Neurological Condition
Misophonia is a neurological condition affecting the auditory sensory processing function of the brain. It is not considered to be psychological in origin, but like other involuntary conditions such as tourettes, pyschology and emotional state can affect the extent of the triggers.
When a person suffering from misophonia hears a trigger sound, their flight or fight response will engage. This usually produces a reaction along a sliding range between Panic and Rage, with most experiencing a mix of both. The wide spread use of the term "Fight for Flight" has normalized the idea of this reaction in the main stream media. In light of this it is worth remembering that when the "Fight or Flight" mode is triggered, the brain believes itself to be in a life or death situation. This is the same part of the brain that is activated when suffering from PTSD (post traumatic stress disorder), the difference in this respect is the trigger and cause.
It will put the person into a state where they are ready to, quite literally, fight to the death to save their life. The severity of the reaction is often very extreme. This is why the term "Rage" is often used in regards to misophonia. "Anger" is not enough. It does not capture the full severity of the reaction. Severe disgust and even nausea can be felt also.
Visual triggers exist alongside auditory. For some, seeing the action that corresponds with the noise can be enough to trigger a response without even hearing the sound itself. For others a visual trigger might be a repetitive movement, someone bouncing their knee up and down for example.
How and why these noises and visual cues trigger such an extreme emotional response is as yet unknown. Quite frequently misophonia will exist comorbid (alongside) other disorders such as OCD. It can be sometimes difficult to know whcih came first, if either did at all, in relatoin to OCD. The anxiety caused by misophonia can itself be a cause of OCD, though in some the OCD seems to have been present before the emergence of misophonia.
The most common ages that symptoms appear are between 12 - 17. Though some children can and do exhibit symptoms before this age.
Sensory processing issues are common among those suffering from autism, though there is not enough research currently to know if there is any correlation.