By: Eshita Chahal
Genes, chromosomes, DNA, and so on are just a few of the many factors that contribute to us being human. Genes that are passed down through generations and sometimes minutely altered (genetic mutation), can influence physical appearance, personality, biological makeup, and even mental health. Some people are unusually tall because it runs in the family, while others have specific eye colors, but no one mentions genetically inherited mental disorders. Just as not everyone inherits diseases from their family, not everyone inherits a mental illness, but the possibility cannot be ruled out. After all, genes play an important role in determining a person's risk of developing a disease or condition.
Although there are common gene variants associated with mental disorders, no gene variant can predict a person's likelihood of developing a disorder with certainty. “Well, we can just check if we are at risk for a mental disorder,” one might think, however, due to the numerous variants and overlapping mental disorder symptoms, it is extremely difficult to pinpoint the chances, because even if they are identified, there is no guarantee that they will affect the person because genes raise the risk by a very small chance. No mental disorder has a one-hundred percent heritability risk, and other factors, such as environmental factors, may have a strong influence on whether or not a person develops a particular disorder, regardless of the presence or absence of genetic factors. Nevertheless, let us look at those that have been found to be heritable, as well as some gene variants in those disorders.
While environmental factors play a significant role in the development of a bipolar disorder, genetic factors are considered to account for 70-90% of all cases. Anxiety disorders, PTSD, OCD, and major depressive disorder are inherited in approximately 20-45% of cases, whereas alcohol dependence and anorexia nervosa are inherited in 50-60% of cases, and bipolar disorder, autism spectrum disorders, schizophrenia, and ADHD are inherited in approximately 75% of cases. The Genome-Wide Associated Studies (GWAS), which identified some of the many genetic variants that can be linked to mental disorders, are responsible for many of the findings in these statistics.
So, what is the link between them? A bunch of specific genetic mutations or polymorphisms (SNPs) within CACNA1C, ODZ4, TRANK1, GNG2, ANK3, TPH2, ITPR2, SHANK2, & NCAN but namely, CACNA1C. CACNA1C gene variation had previously been linked to bipolar disorder, schizophrenia, and major depression. CACNA1C has been shown to affect brain circuitry involved in emotion, thought, attention, and memory — all of which can be disrupted in mental illnesses. Variations in another calcium channel gene, CACNB2, were also linked to the five disorders. Subsequently, CACNA1E/B2 were also considered strong candidates for Autistic Spectrum Disorder (ASD).
These may appear to be a collection of random alphabets strung together in an incomprehensible manner, but each of these has taken years of research to discover small links to help humanity be aware of any risks they may pose. Mental disorders such as bipolar disorder, schizophrenia, and autism spectrum disorder (ASD) have strong genetic bases that can be inherited directly from an affected parent or start anew during development when combined with environmental factors. However, just because there is a chance does not mean that a person with a family history of mental disorders will be affected by or develop said mental disorder as well. Although statistically insignificant, each of these genetic associations can only account for a small amount of risk for a mental illness, the findings may aid researchers in making more accurate diagnoses in the near future. They would also help us better understand the factors and causes that can lead to mental illness. The start may be late, and the results may be minimal, but current progress will pave the way for a better and more precise diagnosis, leading to a better understanding of the human mind.
References:
“Common Genetic Factors Found in 5 Mental Disorders.” National Institutes of Health, U.S. Department of Health and Human Services, 15 May 2015, www.nih.gov/news-events/nih-research-matters/common-genetic-factors-found-5-mental-disorders.
“Genetics and Mental Illness.” Psychology Today, Sussex Publishers, www.psychologytoday.com/us/blog/evolutionary-psychiatry/201909/genetics-and-mental-illness.
“Looking at My Genes: What Can They Tell Me About My Mental Health?” National Institute of Mental Health, U.S. Department of Health and Human Services, www.nimh.nih.gov/health/publications/looking-at-my-genes/.
Shabir, Dr. Osman. “The Genetics of Mental Disorder.” News, 22 Mar. 2021, www.news-medical.net/health/The-Genetics-of-Mental-Disorder.aspx.
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