April 2023
Misophonia is a disorder that has gained more attention in recent years. It is marked by an intense emotional response to certain sounds, like chewing or breathing, that can cause a lot of distress and affect a person’s daily life. Although the causes of misophonia are not agreed upon, scientists are trying to learn more about how genetics may play a role.
A new study, conducted by researchers at the University of Amsterdam Medical Center and published in Frontiers in Neuroscience, investigates the genetic causes of misophonia. The study seeks to investigate misophonia by looking at the genetic and neurobiological factors that contribute to its development. The researchers used a genome-wide association study (GWAS) to identify genetic markers associated with misophonia.
Before discussing the findings of this study, it is important to provide some general information about the structure of cells, chromosomes, DNA, and genes, as well as their relationships.
Cells are the basic units of life, and they come in many different shapes and sizes. They are the building blocks of all living organisms, from the smallest bacteria to the largest animals. Cells are responsible for carrying out all the functions necessary to sustain life, including energy production, metabolism, and reproduction. Within cells, there are several important structures, including the nucleus, which contains the cell’s genetic material. The nucleus is a membrane-bound organelle that houses the cell’s DNA. DNA, or deoxyribonucleic acid, is a molecule that carries the genetic information necessary for the development and function of all living organisms.
The DNA in the nucleus is organized into structures called chromosomes. Chromosomes are long, coiled-up strands of DNA that contain many genes. Genes are the basic units of heredity, responsible for encoding the information necessary for the production of proteins and other molecules necessary for the functioning of cells and organisms. When two genes are close to each other on the same chromosome, they are said to be linked. This means that these genes are physically located near each other on the chromosome, and they tend to be inherited together as a unit during cell division and reproduction.
In more detail, DNA is made up of four different nucleotide bases – adenine, guanine, cytosine, and thymine (presented in four different colors of blue, green, orange and red in the figure) – that are arranged in a particular sequence. This sequence of nucleotides determines the information encoded in the DNA, which in turn determines the structure and function of proteins and other molecules that are necessary for the functioning of cells and organisms.
Chromosomes are structures that help to organize and package DNA in cells. Humans have 23 pairs of chromosomes, for a total of 46 chromosomes. Each chromosome contains many genes, and the arrangement and number of chromosomes can vary between different species.
Figure 1. The image demonstrates the structure of cell including a nucleus. Cell nucleus contains 46 chromosomes (23 pairs). Each chromosome has a long molecule of DNA and DNA includes of lots of genes.
In the study conducted at the University of Amsterdam Medical Center, the researchers analyzed a GWAS of common misophonia symptoms such as irrational anger, irritation, and disgust directed towards the person making the sounds, increased heart rate, and physical avoidance of the stimuli, in a general population-based sample from 23andMe.
They looked at the genes that might cause misophonia. Their goal was to find out which genes play a role in causing misophonia and to learn more about how the disorder affects people differently.
What is a genetic correlation?
When we say that the gene associated with disorder A is correlated to genes in disorder B, it means that there is a relationship or association between the two disorders at a genetic level. This suggests that there might be a shared genetic component between the two disorders, which could explain why some individuals may be susceptible to both conditions.
The research found that there is a relationship between the genes that cause misophonia and tinnitus, a condition that causes ringing in the ears. This supports previous neuroimaging and behavioral studies that suggest that misophonia symptoms are similar to but not the same as tinnitus, hyperacusis (sensitivity to sound), and phonophobia (fear of sound). Misophonia did not correlate with any hearing performance or hearing loss traits, which is in contrast to tinnitus that based on past studies is weakly but significantly correlated with severity of hearing loss. For more information about the relationship between severity of hearing loss and tinnitus loudness see this research-based video explaining the outcome of studies conducted at Hashir International Specialist Clinics and Research Institute for Misophonia, Tinnitus & Hyperacusis.
The study also found significant genetic correlations between misophonia and several other disorders and behavioral traits, including PTSD, major depressive disorder, generalized anxiety, and various personality traits. These findings are consistent with previous research on comorbidities of misophonia with psychiatric disorders and correlations with symptoms and personality traits.
No significant correlation was found with anorexia or obsessive-compulsive disorder (OCD), which is in contrast to previous studies that reported a link. The study suggests that they are not the same condition, and may have distinct underlying causes, symptoms, and treatment approaches.
The study found that there is a negative correlation between misophonia and Autism Spectrum Disorder (ASD), which goes against the team’s previous research and the findings of ASD experts. In other words, the results of this study suggest that misophonia and ASD are less likely to occur together than what was previously thought. The emotional response that defines misophonia may also be found in patients with ASD, but this is not reflected in an overlap in genomic variation. The study suggests that misophonia and ASD are relatively independent disorders with regard to genomic variation. On the other hand, patients in the ASD group in the current study did not necessarily present with misophonia symptoms hence a strong relationship with misophonia in genomic variation is not expected (i.e., not all patients with ASD have symptoms similar to misophonia). Future studies should compare genomic variation between patients with ASD who also present with misophonia symptoms compared to patients with misophonia with ASD. Such results can shed some light on whether misophonia symptoms among ASD population are related to comorbid misophonia or only to their underlying ASD.
Previous studies suggest that personality traits and past negative experiences are likely to lead to misophonia. This can create a cycle where the body’s physical and emotional responses to trigger sounds become stronger over time. In line with past findings, this study found that there is a genetic connection between misophonia and various psychiatric disorders such as posttraumatic stress disorder (PTSD), major depressive disorder (MDD), and generalized anxiety (GAD) and traits including being easily annoyed or anxious.
The study also found that the correlation with aggression was not significant, which is unexpected given that anger and aggressive thoughts are often reported symptoms of misophonia. Although findings in this regarding are inconsistent (See our previous post), this could be explained in light of previous studies looking at the brain basis symptoms of misophonia which suggest that misophonia is more compulsive and internalizing than impulsive and externalizing in character. Compulsive behaviors refer to repetitive actions that an individual feels compelled to do, even if they do not want to or understand why they are doing it (e.g., mimicking the trigger). Internalizing emotions refers to keeping emotions inside rather than expressing them outwardly. This can include feelings of anxiety, depression, and self-doubt. On the other hand, impulsive behaviors refer to acting without thinking about the consequences, while externalizing emotions refer to expressing emotions outwardly, such as anger, aggression, or hyperactivity.
The results of this study could help guide future research into the genetic and neurobiological factors involved in misophonia, as well as potential pharmacological or neuromodulatory treatments. For example, if a genetic study identifies a gene that is associated with depression, researchers can investigate whether drugs that target that gene or the pathway it is involved in could be effective in treating the disorder. Additionally, genetic studies can help identify patient subgroups who may be more likely to benefit from a particular treatment, allowing for more personalized and effective treatment strategies.
Furthermore, genetic studies can help identify potential side effects of certain treatments or drugs by revealing how they might affect other genes or pathways in the body. This information can be used to design safer and more effective treatments.
However, further research is needed to fully understand the complex interactions between genetic, neural, and contextual factors that contribute to misophonia. While the study provides important insights into the genetic basis of misophonia and its relationship with other disorders, it acknowledges that methodological issues remain, and more sensitive measures of hearing sensitivity and other sensory problems than hearing loss may reveal a relationship between misophonia and other disorders. Future studies may also investigate the specifics of the relation between misophonia and ASD, aggression, anorexia, and OCD. In addition, genetic studies can be expensive and require a lot of genetic information from a large group of people (N >1000) who have been diagnosed with misophonia. Such a database is not currently available. In this study, the researchers looked at genes that are related to emotional characteristics and other disorders that often occur alongside misophonia, rather than directly looking at the genes related to misophonia itself.
What to do if you have misophonia?
Misophonia is a real and highly debilitating disorder that can have a significant impact on individuals’ lives, and it can be challenging to manage without support. If you or someone you know is struggling with misophonia, it is essential to seek help from healthcare professionals who understand the disorder and can provide effective treatment options.
This review is written by Dr Mercede Erfanian PhD who is a research fellow at Hashir International Specialist Clinics and Research Institute for Misophonia, Tinnitus & Hyperacusis.
