The influence of the HPA axis in development of psychosis

Running head: HPA AXIS AND PSYCHOSIS DEVELOPMENT 1
The Influence of the Hypothalamic-Pituitary-Adrenal (HPA) Axis on the Development of
Psychosis
Ashley L. Brodell
Cornell College

HPA AXIS AND PSYCHOSIS DEVELOPMENT 2
Abstract
Psychosis is considered one of the most devastating mental illnesses because of severe positive
symptoms that invade an individual’s life. There are a range of neurochemical and structural
abnormalities implicated in the brains of psychosis sufferers. Furthermore, the diathesis stress
model proposes that a genetic predisposition and stressful experiences within the environment
are often implicated in psychosis progression. This paper aims to review the influence of the
most universal indicators of psychosis progression, with increased hypothalamic-pituitary-
adrenal (HPA) axis activation as the central focus. Long-term HPA axis activation has a variety
of negative consequences throughout the brain, leading to psychosis in a variety of high-risk
individuals.
Keywords: psychosis, HPA axis, diathesis stress model, cortisol, dopamine

The Influence of the Hypothalamic-Pituitary-Adrenal (HPA) Axis on the Development of
Psychosis
Psychosis is a rare neurological illness that devastates the lives of its sufferers. Psychosis
sufferers experience a high reliance on antipsychotic medications throughout their lives, and
there is a high chance of relapse despite medication use (Trotman et al., 2013). Psychosocial
implications for sufferers include negative impacts on social relationships, educational
obtainment, and career (Trotman et al., 2013). Therefore, psychosis dramatically interferes with
how a sufferer lives his/her life. Psychosis onset is often associated with chronic stress, which
leads to long-term hypothalamic-pituitary-adrenal (HPA) axis dysregulation (Murri et al., 2012).
Psychotic disorders include a range of illnesses, such as schizophrenia, schizotypal disorder,
schizophreniform disorder, schizoaffective disorder, mood disorders with psychotic features,
manic bipolar episodes, and some episodes of manic depression (DSM-5: American Psychiatric
Association, 2013; Buschlen et al., 2011; Mondelli et al., 2010; Murri et al., 2012; Trotman et
al., 2013). The prevalence of psychosis varies by disorder, and the prevalence per disorder is
low. For example, it is estimated that for schizophrenia and schizophreniform disorder, the
prevalence per disorder is approximately .3%-.7% of the general population (DSM-5: American
Psychiatric Association). However, when considering the full range of psychotic illnesses, the
prevalence of psychosis in the general population is estimated at approximately 3.58% (Perälä et
al., 2007).
Although there is a low prevalence of psychotic disorders, these disorders are considered
the most serious and devastating of all mental illnesses because of the severity of symptoms
experienced (Holzman et al., 2013; Trotman et al., 2013). These symptoms include both positive
symptoms (Arseneault, Cannon, Fisher, Polanczyk, Moffitt, & Caspi 2011; Collip, Nicolson,

Lardinois, Lataster, van Os, & Myin-Germeys, 2011; Dominguez, Wichers, Lieb, Wittchen, &
van Os, 2009; Holzman et al., 2011; Lincoln, Kother, Hartmann, Kempkensteffen, & Moritz,
2011) and negative symptoms (Dominguez et al., 2009; Trotman et al., 2013). Positive
symptoms include delusions, hallucinations, disorganized thinking, catatonia, and other
disordered movements (DSM-5: American Psychiatric Association, 2013). Negative symptoms
include social withdrawal, anhedonia, blunted affect, avolition, and alogia (DSM-5: American
Psychiatric Association, 2013). Since negative symptoms are primarily characteristic of
schizophrenia and not always related to other psychotic disorders (DSM-5: American Psychiatric
Association, 2013), this review focuses on the abnormalities in the brain associated with positive
psychotic symptoms.
The purpose of this paper is to examine how HPA axis dysregulation changes the brain
both chemically and structurally (McEwen, 2008) in psychosis. Increased activation of the HPA
axis will be investigated as the central focus of psychosis development. Psychosis will then be
examined through the diathesis stress model, which suggests that psychosis develops from a
genetic disposition that is activated by environmental stressors (Pruessner, Bechard-Evans,
Boekestyn, Iyer, Pruessner, & Malla, 2013a; Trotman et al., 2013). Various abnormalities
throughout the brain will be acknowledged as a by-product of increased HPA axis activation.
Epigenetics will then be discussed in terms of the diathesis stress model, leading to the negative
impact of childhood adversity, which can cause the long-term dysregulation of the HPA axis
implicated in psychosis.
The HPA Axis in Relation to Psychosis
Previous research suggests that indices of HPA activity, such as cortisol and
adrenocorticotropic hormone (ACTH), are elevated in psychosis patients, especially when

patients are non-medicated and experiencing his/her first psychotic episode (Walker, Brennan,
Esterberg, Brasfield, Pearce, & Compton, 2010; Walker et al., 2013). Typical activation of the
HPA axis begins with stress exposure, which activates the paraventricular nucleus of the
hypothalamus and releases corticotrophin releasing hormone (CRH) from the axon terminals into
the pituitary gland (Holzman et al., 2013). CRH stimulates release of ACTH from the anterior
pituitary gland into the bloodstream (Walker et al., 2013; Walter et al., 2015). Once ACTH has
traveled through the bloodstream to the adrenal gland, ACTH stimulates the adrenal gland and
produces cortisol (Holzman et al., 2013; Walter et al., 2015). Cortisol acts on tissues while it
travels throughout the body and finally crosses the blood brain barrier. Once the blood brain
barrier is crossed, cortisol acts on various regions within the brain that have a high concentration
of glucocorticoid receptors (Hotltzman et al., 2013).
Glucocorticoid receptors are densely packed within the mesolimbic system, which
contains regions such as the hippocampus, and has shown to be dysfunctional in patients with
psychosis (Holzman et al., 2013; Trotman et al., 2013; Walker et al., 2013). Furthermore,
glucocorticoid receptors are thought to be downregulated in the mesolimbic system of psychotic
patients, which suggests reduced negative feedback. This means that the mechanisms that usually
signal the adrenal gland to stop producing cortisol are not active (Walker, Brennan, Esterberg,
Brasfield, Pearce, & Compton, 2010; Walker et al., 2013). Thus, the HPA axis serves as a
mediator between stressful experiences and positive symptoms of psychosis, with high cortisol
levels as a risk factor for psychosis onset (Collip et al., 2011; Holzman et al., 2013; Pruessner et
al., 2008).
The HPA axis also works as a mediator between genetic vulnerability, stressful
experiences, and mental illness onset (Lataster, Collip, Lardinois, van Os, & Myin-Germeys,

2010; Lincoln et al., 2015; Pruessner et al., 2013a). The diathesis stress model suggests that a
genetic predisposition for psychosis increases vulnerability to environmental stressors, and stress
from the environment activates this genetic predisposition (Lataster et al., 2010). However,
genetic vulnerability and significant environmental stress does not guarantee the development of
psychosis (Pruessner et al., 2013a). Overall, psychosis sufferers tend to have more environmental
traumas and higher genetic risk, which leads psychosis sufferers to be more reactive to stressful
situations, reflected by heightened HPA axis activity (Lataster et al., 2010).
Furthermore, research has suggested that individuals who develop psychosis have higher
than average cortisol levels up to one year before their first psychotic episode, which is
associated with an increase in subclinical positive symptoms (Walker et al., 2013). Cortisol
levels are also found to be higher immediately before psychotic episodes in individuals who have
an established psychotic disorder (Walker et al., 2010). This may be due to increased threat
perceptions that cause paranoia and an increased stress response (Walker et al., 2013).
Throughout the course of psychosis, the HPA axis goes through various changes, with a decline
in cortisol being associated with a decline in positive psychotic symptoms (Murri et al., 2012;
Walker et al., 2013). This decline in symptoms is correlated with the use of antipsychotic
medication, which has been shown to reduce cortisol levels (Murri et al., 2012).
Discrepant Cortisol Findings
Although previous findings have suggested that HPA axis activity and cortisol levels are
high in individuals with psychosis when compared to healthy controls (Collip et al., 2011;
Holzman et al., 2013; Pruessner et al., 2008), discrepant findings have reported low cortisol
levels in individuals with chronic psychosis (Holzman et al., 2013; Lincoln et al., 2015). Lincoln
and colleagues (2015) used two experimental conditions involving noise and psychosocial stress

to cause a stress response in their participants. Results suggested that cortisol release was
significantly decreased in chronic psychosis participants when compared to controls in both of
the stressful conditions. However, psychosis patients self-reported significantly more stress in all
conditions, suggesting higher stress reactivity, which was not reflected by higher cortisol levels
as predicted (Lincoln et al., 2015). Lincoln and colleagues (2015) suggested that these results
indicate hypocortisolemia in patients with chronic psychosis. Hypocortisolemia may serve as a
protective physical response to long lasting hyperarousal due to increased HPA axis activation
and cortisol release throughout the course of chronic psychosis (Holzman et al., 2013).
However, there are alternative explanations about this discrepancy. The first explanation
is that the stressors experienced in a controlled experimental setting may not be as stressful to
participants with psychosis. The severe stress caused by positive symptoms during chronic
psychosis may heighten HPA axis activity beyond environmental stressors; therefore, increased
cortisol would not be reflected by experimental conditions (Holzman et al., 2013; Lincoln et al.,
2015; Pruessner et al., 2013a; Reniers et al., 2013). Furthermore, the participants may have been
asymptomatic during the time of the experiment, since a decline in cortisol is associated with a
decline in psychotic symptoms (Murri et al., 2012; Walker et al., 2013). Finally, psychosis
sufferers who participated in studies where lower than average cortisol levels were found were
taking antipsychotic medication, which has been shown to decrease both cortisol and dopamine
levels (Lincoln et al., 2015; Reniers et al., 2013).
Cortisol and Dopamine
Additionally, research suggests that as cortisol levels and positive symptoms increase,
dopamine levels also increase (Collip et al., 2011; Dominguez et al., 2009; Holzman et al., 2013;
Walker et al., 2013). Researchers have hypothesized that hyperactivity of dopaminergic

pathways within the mesolimbic system leads to the sensitization of dopamine receptors
(Dominguez et al., 2009). Increased sensitization to dopamine contributes to illness progression,
increasing the experience of positive symptoms (Dominguez et al., 2009; Holzman et al., 2013).
Environmental stressors contribute to dopaminergic sensitization through continuous cortisol
release from the HPA axis, leading to an increase in dopaminergic transmission (Dominguez et
al., 2009; Murri et al., 2012; Pruessner et al., 2008; Pruessner et al., 2013a; Trotman et al., 2013),
which contributes to the emergence of psychotic symptoms (Walter et al., 2015). Thus, high
dopamine levels are associated with both clinical and subclinical positive symptoms and the
more dopamine in the brain, the more likely high-risk individuals are to transition to psychosis
(Dominguez et al., 2009).
Once an individual transitions to psychosis, he/she is often prescribed antipsychotic
medication, which has been shown to decrease positive symptoms by working as D2 receptor
antagonists (Holzman et al., 2013). The use of antipsychotic medication is associated with both a
decline in cortisol and dopamine levels within the mesolimbic system (Holzman et al., 2013;
Lincoln et al., 2015; Pruessner et al., 2008; Pruessner et al., 2013a; Pruessner, Vracotas, Joober,
Pruessner, & Malla, 2013b; Reniers et al., 2013; Trotman et al., 2013; Walker et al., 2010;
Walker et al., 2013). The association between cortisol and dopamine was also exhibited through
an animal study that examined an unnamed agent that worked as a glucocorticoid receptor
suppressor, which decreased the binding of cortisol throughout the mesolimbic system (Holzman
et al., 2013). This agent decreased both dopamine levels and positive symptoms (Holzman et al.,
2013). In an additional animal research study, it was shown that agents that increased dopamine
activity also increased HPA activity and cortisol secretion (Holzman et al., 2013), thus alluding
to a strong association between cortisol and dopamine in psychosis. Research conducted using

substances that altered both dopamine and glucocorticoid receptor activity suggests that there is a
positive correlation between cortisol and dopamine in the etiology of psychosis (Holzman et al.,
2013), but causation continues to be unclear.
Prevalent Structural Changes
Hippocampal Volume Reduction
Moreover, high dopamine and cortisol levels both exhibit damaging effects on the
hippocampus, which is a region within the mesolimbic system (Pruessner, Lepage, Collins,
Pruessner, Joober, & Malla, 2015). Research suggests that left hippocampal volume is reduced in
both subclinical and clinical psychosis due to increased cortisol production by the HPA axis
(Buehlmann et al., 2010; Mondelli et al., 2014; Mondelli et al., 2010; Reiners et al., 2014;
Pruessner et al., 2015; Walker et al., 2013; Wood et al., 2005; Wood et al., 2010). This decrease
in hippocampal volume is likely caused by densely packed glucocorticoid receptors within this
region, leading the hippocampus to be sensitive to heightened HPA axis activation and cortisol
secretion (Collip et al., 2011; Mondelli et al., 2010). Besides increased HPA axis activity,
decreased left hippocampal volume is also associated with an increase in dopamine, positive
symptoms and cognitive decline (Pruessner et al., 2015). However, small left hippocampal
volume is not unique to psychosis; other mental disorders that are associated with increased HPA
axis activation include depression, anxiety, and post-traumatic stress disorder (PTSD) (Wood et
al., 2005). Therefore, small left hippocampal volume alone is not a reliable indicator of
psychosis.
Discrepant findings for hippocampal volume. Considering that psychosis is a long
term neurological illness, there can be variations in hippocampal volume depending on how
much the illness has progressed (Buehlmann et. al., 2010; Reniers et al., 2013). Psychosis studies

typically use participants who are at different stages in the illness, such as ultra-high risk
participants, first episode psychosis patients, and chronic psychosis patients (Buehlmann et al.,
2010; Collip et al., 2011; Wood et al., 2010). When ultra-high risk participants are used in
research, there is no guarantee that these participants will transition to psychosis at a later time
period (Reniers et al., 2013). Since few ultra-high risk participants’ transition to psychosis and
transition rates vary per study, results must be interpreted carefully to avoid the assumption that
ultra-high risk participants will develop their first psychotic episode.
A MRI study conducted by Buehlmann and colleagues (2010) included an ultra-high risk
group, a first episode group, and a control group when comparing hippocampal volume. The
results showed that the hippocampal volume of first episode patients was lower by 6.9% when
compared to an ultra-high risk participant group. When compared to the control group, it was
found that first episode psychosis patients had hippocampal volume that was lower by 4.5%
(Buehlmann et al., 2010). These results suggest that the ultra-high risk participant group had the
largest hippocampal volume on average when compared to the averages of both controls and first
episode psychosis patients (Buehlmann et al., 2010). This is counter to expectations since the
subclinical stage of psychosis is associated with increased HPA axis reactivity, and thus, would
hypothetically lead to decreased hippocampal volume due to heightened cortisol release.
Hippocampal shrinking may not have been detected in the ultra-high risk group because
of the potential for higher hippocampal volume associated with an increase in inflammation of
the hippocampus (Reniers et al., 2013). This increase in inflammation could be associated with
an increase in pro-inflammatory cytokines, which trigger immunological reactions in times of
high stress (McEwen, 2008; Mondelli, 2014). The hippocampus is especially vulnerable to
immunological processes because of the densely packed glucocorticoid receptors (Mondelli et

al., 2014), leading to inflammation within the region as neurons undergo apoptotic processes
(Buehlmann et. al., 2010; Reniers et al., 2013). Therefore, during the subclinical stage of
psychosis, hippocampal volume may become larger in response to adverse reactions to stress
hormones.
Lack of Neuroprotection
Furthermore, protein called BDNF shows protective effects on hippocampal volume
when present at normal levels in the brain (Mondelli et al., 2014). These protective effects
include proliferation, regeneration, and survival of neurons within the hippocampus (Mondelli et
al., 2014; Walker et al., 2013). Even if high levels of cortisol are bound to glucocorticoid
receptors in the hippocampus, past research suggests that neurogenesis still occurs if an
individual is in an enriched environment because BDNF is maintained at normal levels
(McEwen, 2008; Mondelli et al., 2014). However, if an enriched environment is not available,
prolonged stress, heightened HPA axis activation, and high cortisol release have been shown to
reduce BDNF levels within the brain (Trotman et al., 2013). Low BDNF is associated with
decreased dendritic branching and neurogenesis within the hippocampus, which decreases
hippocampal volume (Mondelli et al., 2010; Mondelli et al., 2014; Pruessner et al., 2015).
This association was exemplified in a study conducted by Mondelli and colleagues
(2014). Results suggested that psychosis participants had lower BDNF expression, higher levels
of pro-inflammatory cytokines, and higher cortisol when compared to healthy controls (Mondelli
et al., 2014). All of these variables were shown to be strong predictors of hippocampal volume in
a multiple regression model, with 70% of the variability in hippocampal volume explained by
these variables (Mondelli et al., 2014). Thus, an increase in HPA axis activation may have a
causal role in the suppression of BDNF production.

Pituitary Enlargement
Psychosis research has also shown that an increase in HPA axis activation is associated
with an increase in pituitary gland volume, and this increase is associated with the production of
ACTH (Bushchlen et al., 2011; Holzman et al., 2013; Walter et al., 2014). On average, pituitary
volume is 12% higher in psychosis suffers when compared to controls (Walter et al., 2014). A
larger pituitary gland is thought to be a structural reflection of overall HPA axis activity because
volume increases as the number and/or size of corticotrophin-releasing cells becomes higher.
Furthermore, if a sufferer has higher pituitary volume at psychosis onset, it is often associated
with less symptom improvement over time (Buschlen et al., 2011; Mondelli et al., 2014; Walker
et al., 2013). Finally, pituitary volume was shown to decrease with atypical antipsychotic
treatment, which suggests that this medication improves HPA axis regulation (Buschlen et al.,
2011).
Gender Differences in Psychosis
Furthermore, research has demonstrated that the HPA axis tends to be more dysregulated
in male psychosis patients when compared to female psychosis patients. When males are
diagnosed with psychosis, there tends to be a higher rate of treated instances, earlier onset,
poorer premorbid adjustment, longer hospital stays, more negative symptoms, poorer response to
treatment, and poorer long term outcomes (Pruessner et al., 2008). Cortisol follows a circadian
rhythm cycle, in which cortisol levels are highest during the first hour of awakening and become
lower throughout the day (Collip et al., 2011; Pruessner et al., 2008; Pruessner et al., 2013b).
Pruessner and colleagues (2008) measured cortisol awakening response (CAR) by having
participants take cortisol samples immediately after awakening, 30 minutes after awakening, and
60 minutes after awakening. Generally, low cortisol levels upon awakening reflected HPA axis

dysregulation through a blunted CAR (Pruessner et al., 2008; Pruessner et al., 2013b). Research
such as this has shown a blunted CAR in male, but not female, participants (Pruessner et al.,
2008; Pruessner et al., 2013b; Pruessner et al., 2015). Blunted CAR in males may be associated
with poorer outcomes in psychosis because a dysregulated HPA axis response may limit a
sufferer’s ability to adapt to stress (Pruessner et al., 2008; Pruessner et al., 2015).
The estrogen hypothesis suggests that females may be more resilient to both stress and
psychosis because estrogen receptors are densely packed throughout the HPA axis, mesolimbic
pathways, and hippocampus (Pruessner et al., 2015). Females have a lower prevalence rate of
psychosis before menopause; higher rates of onset afterward and the severity of psychotic
symptoms are variable, depending on stage in menstrual cycle (McEwen, 2008; Trotman et al.,
2013). These examples demonstrate that a female’s risk of psychosis onset goes down during
times of high estrogen levels. This resistance is further exemplified by animal studies, which
have shown evidence of the regulatory effects estrogen has on glucocorticoid receptors, thus
decreasing cortisol binding (Trotman et al., 2013). Past research has also suggested that estrogen
may serve a neuroprotective function by regulating dopamine levels (Trotman et al, 2013),
although the exact mechanism of estrogen’s neuroprotective effect is unknown. Finally,
hippocampal volume is shown to be higher in females with psychosis then males with psychosis,
reflected by increased cognitive capabilities in psychotic females (Pruessner et al., 2015).
Psychosis Development
Psychosis tends to develop throughout one’s life, with onset occurring in the early
twenties (Trotman et al., 2013). Although the diathesis stress model indicates that an increase in
environmental stressors mediates psychosis development, past research suggests that individuals
with psychosis do not necessarily experience more stressful life events than controls, but these

events are interpreted as more stressful in those that go on to develop psychotic disorders
(Mondelli et al., 2014; Pruessner et al., 2011; Wood et al., 2005). High stress reactivity is seen in
individuals with both high genetic risk (first degree relative with psychosis) and high
psychometric risk (measured by the psychosis liability scale) (Lataster et al., 2010; Pruessner et
al., 2013a; Reniers et al., 2013; Wood et al., 2005). The perception of events as highly stressful
and an increased stress response seem to have the greatest influence on psychosis development,
which reflects both genetic and environmental influences (Collip et al., 2011; Holzman et al.,
2013; Lincoln et al., 2015; Pruessner et al., 2011). High stress reactivity to acute and chronic
stressors implicates HPA axis dysregulation during the development of psychotic disorders,
which may have a genetic basis (Pruessner et al., 2011).
Studies on functional polymorphism genes show an association with a mutation that
reflects increased emotional stress reactivity (Lataster et al., 2010). One example of a functional
polymorphism gene is called the Vall58Met functional polymorphism of the catechol-O-
methyltransferase, and this specific gene has been implicated in studies with patients diagnosed
with psychotic disorders (Lataster et al., 2010; Rutten & Mill, 2009). This association suggests
possible epigenetic influences. Epigenetics are heritable and reversible changes in methylation of
genes, but these changes do not cause alterations of the underlying DNA sequence (Lataster et
al., 2010; Rutten & Mill, 2009). Animal studies have further shown that through early maternal
behavior, such as not licking offspring after feeding, DNA methylation can be altered in neuronal
receptors for genes implicated in offspring stress sensitivity (Lataster et al., 2010). This can
cause lasting alterations in stress response as the offspring becomes older (Lataster et al., 2010;
Walker et al., 2013). Epigenetic alterations such as these reduce the transcription of affected
genes, and thus are not reproduced through mitosis. Since the relationship between epigenetics

and psychosis development is in the early stages of research, the exact magnitude of how
epigenetics influence psychosis development remains unclear and only a few genes have been
identified.
Childhood Adversities and Trauma
Childhood is a developmentally important stage in one’s life, which is represented by the
negative impacts of environmental stressors, which can activate genetic vulnerability and
influence the development of the HPA axis (Thompson et al., 2009). Since childhood is an
important time for HPA axis development, parents have a strong influence on the child’s
environment, which affects the quantity and quality of stress a child experiences (Pruessner et
al., 2013b; Thompson et al., 2009). If a child experiences a lot of negative events, the risk of
developing psychosis increases, especially if the child has learned maladaptive coping patterns in
response to stress and has a genetic predisposition (Verease et al., 2012). A study examining
participants in a critically high risk sample found a 70% prevalence of childhood trauma in those
who developed psychosis (Holzman et al., 2013). This high prevalence of childhood trauma in
psychosis may be due to early dysregulation of the HPA axis in response to adverse experiences.
The type of childhood trauma also has an influence on the development of psychosis. For
example, if a genetically high-risk child experiences situations where there was an intention to
harm the child, especially parental figures and peers, the child is approximately three times more
likely to develop psychosis in adulthood (Arseneault et al., 2011). If a child experiences more
than one trauma in childhood, the genetically at risk child is five times more likely to develop
psychosis (Arseneault et al., 2011). Research also suggests that if someone experienced one type
of adverse event or trauma in childhood, there was a greater likelihood of experiencing another
(Arseneault et al., 2011; Varese et al., 2012). Childhood trauma is associated with the severity of

positive symptoms. Severe and persistent trauma can cause changes in HPA axis reactivity and
dopamine augmentation (Holzman et al., 2013; Thompson et al., 2013). HPA axis dysregulation
in early life due to trauma may enhance threat perceptions and the stress response, which
contributes to the manifestations of subclinical positive symptoms in childhood, such as paranoia
(Arseneault et al., 2011; Holzman et al., 2013; Thompson et al., 2009). Overall, greater exposure
to trauma in childhood predicts earlier onset of psychosis in populations at high genetic risk
(Holzman et al., 2013).
Limitations and Future Directions
The most prevalent limitation in psychosis research is that the participant groups used in
these studies are at various stages before and after psychosis diagnosis. Some participants that
are used are at an ultra-high genetic risk for psychosis, as determined by a close relative who has
psychosis. Other participants may be exhibiting subclinical positive symptoms but do not meet
full diagnostic criteria of a psychotic disorder. An issue with these participant groups is that both
ultra-high risk and subclinical participants do not always transition to psychosis, with a transition
rate of 20% - 40% (Walker et al., 2010; Walker et al., 2013), depending on the study. Therefore,
chemical and structural brain abnormalities in a subclinical or ultra-high risk group may not be
representative of the psychosis population. First episode psychosis patients and chronic
psychosis patients also participate in these studies. However, most of these participants are
taking antipsychotic medication, which can change neural structures while remitting positive
symptoms. Measurements of cortisol and MRI brain scans may not represent abnormalities of a
natural psychosis disorder in participants who are taking antipsychotic medication (Thompson et
al., 2009). Since first episode psychosis patients have been on antipsychotic medication for a
short amount of time, it may be beneficial to recruit this group for future psychosis studies.

Overall, there is a need of more longitudinal studies that track participants from subclinical
psychosis to clinical psychosis to gain a better understanding of how psychosis develops
(Buehlmann et al., 2010; Thompson et al., 2009; Pruessner et al., 2013a).
In order to better understand the development of psychosis, there needs to be a greater
research focus on neurotransmission, neurohormonal signaling, pathophysiological changes,
epigenetic processes, and gene-environment interactions (Walker et al., 2013; Wood et al.,
2005). Research such as this will provide a more comprehensive understanding of psychosis,
which can lead to better treatments in a clinical environment. Although HPA axis dysregulation
shows an obvious connection with high-risk individuals, first episode psychosis patients, and
chronic psychosis patients, elevations of cortisol levels is not the best predictor of psychosis
onset. It is important to further research different mechanisms that are specific to psychosis
onset, such as dopamine.
Research on dopamine thus far has primarily examined the effects of antipsychotic
medication on D2 receptors. Since antipsychotics improve positive symptoms through this
mechanism of action, theorists hypothesized that dopamine is central to the development of
positive symptoms (Collip et al., 2011; Dominguez et al., 2009; Holzman et al., 2013). However,
evidence is lacking as to how dopamine levels in the brain alone influence positive symptoms.
Future research should focus on dopamine levels in the brain to determine the magnitude of
dopamine’s involvement in the production of positive symptoms. It is possible that reducing the
level of one neurotransmitter has the ability to reduce the levels of other neurotransmitters, and
thus restore balance within the brain, which makes antipsychotics effective in treating positive
symptoms. However, with antipsychotic use there is a high chance of patient relapse (Trotman et
al., 2013), which suggests that dopamine is not the primary mechanism implicated in psychosis.

This leads to the conclusion that various neurotransmitters are implicated in psychosis
beyond dopamine. Since dopamine levels are associated with cortisol levels (Holzman et al.,
2013), other major neurotransmitter systems can be affected by this disrupted neurochemistry,
such as GABA, glutamate, and serotonin (Holzman et al., 2013; Trotman et al., 2013 Walter et
al., 2010). This implies that a change in one neurotransmitter system can affect the balance of
another, thus causing detrimental disruptions in neurochemistry (Walker et al., 2010). Although
research has implicated various neurotransmitter system changes throughout the course of
psychosis, these changes are not well understood and under researched. In order to work towards
grasping a complete understanding of psychosis, further research should examine this complex
relationship between different neurotransmitter systems.
Another system that may be implicated in the development of psychosis is referred to as
the sympathetic adrenal- medullary (SAM) system, which produces epinephrine and
norepinephrine during stressful experiences (McEwen, 2008). The SAM system is not often
emphasized during psychosis research although these chemicals affect the brain and body during
stressful experiences. Additionally, a few studies have demonstrated decreased cortisol levels
when the psychosis participants self-reported high feelings of stress (Lincoln et al., 2015;
Reniers et al., 2014). One study in particular found that despite decreased cortisol, participants
with psychosis had an elevated heart rate when compared to controls, which is an indicator of
sympathetic activity (Lincoln et al., 2015), possibly implicating epinephrine and norepinephrine
in psychosis etiology. Thus, the SAM system may be implicated in the psychosis stress response
and should be examined further.
Further research should also be conducted to better understand the complex relationship
between genes, environment, and psychosis development. Specifically, epigenetic processes

should be researched as a likely mediator between genetic predisposition and environmental
influences. Since the methylation of genes deactivates transcription and this process is able to be
reversed under the right circumstances (Rutten & Mill, 2009), genes that are associated with the
development of psychosis could be targeted through interventions. For example, Val66met
polymorphism downregulates BDNF production in the brain through methylation and has been
implicated in psychosis sufferers (Rutten & Mill, 2009). Previous research indicates that the
presence of an enriched environment in stressful situations helps maintain normal BDNF levels
(McEwen, 2008; Mondelli et al., 2014), and when BDNF levels are low in the hippocampus,
shrinking occurs. Thus, an enriched environment may prevent or reverse the methylation of
Val66met polymorphism, causing BDNF to remain at normal levels. Once epigenetics are better
understood in relation to psychosis, specific interventions such as this could be created to target
and reverse methylation processes before psychosis onset occurs.
In conclusion, psychosis is a complex neurological disease that changes the structure and
chemistry of the brain in many ways. These severe abnormalities are reflected by the detrimental
positive symptoms that have a negative impact on the lives of psychosis sufferers. Since these
abnormalities are not well-understood, research must be conducted in multiple areas to increase
the effectiveness of treatments and interventions for both psychosis patients and those at high
genetic and/or environmental risk. Although psychosis is often misunderstood, recent
developments in research suggest that much progress has been made in understanding the
neurological attributes of this disease.

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