Misophonia: Part One. A hatred of human sounds.

It is common to come across an individual, or even notice about yourself that upon hearing human sounds such as chewing, breathing and swallowing, an emotional aversion or annoyance is provoked emotionally. Sensitivity to sounds diverges has been classified into many distinguished conditions. Jastreboff and Jastreboff, 2002 first noted and introduced the term Misophonia [1]. Misophonia is a condition where individuals experience a dislike and negative reaction to particular sounds. Emotional reactions are unique to each Misophonic individual and the cause and severity are dependent on how the sound was first experienced.

Hyperacusis is a condition where an individual is particularly sensitive to sounds and this has been frequently found to coexist with Misophonia, differentiated by its sensitivity to the subjective response provoked. Because of this, it is difficult to differentiate Hyperacusis, Misophonia and mixed comorbidity, problematic when trying to diagnose and target treatment. Jastreboff and Jastreboff, 2002 suggest that 60% of Tinnitus patients also have Misophonia and 86% of tinnitus patients have hyperacusis. Another subtype of Misophonia is Phonophobia, a fear of loud sounds or certain sounds where the response evoked is causing mainly fear, which also notes high rates of comorbidity [1].

But how common is this condition, and it is a significant clinical burden? Wu et al, 2014 using a student population of 483 undergraduates (mean age: 21.4 years) investigated incidence, correlates and impairments associated with Misophonia [2]. This study found that 22.8% of students were often or always sensitive/annoyed by specific sounds (e.g. human sounds). Additionally, specific sounds such dislike of throat sounds, rustling papers and environmental sounds were reported by 19.5, 16.1 and 14% of students respectively [2].

How are these aversions to sound conditions classified? Research has disputed the boundaries of emotional responses and the dominant emotional reaction that differentiates these conditions. Rouw and Erfanian, 2018 suggest that there are at least 4 different dominant emotions rather than anger in Misophonia [3]. These emotions are stress, anxiety, impatience and irritation. In some cases, Misophonia can evoke physical reactions. Moller, 2011 founds that some patients reported physical pressure building in the chest, desire to stop the person producing the sound and other autonomic reactions in addition to emotional reactions [4]. Sufferers may always be in a state of a perpetual state of anxiety as they are always conscious about when a trigger sound may be heard. Individuals of Misophonia can reduce the quality of life due to the debilitating physical and emotional suffering, hyper-focusing on trigger sounds, avoidance of situations and interference of completing day to day tasks without irritational thoughts.

Jastreboff and Jastreboff, 2014 [5] found that only 7 cases (2.2%) out of 318 Misophonic patients exhibited a psychiatric disorder. Some researchers argue that Misophonia and psychiatric disorders are unrelated whereas others suggest that they can coexist. Studies showed a pattern of intense reactions to specific stimuli and avoidance that matched with traits of other psychiatric disorders such as post-traumatic stress disorder, autism, and sensory processing disorders.

Many of these symptoms are emotionally based, therefore is hard to diagnose as most diagnosis methods require tangible evidence. So, the question is what, if any, biological abnormality occurs in a Misophonic sufferer and an unaffected individual? Loudness Discomfort Levels (LDL) in decibels (dB) in a study by Jastreboff and Jastreboff, 2014 [5] found that when Misophonia is present with hyperacusis, LDL values range from 30 to 120 dB. When deviant sound is heard, a study by Schroder et al., 2014 [6] found a reduced N1 peak in Auditory Evoked Potentials (AEP, see Figure) in Misophonia patients than in healthy controls.

Auditory Evoked Potentials: When neurons fire, they produce electrical action potentials. When auditory stimuli are heard, a pattern of alternating voltages occurs in the brain. An Auditory Evoked Potential (See A) lasting around half a second can be visualised in waveform by recording electrodes from an electroencephalogram over the cortex responsible for auditory information processing. There are phases of the AEP – P1, N1 and P2. The waveform nomenclature is determined by using capital letters stating whether the peak is positive (P) or negative (N) followed by a number which indicates the average latency for that wave. For example, P1 is a wave with a positive peak at approximately 1 millisecond following stimulus onset. (B) shows the difference of the AEP in Misophonic individuals and an unaffected control. Note, a defining characteristic noted by Schroder et al., 2014 is the reduced peak of the negative N1 wave. For more information about Auditory Evoked Potentials, visit: https://link.springer.com/referenceworkentry/10.1007%2F978-3-540-29678-2_433 Source: (A) Purdy, Suzanne & Kelly, Andrea & Thorne, Peter. (2001). Auditory Evoked Potentials as Measures of Plasticity in Humans. Audiology & neuro-otology. 6. 211-5. 10.1159/000046835. (B) Schroder A, van Diepen R, Mazaheri A, Petropoulos-Petalas D, Soto de Amesti V, Vulink N, et al. Diminished N1 Auditory Evoked Potentials to Oddball Stimuli in Misophonia Patients. Frontiers in Behavioral Neuroscience. 2014 Apr 9;8.

‌Misophonia is a complex and currently is very limited in the understanding of its neurological basis. In the next article, we will further explore another aspect of the cognitive neuroscientific basis of Misophonia, the availability of treatment, and the prospects of future research.

For more information from scientific articles, please read:

[1] Jastreboff PJ. Tinnitus Retraining Therapy. Textbook of Tinnitus [Internet]. 2011 [cited 2019 Nov 16];575–96. Available from: https://link.springer.com/chapter/10.1007%2F978-1-60761-145-5_73

[2] Wu MS, Lewin AB, Murphy TK, Storch EA. Misophonia: Incidence, Phenomenology, and Clinical Correlates in an Undergraduate Student Sample. Journal of Clinical Psychology. 2014 Apr 17;70(10):994–1007.

[3] Erfanian M, Rouw R. EMOTIONAL AND COGNITIVE CHARACTERISTICS OF MISOPHONIA. European Neuropsychopharmacology. 2018 Jun;28(6):780–1.

[4] Møller AR, Al E. Textbook of tinnitus. New York: Springer; 2011.

[5] Jastreboff M, Jastreboff P. Treatments for Decreased Sound Tolerance (Hyperacusis and Misophonia). Seminars in Hearing. 2014 Apr 29;35(02):105–20.

[6[ Schröder A, Vulink N, Denys D. Misophonia: Diagnostic Criteria for a New Psychiatric Disorder. Fontenelle L, editor. PLoS ONE [Internet]. 2013 Jan 23 [cited 2019 Nov 16];8(1):e54706. Available from: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0054706

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