How is "Irritable Temperament" encoded by the genome?
Do you think of yourself as generally irritable? For example, do you often get in heated arguments, tend to get violent with alcohol, or can be cross if you are tired. Lack of sleep, stress overload, low blood sugar levels, and hormonal changes can be causes of irritability. Irritable temperament is one of the five domains of affective temperament, along with depressive, hyperthymic, cyclothymic, and anxious. Irritability is a common state of mood. However, severe chronic irritability may be described as a symptom of some psychiatric disorders such as addiction and post-traumatic stress disorder (PTSD). In general, many of these temperaments or conditions are thought to have a strong biological background, manifesting at an early age and persisting through the lifespan.
Previous research indicated genetic associations and strong heritability, more marked manifestation not only in affective disorder patients but also in their first-degree relatives. Because of the distribution throughout the population and the several outcomes of affective illness and general illness course, genome wide association studies (GWASs) could bring us closer to the identification of genes in depression. Yet, previously, no whole genome wide analysis was performed for affective temperaments in a general population sample, and there has been only one GWAS in a bipolar patient sample.
Researchers performed a pilot GWAS on five affective temperaments in a European general population sample in this context. This study was part of the NewMood project, a collaboration between 13 clinical and basic science research groups across 10 European countries aimed at identifying new molecules in the background of mood disorders. Phenotypic and genotypic data from 775 participants in the Budapest cohort, of which participants were recruited via advertisements, general practices, and a website, were used for the GWAS. Participants filled out the NewMood questionnaire pack, including the standardized Hungarian version of the 110-item Temperament Evaluation of Memphis, Pisa, Paris, and San Diego (TEMPS-A) questionnaire to measure five affective temperaments. The TEMPS-A consists of five scales measuring the five affective temperaments (irritable, depressive, hyperthymic, cyclothymic, and anxious). As for irritable temperament, participants were asked to answer yes or no to the questions such as “I can get so furious I could hurt someone”, “ I often get so mad that I will just trash everything” and “When crossed I could get into a fight”. Each affective temperament score was calculated as a continuous weighted score by dividing the sum of item scores by the number of completed items. Results showed that variant rs2969184 in the SHISA6 gene on chromosome 17 was related to irritable temperament with suggestive significance. This is significant because this gene is involved with the systems that are involved in preventing synaptic depression and desensitization. Variation in the SHISA6 gene in GWASs has been implicated in risk-taking behavior/adventurousness, insomnia, and sleep duration.
However, a major limitation of this study could be the sample size sample size. Read more about the study here:
https://pubmed.ncbi.nlm.nih.gov/34075027/
Are you interested in learning more about your genetic tendency for irritable temperament? You can login to your Genomelink YOUR TRAITS to see this new genetic trait.
