Neuroticism from the point of Neurobiology
From the point of neurobiology, neuroticism is a personality trait that is linked to differences in the structure and function of specific brain regions. Research has shown that individuals who score high on measures of neuroticism tend to exhibit heightened activity in brain regions associated with emotional processing, such as the amygdala.
Other brain regions that have been implicated in neuroticism include the prefrontal cortex, which is involved in cognitive control and decision-making, and the anterior cingulate cortex, which is involved in emotional regulation. Differences in the structure and function of these brain regions have been observed in individuals high in neuroticism, suggesting that neuroticism may have a neurobiological basis.
In addition to its association with specific brain regions, neuroticism has also been linked to changes in the levels of certain neurotransmitters, such as serotonin and dopamine, which are involved in mood regulation. Overall, neurobiology provides important insights into the underlying mechanisms of neuroticism, and offers a promising avenue for the development of new treatments for individuals struggling with this personality trait.
The Influence of Genetics and Neurobiology on
The general biological risk factor is primarily influenced by genetics and neurobiology, which contribute to personality traits and temperament styles (Barlow, 2000). The triple vulnerability theory was developed in relation to the emergence of anxiety and emotional disorders. Extensive research in family and twin studies has established a genetic connection to emotional disorders (Hettema, Neale, & Kendler, 2001; Skre, Onstad, Torgersen, Lygren, & Kringlen, 1993). Additionally, neuroticism is also influenced by genetics, accounting for approximately 40% to 60% of the trait's variation (Bouchard & Loehlin, 2001; Clark et al., 1994; Kendler, Prescott, Myers, & Neale, 2003).
Studies examining self-report personality measures in twins have consistently found that genetics play a significant role in predicting personality, accounting for almost half of the variance. On the other hand, shared environmental factors like parental socioeconomic status and religious traditions have little to no impact, while nonshared environmental effects such as different teachers, leisure activities, and life events contribute to the remaining variance (Turkheimer, 2000).
Recent research has revealed that genetic contributions to neuroticism are more influential in younger individuals, whereas environmental factors have a greater influence in older adults (Laceulle, Ormel, Agen, Neale, & Kendler, 2013). Neuroticism tends to remain relatively stable after emerging in childhood but gradually decreases with age, a pattern observed in various studies (Eaton, Krueger, & Oltmanns, 2011; Roberts & Mroczeck, 2008; Roberts, Walton, & Viechthauer, 2006). However, there is considerable individual variability in the magnitude of this change (Helson, Jones, & Kwan, 2002; Mroczek & Spiro, 2003; Small, Hertzog, Hultsch, & Dixon, 2003).
As individuals age, the persistence of neuroticism seems to be influenced by cumulative environmental factors. This highlights the significance of interactions between genetically influenced physiological processes and the environment (Kandler et al., 2010).
The Genetic Basis of Neuroticism
The genetic factors associated with neuroticism are connected to a neurobiological inclination for increased reactivity in emotion-generating regions, particularly heightened activity in the amygdala, as well as reduced or ineffective inhibitory control by the prefrontal structures (Keightley et al., 2003; Stein, Simmons, Feinstein, & Paulus, 2007; Westlye, Bjonebekk, Grydeland, Kaufmann, & Walhovd, 2011).
Excessive amygdala responses are connected to a specific genetic variation in the promoter region of the serotonin transporter gene (SHTTPR). Individuals who have a low-expressing genotype (two short alleles) show greater amygdala responses to emotional stimuli (Drabant et al., 2012; Lonsdorf et al., 2011; Munafo, Brown, & Hariri, 2008). They also exhibit reduced functional connectivity between emotion-generating regions like the amygdala and structures involved in inhibitory control, such as the ventromedial prefrontal cortex (Pezawas et al., 2005).
This particular genetic variation, known as the s/s allele functional polymorphism, is independently associated with neuroticism (Lesch et al., 1996; Montag, Basten, Stelzel, Fiebach, & Reuter, 2010; Stein, Campbell Sills, & Gelernter, 2009). Moreover, individuals with this genetic variation are more susceptible to developing psychopathology following life stressors (Caspi et al., 2003; Owens et al., 2012).
Caution should be exercised when interpreting these findings, as researchers conducting large-scale studies on the effects of this functional polymorphism have obtained varied or non-replicated results (Terracciano et al., 2009). Nonetheless, one potential pathway to the development of neuroticism could involve a genetically mediated heightened sensitivity to unpleasant or potentially threatening stimuli, along with a reduced capacity to regulate activation once the threat subsides or threat-related circumstances change.
The Interplay of Physiological Reactivity and Neuroticism
It is crucial to acknowledge that the heightened activity of neural circuits in response to stress and fear is not solely attributed to genetic factors or biological predispositions. Stressful or traumatic experiences during critical periods of development also play a significant role (Gunnar & Quevedo, 2007; Lanius, Frewen, Vermetten, & Yehuda, 2010; Rosen & Schulkin, 1998). In other words, early adversity shapes the stress response that appears to underlie the neurotic phenotype (Francis, Champagne, Liu, & Meaney, 1999; Liu et al., 1997).
Moreover, it is important to recognize that physiological reactivity to stressors, such as heightened arousal, is not inherently indicative of neuroticism. In fact, arousal responses serve as an adaptive mechanism that allows individuals to exhibit appropriate behavioral responses in the face of stressors. Pathology arises when the arousal response system misfires, either in an inappropriate context or at an excessively intense level. Therefore, it is not solely biology that leads to maladaptive outcomes. Instead, the development of neuroticism occurs when heightened physiological reactivity combines with a psychological perception of the stressor's unpredictability or uncontrollability (Koolhaas et al., 2011).
Brain imaging studies
Brain imaging studies have used various imaging techniques, such as functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and electroencephalography (EEG), to investigate the neural correlates of neuroticism. These studies have found that individuals who score high on measures of neuroticism tend to exhibit differences in the structure and function of specific brain regions compared to those who score low on neuroticism.
For example, neuroimaging studies have shown that individuals high in neuroticism tend to exhibit increased activity in brain regions involved in emotional processing, such as the amygdala and insula. These regions are known to be involved in processing negative emotions, such as fear and anxiety.
In contrast, individuals low in neuroticism tend to exhibit greater activity in brain regions involved in cognitive control, such as the prefrontal cortex. This region is responsible for regulating emotional responses and decision-making processes.
The role of the amygdala in neuroticism
The amygdala is a brain region that plays a critical role in emotional processing, particularly in the processing of fear and anxiety. In individuals with high levels of neuroticism, studies have shown that the amygdala tends to be hyper-responsive to emotional stimuli, such as threatening faces or negative words. This hyper-responsiveness can lead to increased levels of anxiety and a tendency to experience negative emotions more frequently and intensely.
Research has also shown that the amygdala interacts with other brain regions, such as the prefrontal cortex and the hippocampus, to regulate emotional responses and memory. In individuals with high levels of neuroticism, this regulation may be disrupted, leading to an increased tendency to ruminate on negative events and experiences.
Other brain regions are also implicated
Other brain regions that have been implicated in neuroticism include the anterior cingulate cortex (ACC), the insula, and the hippocampus.
Studies using brain imaging techniques such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) have shown that individuals with high levels of neuroticism tend to have increased activation in the ACC and insula in response to emotional stimuli. The ACC is involved in cognitive control, attention, and decision-making, while the insula is involved in interoception (the sense of the internal state of the body) and emotional processing.
The hippocampus, a brain region important for memory and learning, has also been found to be associated with neuroticism. Studies have shown that individuals with high levels of neuroticism tend to have smaller hippocampal volumes, which may contribute to difficulties with emotion regulation and memory.
The relationship to other psychological disorders
Neuroticism has been found to be closely related to a number of other psychological disorders, both in terms of symptom overlap and underlying mechanisms. Some of the disorders that are commonly associated with neuroticism include:
Anxiety disorders: Neuroticism and anxiety disorders share many common symptoms, such as excessive worrying, fear, and avoidance. Individuals with high levels of neuroticism are more likely to develop anxiety disorders such as generalized anxiety disorder, social anxiety disorder, and panic disorder.
Mood disorders: Neuroticism is also associated with mood disorders such as major depressive disorder and bipolar disorder. Individuals with high levels of neuroticism may be more vulnerable to negative mood states and have difficulty regulating their emotions.
Obsessive-compulsive disorder (OCD): Neuroticism has been found to be a risk factor for developing OCD, which is characterized by intrusive, repetitive thoughts and compulsive behaviors.
Substance use disorders: Individuals with high levels of neuroticism may be more likely to use drugs or alcohol as a way of coping with their negative emotions, which can increase their risk of developing substance use disorders.
Neuroticism appears to be a broad vulnerability factor for a range of psychological disorders, suggesting that addressing neuroticism may be an important part of prevention and treatment efforts for these conditions.
Neuroticism is a distinct construct
Neuroticism is considered a distinct personality trait and a core dimension of personality that is distinct from other personality traits such as extraversion, agreeableness, conscientiousness, and openness to experience. Neuroticism is characterized by a tendency to experience negative emotions such as anxiety, fear, worry, and sadness, and to respond to stressors with emotional reactivity and heightened arousal.
Research has consistently shown that neuroticism is a stable personality trait that is relatively consistent across time and situations, and that it has a strong genetic and biological basis. Neuroticism has also been found to be associated with a range of important outcomes, such as mental and physical health, academic and occupational success, and relationship quality.