The Role of Biology on Mental Illness

by Aleksandra Hurka

Psychology Department, Lake Tahoe Community College

PSY210-01: Introduction to Biological Psychology

Professor Gina Curasi

August 10, 2025

Effect of Heredity on Mental Illnesses

Out of the many mental health disorders people all over the world face, there are certain ones that have a higher heritability rate than others. For example, illnesses like schizophrenia and bipolar disorder are known to have a 70-90% heritability rate (Ganesh et al., 2019). These disorders are caused by mutations in mendelian genes. 47.6% of variants containing genes were reported to contribute to the risk of neuropsychiatric syndromes, while 21.4% of that were caused by mendelian inheritance (Ganesh et al., 2019). This suggests there is a pattern to inheritance for these diseases that isn’t caused by the environment, but rather a deleterious mutation and these genes encode proteins responsible for neuronal development. Additionally, there is evidence showing that 10 other genes contribute to polygenic syndromes such as PTSD, ADHD, and Parkinson’s (Ganesh et al., 2019). This evidence shows that aside from neuropsychotic syndromes, neuronal alpha-synuclein diseases like Parkinson’s are genetically linked. While there are certain disorders that are more heritable than others like anxiety and depression, studies show there is evidence to some level of heritability for these disorders. In a twin study surveying monozygotic and dizygotic twins ages 3-12, it was found that heritability for anxiety and depression decreased as the children grew older (Boomsma et al., 2005). Since heritability decreased with age, this implies that the environment had influence on the children’s behavior at a certain point in time. Additionally, since both parents were rating how likely they felt these disorders were present due to heritability and there were some disparities in the ratings, this demonstrates how shifting relationships between parent and child could contribute to the development of these disorders. There is also evidence of the 5-HT1AR gene contributing to anxiety and depression in mice. If this gene is activated during the prenatal period, the mouse will develop anxiety-like behavior into adulthood, whereas if it were not activation, the mouse would experience behavioral inhibition (Boomsma et al., 2005). While anxiety and depression aren’t as heritable as schizophrenia and depend on some level of environmental influence, there is evidence that genes such as 5-HT1AR are contributors to these mental illnesses.

Effect of Environment on Mental Illnesses

While certain heritable factors can contribute to the development of mental diseases, the environment also plays a role in the acquisition of them. In a study done to survey the mental health status of physical therapists based on their working environment, it was found that mental health problems arose due to fragmented tasks, lack of resources and social support in comparison to the decrease in mental health issues when work felt meaningful (Hagen et al., 2025). This implies that work engagement significantly rose when work felt purposeful, suggesting a lack of purpose might be contributing to the listed environmental variables involved in mental health issues the therapists face. It was also reported that older therapists felt there was less opportunity to use their knowledge and potential in the workplace, causing them to experience a lack of social support unlike their younger coworkers (Hagen et al., 2025). The difference in treatment of different generations suggests age might be a factor in affecting workplace compliance, considering the varying education level that may have been received by each generation.

Protective Factors Against Heritable Mental Illnesses

Even though some mental illnesses may have a higher likelihood than others of getting passed down, there are certain measures individuals are able to take to prevent the chances of acquiring disorders. In a study done to evaluate the success of different interventional treatment for families struggling with dysfunction due to the parents’ mental health status, it was found that “family-group cognitive-behavioral intervention” significantly improved the behavior of a child who has a parent struggling with a disorder (Gjøde et al., 2025). This strategy of personalized intervention and therapy for the entire family may be significant in preventing the acquisition of mental illnesses for the child in the future, considering that building cooperative and non aggressive habits could be a foundation for mental stability.

Opinions and Recommendations

This research experience has enlightened me in many ways about how both heritability and environment play a role in the acquisition of mental disorders. However, prior to my research, I believed that if an illness were to run in the family then it would be inevitable for an offspring to inherit it. Through my research, I was able to find out preventive methods to delay the onset of illnesses and different therapeutic methods to combat that. I do believe that even people with a high probability of getting an illness passed down to them have ways to protect themselves. Family therapy or having access to social services could be beneficial for someone seeking relief from an environment where they could be easily affected by the behaviors of their parents with a mental disorder. Some environmental variables that people with a high probability pass down rate should be mindful of is having a safe, and personalized space for themselves that could help them destress in stressful situations. Having a good support system from friends or other relatives is crucial so that if a person needs to talk about what is going on in the family home then they are able to. On the other hand, based on the diathesis stress model, a person’s environment may enhance or reduce their likelihood of obtaining a mental disorder if they have a high probability of being passed down to them. In an environment that has less triggers for people that may be at risk for mental disorders, that decreases stress that may contribute to the acquisition of a disorder. However, an environment with lots of stressors such as poor social support, lack of communication, and aggressive behavior could lead to the eventual development of the disease, considering a person is surrounding themselves in a triggering environment.

References

Boomsma, D. I., Van Beijsterveldt, C. E. M., & Hudziak, J. J. (2005). Genetic and environmental influences on anxious/depression during childhood: A study from the Netherlands twin register. Genes, Brain & Behavior, 4(8), 466-481. https://doi.org/10.1111/j.1601-183X.2005.00141.x

Ganesh, S., Ahmed P, H., Nadella, R. K., More, R. P., Seshadri, M., Viswanath, B., Rao, M., Jain, S., Mukherjee, O., Rao, N. P., Narayanaswamy, J. C., Sivakumar, P. T., Kandaswamy, A., Kesavan, M., Mehta, U., Venkatasubramanian, G., John, J. P., Purushottam, M., Kannan, R., & Mehta, B. (2019). Exome sequencing in families with severe mental illness identifies novel and rare variants in genes implicated in mendelian neuropsychiatric syndromes. Psychiatry & Clinical Neurosciences, 73(1), 11-19. https://doi.org/10.1111/pcn.12788

Gjøde, I. C. T., Müller, A. D., Hjorthøj, C., Hemager, N., Ingversen, S., Moszkowicz, M., Christensen, S. H., Mikkelsen, L. J., Nielsen, S. S., Melau, M., Forman, J., Nordentoft, M., & Thorup, A. A. E. (2025). Effects on family functioning and the home environment of a family-based preventive intervention for children of parents with severe mental illness: A randomized controlled trial. Journal of Consulting and Clinical Psychology, 93(4), 267-280. https://doi.org/10.1037/ccp0000924

Hagen, S., Bergheim, L. T. J., & Torp, S. (2025, March 1). "Exploring job demands and resources influencing mental health and work engagement among physical therapists: A cross-sectional survey of Norwegian physical therapists.." (0959-3985). Taylor & Francis. https://doi.org/10.1080/09593985.2024.2348731