis and photophobia are documented sequelae of brainstem stress in non-NDE populations. The objection is that those populations usually recover within months. NDE-related sensitivities are stable at decade-plus follow-up, which the autonomic-reset model does not predict.
Sensory gating change. Greyson and others have proposed that the experience reduces the brain's normal filtering of sensory input. The thalamus and the prefrontal cortex ordinarily suppress most of the signal entering the body, so that only relevant information reaches conscious awareness. After the experience, the suppression is partially lifted. The survivor receives more of the raw input. Light feels brighter because more of the photon count is reaching attention. Sound feels louder for the same reason.
Comparison to psychedelic and mystical states. Long-term meditators, ayahuasca veterans, and people who have had spontaneous mystical experiences report similar sensitivity profiles. The current best guess is that the underlying mechanism is the same: a permanent reduction in default-mode-network filtering. The work of Robin Carhart-Harris and colleagues at Imperial College on the entropic brain model gives the cleanest current physiological framework for this.
Long-term experiencers tend to redesign their environments. Lower-wattage warm bulbs. Sound-treated rooms. Headphones on long flights. Restaurants chosen by acoustic quality. Some move out of cities altogether. The strategy is environmental, because the sensitivity does not respond to the standard interventions (gabapentin, SSRIs, ear plugs, exposure therapy) the way clinical hyperacusis sometimes does.