Genetics

Genetics refers to the study of genes, different human characteristics that are influenced by genes, and also how the traits are passed down from one generation to another. Though less discussed, genetics play a significant role in human personalities and human psychology.

Genetics And Psychology

The association between genetics and psychology is a rarely discussed topic. But many researchers argue that genetics has a significant impact on the different personality traits people carry, their behavior, and also their psychology. Not only the psychological or behavioral traits but also physical appearance is highly influenced by genetics, such as eye and hair color, skin texture, height, body pattern, and many more. Research [mfn] Genetic Alliance; The New York-Mid-Atlantic Consortium for Genetic and Newborn Screening Services. Understanding Genetics: A New York, Mid-Atlantic Guide for Patients and Health Professionals. Washington (DC): Genetic Alliance; 2009 Jul 8. CHAPTER 1, GENETICS 101. Available from: https://www.ncbi.nlm.nih.gov/books/NBK115568/ [/mfn] shows that all the human traits are the result of the complex interplay between inherited genes and some environmental factors as well. However, the concept of genes influencing personality traits, psychological disposition, and behavior is extremely complex.

A 2012 research paper [mfn] Hopwood, C. J., Donnellan, M. B., Blonigen, D. M., Krueger, R. F., McGue, M., Iacono, W. G., & Burt, S. A. (2011). Genetic and environmental influences on personality trait stability and growth during the transition to adulthood: a three-wave longitudinal study. Journal of personality and social psychology, 100(3), 545–556. https://doi.org/10.1037/a0022409 [/mfn] has shown that the pathway in which genes impact psychological traits runs through the human brain – the instruction of genes is closely interlinked with brain development. When there is any difference between genetic codes, it influences the way the human brain works which results in psychological or behavioral changes.

Along with the psychological changes, genes play a pivotal role in the development of many mental health disorders [mfn] Tsuang, M. T., Bar, J. L., Stone, W. S., & Faraone, S. V. (2004). Gene-environment interactions in mental disorders. World psychiatry : official journal of the World Psychiatric Association (WPA), 3(2), 73–83. [/mfn] as well. Some people have a higher risk of developing some specific psychiatric disorders, while others don’t and the levels of risk are partly determined by genetics itself. Even the variability and severity of the mental health illness often depend on genetic differences between individuals.

Why Genetics Matter In Psychology

In the early days, many psychologists conducted numerous clinical trials to prove whether genes have an impact on human psychology or not. After several studies [mfn] Dick D. M. (2011). Gene-environment interaction in psychological traits and disorders. Annual review of clinical psychology, 7, 383–409. https://doi.org/10.1146/annurev-clinpsy-032210-104518 [/mfn], it was found that most of the human characteristics are influenced by the combination of multiple genetic and environmental factors. Genes matter in psychology for a variety of factors. There are some environmental influences also, but genes determine who an individual is inside and out. The personality and behavior that a child develops throughout his/her upbringing period largely depend on genes. There is a broad range of psychological traits influenced by genes, including:

• Social attitudes [mfn] Robinson, G. E., Fernald, R. D., & Clayton, D. F. (2008). Genes and social behavior. Science (New York, N.Y.), 322(5903), 896–900. https://doi.org/10.1126/science.1159277 [/mfn]
• Food preferences [mfn] Robino, A., Concas, M. P., Catamo, E., & Gasparini, P. (2019). A Brief Review of Genetic Approaches to the Study of Food Preferences: Current Knowledge and Future Directions. Nutrients, 11(8), 1735. https://doi.org/10.3390/nu11081735 [/mfn]
• Cognitive ability [mfn] Hill, William & Davies, Gail & Lagemaat, L & Christoforou, Andrea & Marioni, R & Fernandes, Carla & Liewald, David (Dave) & Croning, M & Payton, Antony & Craig, Leone & Whalley, Lawrence & Horan, Michael & Ollier, William & Hansell, Narelle & Martin, Nick & Montgomery, G & Steen, V & Hellard, Stéphanie & Deary, I. (2014). Human cognitive ability is influenced by genetic variation in components of postsynaptic signalling complexes assembled by NMDA receptors and MAGUK proteins. Translational psychiatry. 4. e341. 10.1038/tp.2013.114. [/mfn]
• Intelligence [mfn] Plomin, R., & von Stumm, S. (2018). The new genetics of intelligence. Nature reviews. Genetics, 19(3), 148–159. https://doi.org/10.1038/nrg.2017.104 [/mfn]
• Risk of mental illness [mfn] Geschwind, D. H., & Flint, J. (2015). Genetics and genomics of psychiatric disease. Science (New York, N.Y.), 349(6255), 1489–1494. https://doi.org/10.1126/science.aaa8954 [/mfn]
• Behavioral changes depending on age [mfn] Marteau, T. M., & Lerman, C. (2001). Genetic risk and behavioural change. BMJ (Clinical research ed.), 322(7293), 1056–1059. https://doi.org/10.1136/bmj.322.7293.1056 [/mfn]

A 2015 study [mfn] Power, R. A., & Pluess, M. (2015). Heritability estimates of the Big Five personality traits based on common genetic variants. Translational psychiatry, 5(7), e604. https://doi.org/10.1038/tp.2015.96 [/mfn] suggests that genetics also influence the big five personality traits, such as openness to new experiences, extroversion, neuroticism, conscientiousness, and agreeableness. Researchers agree that these five personality traits are influenced by heredity to some level. Genetics is extremely important to understand how a person develops a specific psychological condition. However, many psychologists also argue that genes don’t account for all the behavioral and psychological differences, but can have a substantial impact.

Read More About Extroversion Here

Defining Genetic Psychology

Genetic psychology is also known as behavioral biology. It is the field of study that explains how genes influence human behavior and personality. A 2010 research paper [mfn] Johnson, W., Turkheimer, E., Gottesman, I. I., & Bouchard, T. J., Jr (2010). Beyond Heritability: Twin Studies in Behavioral Research. Current directions in psychological science, 18(4), 217–220. https://doi.org/10.1111/j.1467-8721.2009.01639.x [/mfn] states that genetic psychologists mostly use twin and adoption studies in their research to explore how specific genes determine a person’s characteristics.

Twin studies [mfn] Sahu, M., & Prasuna, J. G. (2016). Twin Studies: A Unique Epidemiological Tool. Indian journal of community medicine : official publication of Indian Association of Preventive & Social Medicine, 41(3), 177–182. https://doi.org/10.4103/0970-0218.183593 [/mfn] help them a lot in understanding the role of heredity in personality traits mostly because monozygotic twins share common traits. If both twins develop similar traits, it indicates that the personality trait has a hereditary factor. Similarly, adoption studies [mfn] Cadoret R. J. (1995). Adoption Studies. Alcohol health and research world, 19(3), 195–200. [/mfn] explain the influence of environmental factors. It implies that children who are adopted don’t share any genetic commonalities, but the environment in which they grow up has a significant influence on their characteristics and behavioral traits. These two studies not only help genetic psychologists but also advance the understanding of how genes impact human traits.

How Genes Influence Behavior

Research [mfn] Baker L. A. (2007). THE BIOLOGY OF RELATIONSHIPS: WHAT BEHAVIORAL GENETICS TELLS US ABOUT INTERACTIONS AMONG FAMILY MEMBERS. De Paul law review, 56(3), 837–846. [/mfn] suggests that genes and behavior are closely associated with each other. Multiple genes along with some environmental factors influence behavioral changes in a person. There are some behaviors of the animal species that seem genetically predetermined. For example, cockroaches tend to revert to the dark corners of a room when the lights are on.

It is an instinctual behavior and is considered the result of evolution. Cockroaches develop this behavior as it helped their previous generations to survive. But the association between genes and human behavior is much more complex. Psychologists believe that genes don’t directly impact human behavior rather they influence certain brain functions which affect behavior.

Relation Between Genetics And Mental Illness

A 2000 research [mfn] Hyman S. E. (2000). The genetics of mental illness: implications for practice. Bulletin of the World Health Organization, 78(4), 455–463. [/mfn] has shown that genes play a significant role in developing mental illness. There are a few psychological disorders that run in families. It implies that people who have a family member with a specific mental health condition may be more likely to develop the same mental illness.

Abnormalities [mfn] MacIntyre, D. J., Blackwood, D. H., Porteous, D. J., Pickard, B. S., & Muir, W. J. (2003). Chromosomal abnormalities and mental illness. Molecular psychiatry, 8(3), 275–287. https://doi.org/10.1038/sj.mp.4001232 [/mfn] in some particular genes often lead to a variety of changes in the human brain and it leads to mental health problems in a person. The way through which those genes interact with the environment is different for every person, even for identical twins. This is the reason why an individual develops susceptibility to a specific psychological disorder.

In such instances, genes along with some significant environmental factors lead to the development of a mental illness or a psychiatric disorder. According to studies [mfn] Schmidt C. W. (2007). Environmental connections: a deeper look into mental illness. Environmental health perspectives, 115(8), A404–A410. https://doi.org/10.1289/ehp.115-a404 [/mfn], a person may develop certain symptoms of mental health disorders as a result of interaction between multiple genes and other environmental factors, including stress, loneliness, past traumatic events, or abuse which can trigger a mental illness.

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Psychiatric Disorders Caused By Genetics

The above studies have already explained that genes have a significant impact on the development of a few mental health disorders. The following are some of the psychological disorders associated with heredity:

1. Schizophrenia

A 2018 research paper [mfn] Escudero, I., & Johnstone, M. (2014). Genetics of schizophrenia. Current psychiatry reports, 16(11), 502. https://doi.org/10.1007/s11920-014-0502-8 [/mfn] suggests that genetic factors play a significant role in the development of schizophrenia. This study has also mentioned that the heritability of this disorder is between 60%-85%.

Read More About Schizophrenia Here

2. Autism Spectrum Disorder (ASD)

Researchers explain that ASD is highly genetically heterogeneous and caused by gene variations. A 2019 study [mfn] Rylaarsdam, L., & Guemez-Gamboa, A. (2019). Genetic Causes and Modifiers of Autism Spectrum Disorder. Frontiers in cellular neuroscience, 13, 385. https://doi.org/10.3389/fncel.2019.00385 [/mfn] stated that the heritability of ASD ranges from 40%-80%.

3. Attention-deficit Hyperactivity Disorder (ADHD)

Several adoption and twin studies [mfn] Faraone, S. V., & Larsson, H. (2019). Genetics of attention deficit hyperactivity disorder. Molecular psychiatry, 24(4), 562–575. https://doi.org/10.1038/s41380-018-0070-0 [/mfn] have found that ADHD runs in families. The studies have mentioned that the high heritability of this disorder is 74% which is also associated with the susceptibility of genes.

4. Major Depressive Disorder (DD)

According to many psychologists [mfn] Shadrina, M., Bondarenko, E. A., & Slominsky, P. A. (2018). Genetics Factors in Major Depression Disease. Frontiers in psychiatry, 9, 334. https://doi.org/10.3389/fpsyt.2018.00334 [/mfn], “The contribution of genetic factors to the risk of the onset of DDs is quite large.” A person who has a parent or any other family member with major depressive disorder is at greater risk of developing the same. The heritability of depression disorder is around 37%.

Read More About Major Depressive Disorder (Depression) Here

5. Bipolar Disorder

A 2014 research [mfn] Kerner B. (2014). Genetics of bipolar disorder. The application of clinical genetics, 7, 33–42. https://doi.org/10.2147/TACG.S39297 [/mfn] suggests that complex disorders like bipolar disorder are highly influenced by several genetic variants, along with some environmental factors. Rare chromosomal dysfunctions can develop such major personality disorders. According to twin studies, the heritability of bipolar disorder ranges from 60%-80%.

Read More About Bipolar Disorder Here

Takeaway

Genetics is a field of study of genes and a variety of human characteristics that are influenced by genes. Genes not only determine human personality and psychological traits but also can develop a few mental health disorders. There are also some common behavioral characteristics of the animal species that are genetically predetermined. Thus, genes play a pivotal role in human psychology and related areas.

Genetics At A Glance

1. Genes have a significant impact on the different personality traits people carry, their behavior, and also their psychology.
2. Human traits are the result of the complex interplay between inherited traits and some environmental factors as well.
3. Genes influence the big five personality traits, such as openness, extroversion, neuroticism, conscientiousness, and agreeableness.
4. There are some mental health disorders associated with genetics, including bipolar disorder, ADHD, ASD, depressive disorder, and schizophrenia.
5. Genes along with some environmental factors, such as traumatic events, stress, and abuse can contribute to the development of mental illness.