By Satya Mouktika
(Image from BBC Science Focus)
A study by doctors in 1987 investigated how Post Traumatic Stress Disorder (PTSD) affects monozygotic (have identical DNA) and dizygotic (their DNA slightly differs from one another ) twins. They surveyed and observed 4029 male twins of the US military during the Vietnam War. Their findings showed that monozygotic twins have a more similar susceptibility to trauma than dizygotic twins. This posed the question- do our genes have a control over our mental health? And if so, how much control do they have?
So, the short answer to that question is yes- genes do have a control over one's mental health. But it is far more complex than that.
Gene Expression and Risk Genes
Every human has 46 chromosomes (23 pairs) and 1 chromosome from each parent in a pair. The DNA is found in these chromosomes and the instructions in the DNA to code for a protein is called a ‘transcript.’ The collection of all the transcripts is called the ‘transcriptome.’ This only focuses on the parts of the genetic code that are expressed.
Depression, bipolar disorder and schizophrenia are all linked back to variation in 2 genes in the third chromosome. This raises a question- if all three have the same genetic roots, how are they so different from each other? To answer this question, researchers studied the transcriptomes from patients with these 3 disorders. After comparing them, they had found slight differences in the parts of the genes that are ‘turned on’ or ‘kept off.’ These genes were then identified as ‘risk genes.’
A table showing how the probability of being diagnosed depends on one’s family background
Environmental factors
Genes do play a major role in the mental health of a person, but so does the environment. Even if a person has no genetic predisposition to any major mental illness, factors such as; traumatic life events, lack of nutrients, family stress and social disadvantage are still risk factors of Major Depression Disorder and extreme anxiety. Although this has been an ongoing debate for decades in both genetics and psychology, the common conclusion is that both genetics and environmental factors influence mental health outcomes.
Sources
Eisen, S., True, W., Goldberg, J., Henderson, W., Robinette, C., Neuman, R., Rice, J., Henderson, W. ;, Barnes, J., & Vitek, M. (1987). Determining Zygosity in the Vietnam Era Twin Registry -An Approach Using Questionnaires. Acta Geneticae Medicae et Gemellologiae, 36(1), 368–373. https://doi.org/10.1002/ajmg.1320480107
Akula. N., Marenco, S., Johnson, K., Feng, N., Zhu, K., Schulmann, A., Corona, W., Jiang, X., Cross, J., England, B., Nathan, A., Detera-Wadleigh, S., Xu, Q., Auluck, P. K., An, K,. Kramer, R., Apud, J., Harris, B. T., Rhodes, C. H., Lipska, B. K., McMahon, F. J. (2021). Deep transcriptome sequencing of subgenual anterior cingulate cortex reveals cross-diagnostic and diagnosis-specific RNA expression changes in major psychiatric disorders . Neuropsychopharmacology
Common Genetic Factors Found in 5 Mental Disorders. (2015, May 12). National Institutes of Health (NIH). https://www.nih.gov/news-events/nih-research-matters/common-genetic-factors-found-5-mental-disorders#:~:text=The%20suspect%20region%20along%20chromosome
Does mental illness run in families? (n.d.). Does Mental Illness Run in Families? https://www.rethink.org/advice-and-information/carers-hub/does-mental-illness-run-in-families (Table)