How You Were Born

By Matt Odoyle

Introduction

Studies have shown that 50 percent of our happiness is determined prior to birth. [^1] Genetics contribute to happiness by coding for the creation, destruction, and transportation of biological molecules that influence mood. Additionally, genetics code for attributes associated with happiness, such as personality. By analyzing the relation between happiness and three paradigmatic traits determined by genetics – a neuro-protein, a serotonin transporter, and personality – one can gain intuition about the influence of genetics on happiness. Brain-derived neurotrophic factor

Brain-derived neurotrophic factor, or BDNF, is a secreted protein that has survival and growth promoting effects on neurons. BDNF has been implicated in a variety of neural functions, including neurogenesis and memory.[^2] Studies have also linked BDNF levels to mood.[^3]

BDNF’s association with mood has been investigated by analyzing BDNF levels in relation to environmental stressors that have been shown to induce depression. The research showed that BDNF mRNA expression was negatively correlated with the environmental stressors.[^4] Conversely, antidepressants increase BDNF mRNA expression in the brain. [^5]

BDNF has also been linked to mood by a single nucleotide polymorphism (or variation in one location of a gene), rs6265, which has been associated with depression.[⁶] A study of individuals with major depression revealed that those with two copies of the major allele GG were more likely to be depressed.[^7]

BDNF plays a large role in influencing mood. BDNF levels are influenced by environmental stressors linked to depression, and one BDNF variation is linked to depression.

Serotonin

Serotonin (5-hydroxytryptamine) is a neurotransmitter with strong connections to mood. This relationship has been targeted by medications to treat depression, such as selective serotonin re-uptake inhibitors and monoamine oxidase inhibitors, which treat depression by increasing levels of extracellular serotonin in the brain. In addition to serotonin itself, variations of the serotonin transporter are linked to an individual’s happiness.[^8]

Coding for a serotonin transporter, a single nucleotide polymorphism in a gene called 5-HTTLPR has been implicated in moderating the effect of stressful life events on well-being.^[9] There are two basic variations of the gene, long and short alleles. Individuals with one or two copies of the short allele exhibit more depressive symptoms and diagnosable depression in association with stressful events than individuals with two copies of the long allele.^{[10], [11]}

Personality

Research indicates that genetic differences in subjective well-being are associated with genetic components for neuroticism, extraversion, and conscientiousness.^[14] The five-factor model of personality, which asserts that openness, conscientiousness, extraversion, agreeableness, and neuroticism are the five major domains of personality, has been shown to have a large genetic component.

Research has consistently determined that these five domains have a heritability of 40 percent.^{[12], [13]} A common genetic factor that affects all five of the personality domains has also been implicated in affecting well-being, establishing a direct link between the innate personality traits and happiness.^[15]

Conclusion

Genetics is responsible for half of an individual’s happiness. The levels of many biological molecules that are linked to happiness, such as neurotransmitters and neuro-proteins, are mediated by genetics. In a different vein, innate personality traits, which contribute to 40 percent of what comprises human personality, are strongly associated with well-being. This information reinforces the notion that genetics contributes to a base level of happiness; however, it also shows that happiness cannot fully be attributed to genetics. The remainder of happiness is determined by situation and the outlook of the individual.

 Bibliography

• [1] Lyubomirsky, S. (2008). The how of happiness: A scientific approach to getting the life you want. New York: Penguin Press. 
• [2] BINDER, DEVIN K., and HELEN E. SCHARFMAN. "Brain-derived Neurotrophic Factor." Growth Factors 22 (2004): 123–131. PubMed. Web. 5 Feb. 2012.
• [3] Ibid.
• [4] Ibid.
• [5] Ibid.
• [6] Ribeiro, Luciana , João V. Busnello, Rita M. Cantor, Fiona Whelan, Pamela Whittaker, Panos Deloukas, Ma-Li Wong, and Julio Licinio. "The brain-derived neurotrophic factor rs6265 (Val66Met) polymorphism and depression in Mexican-Americans." Neuroreport 18 (2007): 1291-1293. PubMed. Web. 11 Feb. 2012.
• [7] Altar, CA. "Neurotrophins and depression." Trends Pharmacol Sci. 20 (1999): 59-61. PubMed. Web. 12 Feb. 2012.
• [8] Caspi, A, K Sugden , R Poulton , TE Moffitt , A, Taylor , IW Craig , H Harrington , J McClay, J Mill, J Martin, and A Braithwaite. "Influence of life stress on depression: moderation by a polymorphism in the 5-HTT gene." Science 5631 (2003): 386-9. PubMed. Web. 10 Feb. 2012.
• [9] Ibid.
• [10] Ibid.
• [11] K., Karg, Burmeister M, M., Shedden K., and Sen S.. "The serotonin transporter promoter variant (5-HTTLPR), stress, and depression meta-analysis revisited: evidence of genetic moderation.." Arch Gen Psychiatry 68 (2011): 444-54. Print. 2012.