GENES INVOLVED IN BOTH DOPAMINERGIC AND

SEROTONERGIC PATHWAYS AND FINANCIAL DECISION

MAKING

Dr. Sc. Sezen GÜNGÖR

Tekirdağ Namık Kemal University, Çorlu Vocational School, dr.sezengungor@gmail.com

Article history:

Accepted 18 July 2019

Available online 23 August 2019

Keywords:

Genoeconomics,

Financial Decision,

Dopamine,

Serotonin,

MAOA gene

A b s t r a c t

One of the most important assumption of rational choice theory is that individuals are purely self-

interested utility maximizers. However research in economics and other social sciences has found

that people can also be irrational and their choices can also be taken with some heuristics and biases.

Laboratory experiments have documented substantial heterogeneity in irrational preferences, but

little is known about the origins of such irrational financial behavior. Especially in recent studies, it

is seen that the inheritance estimates of these differences are investigated by using quantitative and

molecular genetic methods.

The main purpose of this study is to investigate the effects of dopamine and serotonin-related genes

on financial decisions. For this purpose, genes associated with dopamine and serotonin were

identified. Some of the studies investigating the effects of these genes on financial decision making

process have been examined.

Introduction

The biological basis of financial decisions and heuristics or

biases, such as reward dependence, loss aversion, is not yet fully

understood. However, the anatomy of choice and financial

decisions has been well-studied.

In particular, studies on decision making are handled together

with psychology, neurology and genetic sciences. The

experimental background of these studies consists of personality

tests in psychology, brain imaging techniques in neurology and

genes, hormones and neurotransmitters in genetics.

The current studies from neurofinance, neuroeconomics,

psychology and of course neuroscience discussed about three

decision-making systems in the human brain, and dopamine and

serotonin is the principal neurotransmitter that is involved in these

three systems (Wargo, Baglini and Nelson, 2010):

1. An unconscious, intuitive and emotional system,

2. A conscious, rational system or executive function,

3. A system of habitual behavior that is either

preprogrammed genetically or developed into habits over time.

Limbic system - the emotional center of the brain – is about some

behaviors and some biases in financial decisions such as

reward/approach, loss/avoidance, investment behavior or novelty

seeking (Knutson & Cooper, 2005; Taylor, 2006). Any problems

in this system can make you more willing to take risks, greed or

dependence.

The effects of genes are not expressed directly at the level of

behavior, but are mediated by their effects on brain regions

responsible for specific cognitive and emotional processes (Bigos

and Weinberger, 2010). On the other hand, hormones and

neurotransmitters can have an effect on behaviors by changing an

individual´s phenotype (Soares et al., 2010), moreover these

behaviors can also be influenced by genetic and epigenetic

differences (Liu et al., 1997; Meaney, 2001). Empirical findings

from genoeconomics and neuroeconomics (Benjamin et al., 2007;

Beauchamp et al., 2011; Navarro, 2009) suggest that this holds

true for economic behavior as well. Some researchers have

identified a significant degree of genetic influence on variables

such as change in decisions to invest in equity securities (Barnea

et al. 2010), income (Taubman 1976), risk preferences (Zhong,

Chew et al., 2009), cooperativeness in trust games (Cesarini et al.,

2008), bargaining behavior (Wallace et al., 2007), and

preferences for giving and taking risks (Cesarini et al., 2009).

Studies in healthy people and diagnosed people with mood

disorders or psychiatric disorders have shown that: risk-taking or

risk-avoiding behavior is associated with genetic variations in

dopaminergic and serotonergic pathways. In addition, the

relationship between cognitive and emotional biases and genetic

variations in financial decisions has been discussed and proved in

other studies. Genes such as COMT, SLC6A4, BDNF and

Dopamine Receptor Genes are frequently used in such studies.

Investigation of the fundamentals of financial decisions using

molecular genetic methods has been studied not only with

dopamine receptor genes but also with many different genes and

polymorphisms. One of the genes discussed in such studies is the

MAOA gene.

1. Dopamine, Serotonin and Some Genes

Dopamine and serotonin are necessary for normal nervous system

function, and changes in the levels of these neurotransmitters

contribute to some psychological disorders. Both dopamine and

serotonin interact with other neuromodulators to influence choice

(Doya, 2008).

Dopamine and serotonin, which are chemical messengers that

transmit signals between nerve cells (neurotransmitters), are

frequently used in such studies, and U.S. National Library of

Medicine has identified 27 gene that associated with dopamine

(CHRNA4, COMT, DBH, DDC, DPYS, DRD2, DRD3, DRD4,

DRD5, EPB41L1, GBA, GCH1, GNAL, HTR1B, MAOA,

OPRM1, PARK7, PRKN, RGS9, SLC18A2, SLC6A3, SNCA,

SPR, TAAR1, TH, TOR1A, UPB1) and 14 gene that associated

with serotonin CC2D1A, DDC, FEV, GCH1, HTR1A, HTR1B,

HTR2A, MAOA, SLC18A2, SLC6A4, SNORD115-1, SPR,

TAAR1, TPH2). Given that these genes are involved in both the

dopaminergic serotonergic pathways, two pathways that play

critical roles in emotional processing, this gene may contribute to

a series of processes involved in affective processing (Gao, Liu et

al. 2017). The genes that appear to be associated with both

serotonin and dopamine are: DDC gene, GCH1 gene, HTR1B

gene, MAOA gene, SLC18A2 gene, SPR gene and TARR1 gene.

As seen as, the MAOA gene is one of the genes associated with

both dopamine and serotonin.

Johnston (1968) defined two subtypes of MAO based on the

observation that one form (A) but not the other (B) was sensitive

to the irreversible inhibitor, clorgyline. The U.S. National Library

of Medicine describes the MAOA gene and its role in the

breakdown of neurotransmitters such as serotonin and dopamine:

“The MAOA gene provides instructions for making an enzyme

called monoamine oxidase A. Specifically, monoamine oxidase

A is involved in the breakdown of the neurotransmitters

serotonin, epinephrine, norepinephrine, and dopamine. Signals

transmitted by serotonin regulate mood, emotion, sleep, and

appetite. Epinephrine and norepinephrine control the body's

response to stress. Dopamine transmits signals within the brain to

produce smooth physical movements.”

Monoamine oxidase A (MAOA) gene located in Xp11.3 spanning

15 exons containing 527 amino acids and codes for MAOA

protein. The function of MAOA enzyme is to degrade

monoaminergic neurotransmitters (adrenaline, noradrenaline,

serotonin and dopamine) in the brain. These neurotransmitters

play an important role in arousal, emotions, mood and even

affecting impulse control (Ramakrishnan and Akram Husain,

2017). There are also studies linking the MAOA gene with some

psychological disorders like schizophrenia, bipolar disorder and

major depressive disorder. Different variants of it regulate

transcription, metabolism, and signal transfer between neurons,

all of which have an effect on social interactions (Craig, 2007;

Spitzer et al., 2007). The less transcriptionally efficient alleles are

called MAOA-L, and the more efficient are called MAOA-H

(Sabol et al., 1998). MAOA-L has been found to be associated

with various kinds of antisocial behavior, including violence and

aggression, both in the field (Caspi et al., 2002) and in the lab

(Gallardo-Pujol et al., forthcoming). McDermott et al. (2009)

show an association between MAOA-L in males and behavioral

aggression following provocation.

Studies revealing the association of variations in the MAOA gene

with psychological disorders such as aggression and mood

disorder have led to the investigation of the relationship between

excessive risk-taking behavior and excessive self-esteem bias

with the MAOA gene in financial decisions. Previous literature

suggests may be individual variability in genetic alleles (Raine,

2008), and this variability can cause some irrational financial

decisions, such that individuals with a low activity form of the

gene that encodes monoamine oxidase A (MAOA-L) will be

more likely to react with aggression to challenge, and these

aggressive behaviors can cause people to behave in extreme risk.

The MAOA gene, which is thought to have a close relationship

with aggression behavior in studies about neurobiological basis

of taking economic risk, is generally considered together with

gambling addiction in studies where risk taking behavior is

examined in financial decisions.

Ibanez et al. (2000) studied 68 pathological gambling addicts and

68 control groups and investigated whether there is a relationship

between MAOA and MAOB genes and pathological gambling

disease. According to results, there were no significant

differences between pathological gamblers and healthy

volunteers in overall allele distribution at the MAOA gene

polymorphism, but there was a significant association between

allele distribution and the subgroup of severe male gamblers

compared to the males in the group of healthy volunteers.

Pérez de Castro et al. (2002) studied the relationship between

pathological gambling dependence and MAOA (MAOA-uVNTR

polymorphism) in the serotonergic system. At the end of the

study, the relationship between pathological gambling addiction

and serotonergic system was emphasized. In the experiment, the

allelic frequency of the 3-copy allele in MAOA-uVNTR

polymorphism was found to be higher in the experimental group

which was gambling dependent and lower in the control group.

Zhong, Israel et al. (2009) examined the effect of the MAOA gene

on gambling and insurance behaviors. The fact that people exhibit

high risk taking behaviors while playing games of chance, but

insuring other areas of their lives cannot be explained rationality.

They found that subjects with the high activity (4-repeat) allele

are characterized by a preference for the longshot lottery and also

less insurance purchasing than subjects with the low activity (3-

repeat) allele.

Frydman, Camerer et al. (2011) combine neuroeconomics and

behavioral genetic methods to investigate the effect of

monoamine oxidase-A (MAOA) on risk attitudes. As a result of

the study, in accordance with the previous literature, they

concluded that the carriers of MAOA-L polymorphism are more

likely to take financial risks and can make better financial

decisions at risk.

When looking at the triad of financial decision making,

personality and genetics, it should be noted that they are all

closely related. In addition, recent studies have added another

variable to this trio: Neurology. There are many studies linking

MAOA uVNTR with brain functions that is realized during

cognitive, emotional arousal and personality tests (Fan, Fossella

vd, 2003; Meyer-Linderberg, Buckholtz vd., 2006; Buckholtz,

Callicott vd. 2008; Cloninger, 1986). Additionally, some brain

imaging studies have shown an activation of similar brain areas

in aggression and cooperation (Nelson & Trainor, 2007; Decety

et al., 2004). Moreover, brain functions during cognition,

emotional arousal, personality test-takings, and working memory

activation as well as the function and anatomy of specific brain

regions in the limbic system were affected by the MAOA VNTR

(Mertins, Schote and Meyer, 2013).

Another common gene identified for dopamine and serotonin is

the DDC gene. The DDC gene provides instructions for making

the aromatic l-amino acid decarboxylase (AADC) enzyme, which

is important in the brain and nervous system, and this enzyme

takes part in the pathway that produces dopamine and serotonin.

Based on the results of studies showing that the DDC gene is

associated with some psychological disorders, such as anxiety

(Costas et al., 2010) and bipolar disorder (Børglum et al., 2003),

it can be said that genetic variations in the DDC gene can be a

candidate gene for decision making genetic studies.

Gao, Liu et al. (2017) demonstrated that the genetic variations of

the DDC gene, gene contributed to individual differences in the

susceptibility to framing. The framing effect in behavioral finance

refers the tendency to be risk-averse when options are presented

positively but be risk-seeking when the same options are

presented negatively during decision-making.

The GCH1 gene provides instructions for making an enzyme

called GTP cyclohydrolase 1. This enzyme is involved in the

production of a molecule called tetrahydrobiopterin (BH4).

Tetrahydrobiopterin is involved in reactions that produce

chemicals called dopamine and serotonin neurotransmitters,

which transmit signals between nerve cells in the brain.

The GCH1 gene is generally known as a gene with pain

sensitivity and potential to develop chronic pain (George, Wu et

al.). However, mutations in the GCH1 gene have been identified

in the following 3 clinically different neurometabolic disorders:

dystonia, hyperphenylalaninemia and compound heterozygote

mutations of the GCH1 gene with a neurologic disorder

intermediate in severity between the above disorders (Hahn, Trant

and Brownstein, 2001). However, in the literature, there is no

study showing the direct relationship of this gene to decision

making or financial decision making.

The HTR1B encoded by this intronless gene is a G-protein

coupled receptor for serotonin (5-hydroxytryptamine).

Benko et al. (2010) examined the association between the C (-

1019) G functional polymorphism, regulating the HTR1A gene

expression, and impulsiveness. The C (-1019) G genotype groups,

showed significant differences: GG type subjects showed

significantly higher motor and cognitive impulsiveness.

According to these findings suggest that the receptor gene,

HTR1A, expression was involved in a continuum phenotype of

impulsiveness. However, in the literature, there is no study

examining the relationship between HTR1B and decision-making

or financial decisions.

According to the U.S. National Library of Medicine, SLC18A2

gene encodes a transmembrane protein that functions as an ATP-

dependent transporter of monoamines, such as dopamine,

norepinephrine, serotonin, and histamine. Polymorphisms in this

gene may be associated with schizophrenia, bipolar disorder,

Parkinsonism, and other neurological/psychiatric ailments.

However, there is no evidence that the SLC18A2 gene directly

affects financial behaviors or financial decisions.

According to the U.S. National Library of Medicine, the SPR

gene provides instructions for making the sepiapterin reductase

enzyme. The sepiapterin reductase enzyme converts a molecule

called 6-pyruvoyl-tetrahydropterin to tetrahydrobiopterin.

Tetrahydrobiopterin helps process several building blocks of

proteins (amino acids), and is involved in the production of

chemicals called neurotransmitters, which transmit signals

between nerve cells in the brain. Specifically, tetrahydrobiopterin

is involved in the production of two neurotransmitters called

dopamine and serotonin. Although it was associated with

dopamine and serotonin, no direct correlation was found between

the SPR gene and decision-making or financial behavior. Like the

SPR gene, the TARR1 gene has been identified by the U.S.

National Library of Medical. According to this, the protein

encoded by this gene is a G-protein coupled receptor activated by

trace amines. The encoded protein responds little or not at all to

dopamine, serotonin, epinephrine, or histamine, but responds well

to beta-phenylethylamine, p-tyramine, octopamine, and

tryptamine. While primarily functioning in neurologic systems,

there is evidence that this gene is involved in blood cell and

immunologic functions as well. There is no evidence that the

TARR1 gene affects behaviors or financial decisions.

Discussion

When the genes associated with dopamine and serotonin are

examined, it is seen that some of the genes have proven to be

related to decision making. In particular, the findings suggest that

the MAOA gene plays a role in financial behavior and financial

decision making. Studies examining the effect of the MAOA gene

on risk-taking behavior in financial decisions are often addressed

in conjunction with gambling addiction.

In addition to genes commonly used in the field of

genoeconomics, such as COMT, BDNF, SLC6A4, studies on the

effect of variations in the MAOA gene on the financial decision

process are important for genoeconomics and neuroeconomics.

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