Anger is “an approach-related emotional state” with specific physiological, cognitive, and behavioral elements that “occur in response to unpleasant or undesired events” (Alia-Klein et al., 2018, p. 1). The study of anger is not yet complete; in fact, according to Garfinkel et al. (2015), it has been investigated to a lesser extent than some other emotions like fear and happiness. As a result, there are multiple topics that still require the attention of the researchers. For instance, the neurobiological mechanisms of anger are not fully explored (Alia-Klein et al., 2018; Denson, Dobson-Stone, Ronay, Hippel, & Schira, 2014; Hood & Amir, 2018). The connection between the physiological changes and brain activity that are related to anger also requires additional study (Garfinkel et al., 2015) Moreover, anger has varied manifestations in different people, and the investigation of the reasons for these variations is also a significant and understudied topic (Denson et al., 2014). All these aspects of anger will be considered in this literature review.
The reason for writing this paper is that the study of anger can have important implications. First of all, while anger is necessary for human survival (Gross, 2015), it is also often associated with antisocial, violent behavior, which is why it is a socially relevant topic (Alia-Klein et al., 2018), Secondly, anger is often characteristic of various disorders, and it has an impact on the quality of life and safety of the affected people (Alia-Klein et al., 2018; Hasler et al., 2017; Kolla, Meyer, Bagby, & Brijmohan, 2017). Thirdly, chronic anger causes problems for the people who experience them; for instance, it can cause disruptions in natural biological rhythms (Hood & Amir, 2018). Overall, anger has a significant impact on human beings, which is why its investigation is necessary and should yield the information which can be used for the interventions that can assist in anger regulation (Gross, 2015). The present literature review will offer a synthesis of the existing research with attention paid to the physiological aspect of anger response, brain areas associated with it, and individual expressions, as well as the emotional regulation, related to anger.
Physiological Response to Anger
Anger is expressed not only in the brain, but also in the body, and the physiological changes that occur during an anger response also have an impact on the cognitive processes and behaviors associated with it (Garfinkel et al., 2015). Increased heart rate and blood pressure are the primary elements of the physiological response to anger in humans (Deng, Chang, Yang, Huo, & Zhou, 2016; Gross, 2015). For instance, increased systolic blood pressure is characteristic for people with trait anger (that is, people who exhibit a predisposition to anger and experience it often) (Garfinkel et al., 2015). It is noteworthy that men tend to exhibit a higher heart rate in response to negative emotions, including anger, than women (Deng et al., 2016). Therefore, there can be some variations in the physiological changes associated with anger, but, in general, it is connected to cardiovascular arousal.
Consequently, it should be noted that chronic anger, as well as unhealthy anger regulation approaches, are associated with increased risks of cardiovascular diseases and hypertension (Gross, 2015). Additionally, anger also disrupts natural biological rhythms, resulting, for example, in poor sleep (Hood & Amir, 2018). As a result, the study of the effect of anger on the human cardiovascular system requires the attention of healthcare research (Garfinkel et al., 2015). In addition to that, however, the changes in one’s facial expression, posture, and voice can also be viewed as a form of physiological changes that happen during an anger response (Gross, 2015). They do not bear the same risks as the cardiovascular arousal.
It should be pointed out that the cardiovascular arousal, which is associated with anger, affects arterial baroreceptors. Baroreceptors are stretch-sensitive and are excited when a cardiac activity, for instance, blood pressure, increases; through these receptors, the changes in cardiovascular arousal affect the brain activity (Garfinkel et al., 2015). However, the analysis of Garfinkel et al. (2015) suggests that the role of baroreceptors is rather complex; it is capable of inhibiting cortical activity, but it is also evidenced to be connected to increased amygdala engagement. The authors conclude that baroreceptors can facilitate the processing of emotions, including anger, which is related to particular areas of the brain.
Areas of the Brain Associated with Anger
The areas of the brain which are associated with anger are the ones that are generally involved in the procession of emotions. Specifically, they include the “amygdala, insula, and prefrontal cortical (PFC) areas” (Alia-Klein et al., 2018, p. 2). Amygdala is shown to respond to negative arousal (Denson et al., 2014); furthermore, it is evidenced to be involved in blood pressure reactivity, as well as the insula (Garfinkel et al., 2015). The insula and PFC are typically described as being responsible for threat evaluation, as well as the assessment of emotional stimuli; additionally, the insula is engaged in processing negative emotions (Alia-Klein et al., 2018, p. 8). Furthermore, when people are asked to control their emotional response, their PFC reacts with enhanced activation (Bertsch et al., 2018). Also, it should be noted that there exists sufficient evidence to state that the dorsal anterior cingulate cortex (dACC) is a very significant part of anger processing: it is activated during anger response, especially in aggressive people, including those with anger-associated disorders (Denson et al., 2014; Kolla et al., 2017). Thus, several areas of the brain are involved in anger response.
Additionally, as reported by Alia-Klein et al. (2018) and Garfinkel et al. (2015), the areas of the brain that are engaged in the processing of visual stimuli can also be related to emotional processing. These areas are associated with the attention to particular stimuli (depending on their valence), which is of importance for anger. However, it should be noted that the topic of anger response and its association with the brain is still being researched (Denson et al., 2014). Therefore, the presented information can be expanded and adjusted in the future.
The Dual Effects of Anger
The impact that anger has on human cognition and behavior is multifaceted and difficult to predict because of it being understudied. However, the existing observations suggest that it is relatively unusual when compared to other negative emotions. Indeed, as a negative emotion, anger affects the way neutral stimuli are perceived (making them less likely to receive positive judgments) and can cause avoidance behaviors (Garfinkel et al., 2015). On the other hand, anger is viewed as an approach-related emotion (Alia-Klein et al., 2018), and it has the “motivating properties” that “facilitate behavior,” which, according to Garfinkel et al. (2015) are more characteristic of positive emotions. The same can be said about the “perceived task ease,” which is common for anger but would be more appropriate for a positive emotion (Garfinkel et al., 2015, p. 151). In other words, the effects of anger are “both facilitatory and impairing” (Garfinkel et al., 2015, p. 151). Additionally, there are context-related and individual differences that can have an impact on the effects of anger (Garfinkel et al., 2015; Gross, 2015). This feature of anger makes it unusual and unpredictable.
Emotional Regulation of Anger
Emotion regulation is defined by the presence of the “goal to influence emotion trajectory,” and it can be either conscious or unconscious while being aimed at regulating one’s own or another’s emotions (Gross, 2015, p. 5). Anger is a common target for emotional regulation because it is a negative emotion which, in certain cases, can lead to aggression (Alia-Klein et al., 2018; Denson et al., 2014; Hasler et al., 2017). All the processes that are aimed at changing the intensity, duration, or quality of one’s emotional response can be used to illustrate the notion of emotional regulation (Gross, 2015; Zimmermann & Iwanski, 2014). As classified by Gross (2015), examples include the avoidance of certain situations, situation modification, attention redirection, changes in situation reappraisal, and changes in the reaction to anger.
Certain brain activity can be described in connection with emotional regulation. In particular, it is once again associated with the prefrontal cortex, insula, and amygdala (Alia-Klein et al., 2018; Denson et al., 2014; Hasler et al., 2017). The topic is still being investigated, but an important area that is connected to anger control is the dorsal anterior cingulate cortex. It is evidenced to be engaged in cognitive-emotion control in challenging situations and is theorized to be responsible for the amount of control required (Denson et al., 2014, p. 1419). Based on recent research, it is shown to be more active in people with inherent aggression during the tasks that require anger control (Denson et al., 2014, p. 1423-1424). Thus, the brain areas that are associated with anger as such are also engaged in emotion regulation as related to anger.
Furthermore, the different types of emotional regulation are associated with different changes in the brain. Gross (2015) reports that most of them have not been studied yet, but there is still some evidence to discuss. For instance, the author states that distraction (attention regulation) and reappraisal reduce the activation of the emotion-associated brain areas (as named above), but suppression increases it. According to Gross (2015), the reappraisal approach is the most well-studied type of emotion regulation, and PFC seems to be crucial for it, even though the exact mechanisms of it enabling reappraisal are not clear yet.
It also noteworthy that emotion regulation differs in people depending on their age; the general tendency is the improvement of the ability to regulate one’s emotions (Gross, 2015; Zimmermann & Iwanski, 2014). This development can be associated with improved cognitive and executive functions, as well as increasing emotional intelligence (Zimmermann & Iwanski, 2014). Gross (2015) reports that infants are only capable of the simplest forms of emotion regulation; for instance, they can redirect their attention by shifting their eyes. With time, the use of language, the interaction with other people (especially family and peers), and the understanding of social rules assist children in practicing and learning emotion regulation. Throughout one’s adolescence and adulthood, emotional regulation proceeds to develop. Around 50, people tend to exhibit very strong emotion control and stability (Zimmermann & Iwanski, 2014). Thus, people learn to control their anger with age.
Furthermore, women and men show preferences for different types of emotion regulation. For instance, men are more likely to use suppression, and this approach is also often employed for anger (Zimmermann & Iwanski, 2014). Here, it should be noted that there are unhealthy types of emotional regulation, and suppression is one of them along with the use of different substances and food to change the emotional state. Suppression has been evidenced to worsen one’s memory (Gross, 2015). Additionally, Gross (2015) reports that suppression is ineffective in reducing negative emotions and can actually increase the response of the sympathetic nervous system (p. 9); moreover, it has been associated with increased risks for cardiovascular diseases (p. 19). Thus, the topic of emotional regulation is particularly important to investigate because it can provide the information about beneficial and effective methods of regulating one’s anger.
In turn, Gross (2015) reports that this knowledge can be used through emotion regulation interventions: it is possible to teach people healthy patterns of emotional regulation. Additionally, by targeting the people who are particularly prone to various negative emotions, it is possible to prevent the related negative outcomes. However, the author also notes that many of these interventions remain understudied and require the research aimed at determining their effectiveness. Overall, the topic of emotion regulation demonstrates the way anger research can be of use in practice.
Individual Variations in the Experience and Expression of Anger
Anger expression can be defined as a “high-arousal emotional reactivity to negatively valenced stimuli” (Alia-Klein et al., 2018, p. 1). For the expression of anger, PFC is especially important, as well as the insula, because the two regions are engaged in emotional expression (Alia-Klein et al., 2018; Denson et al., 2014). Anger expressions differ among people, and there are several reasons that have been proposed to explain such variations. First, it should be noted that the expression of anger is the result of an individual experience, which also varies depending on a person’s distinctive traits, health, gender, age, and circumstances (Deng et al., 2016). Among those, age is of particular interest: anger tends to be expressed more freely during the early stages of life with an increase during adolescence and without significant decreases during emergent adulthood (Zimmermann & Iwanski, 2014). However, in middle and older adulthood, people are less prone to expressing anger. Additionally, Zimmermann and Iwanski (2014) note that women may be more inclined to express anger, especially in emerging adulthood. The authors associate this development with the biological factors (for instance, changes during the adolescence period) and the growth of the emotion regulation ability.
Indeed, the differences in the expression of anger are also associated with the fact that there are differences in people’s ability to regulate emotions. Apart from those that are associated with age, there are individual variations in this skill, which are not sufficiently studied for conclusive explanations of their reasons (Gross, 2015). However, as pointed out by Gross (2015), they can be found in people since childhood, and they can include a tendency for the use of efficient or inefficient emotion regulation strategies (for instance, reappraisal versus suppression).
Varied emotional expressivity (and experiences) have been reported for different genders as well. Deng et al. (2016) highlight the fact that this tendency is found in some studies but is rebutted in other ones, which is why it is difficult to make any definitive conclusions. However, a recent investigation finds that the studied men were less expressive in response to anger while the women had less intense emotional experiences associated with it (for instance, their heart rate did not increase as dramatically) (Deng et al., 2016, p.9). The differences can be explained by different socialization and gender roles (Zimmermann & Iwanski, 2014). Thus, it is possible that the individual reactions to anger and its expressions are connected to one’s gender.
The so-called trait anger is another example of variation in anger expression: some people demonstrate greater aggression than other ones, and the severity of anger response may be associated with differences in brain responses. For example, the dACC is one of the areas of the brain that are associated with anger, and it is activated in different people to a different extent with stronger reactions being more characteristics of the people with high trait aggression (Denson et al., 2014). However, it is not entirely clear how trait anger works (Alia-Klein et al., 2018), and the topic is still under investigation.
Apart from the brain, genes can also explain some aspects of anger variation. Aggressiveness is a heritable trait that is associated with specific genes, including the monoamine oxidase-A gene. According to Denson et al. (2014), the topic is understudied, but it can be stated that the people who have the low-expression allele of the gene are more prone to anger-related aggression, and those with high-expression allele have the opposite tendency. A study by Denson et al. (2014) demonstrates that the differences in the alleles are also associated with the differences in the brain, in particular, in the dACC and amygdala, the activation of which was higher in the people with low-expression allele. This picture implies an increased negative arousal (amygdala) and increased effort at controlling it (dorsal anterior cingulate cortex). Moreover, the connectivity between the two was lower in high-expression adults, which implies that in low-expression people, the anger control processes are less efficient (Denson et al., 2014, p. 1423-1424). The authors explain that the changes may be associated with the role of the anterior cingulate cortex in anger control.
Denson et al. (2014) studied healthy men, but it should be noted that a similar mechanism that could explain the lack of anger control was found by Bertsch et al. (2018) in women with the borderline personality disorder (BPD). In particular, the authors investigated the neurological changes in healthy and BPD women who were asked to control their anger response and found that a negative coupling between the amygdala and dorsolateral PFC was characteristic for healthy women. Women with BPD did not have a similar brain activity, which can be used to explain the deficit in their ability to control anger. Bertsch et al. (2018) and Denson et al. (2014) demonstrate that deficits in the communication between the two regions are likely to be associated emotion control issues, especially when anger is concerned. Therefore, the differences in the functioning of the brain may be used to explain variation in anger expression.
In connection with the study of BPD, it should be mentioned that anger management can be difficult for people with specific disorders, which can cause the increased expressions of anger. Indeed, BPD is generally associated with difficulties in emotion control, which applies to anger among other things (Bertsch et al., 2018). Furthermore, people with attention deficit hyperactivity disorder (ADHD) are prone to mood changes and tend to be more impulsive than people without this condition; as a result, their anger expressions are sometimes very intense (Hasler et al., 2017). Similarly, people with addiction to cocaine exhibit increased anger expression (Alia-Klein et al., 2018), and the antisocial personality disorder is related to increased aggression, hostility, and anger (Kolla et al., 2017). In general, there are many health issues which may affect anger expression.
However, it should be noted that the disorders tend to be associated with certain differences in the brain. The BPD brain was shown to have connectivity deficiencies (Bertsch et al., 2018). In the case of ADHD, a particular “connectivity asymmetry pattern” along with certain variants of polymorphism markers of a gene (BAIAP2) could be the reason as indicated by the evidence collected by Hasler et al. (2017, p. 58). In particular, Hasler et al. (2017) report “abnormal functional activation” in the prefrontal cortex in people with ADHD, which may prevent other regions that are normally involved in emotional regulation from regular interaction (p. 59). Hasler et al. (2017) also note that the same gene that they have studied was found to be of importance for other disorders that are associated with anger. The authors suggest that the gene could be responsible for different brain development in people with said disorders. In summary, the examples of inherited aggressiveness and disorders demonstrate that differences in genotypes are associated with specific brain mechanisms that can explain the differences in anger control and, eventually, anger expressions.
Finally, there is some evidence which indicates that anger and aggression may also be influenced by biological clocks. A potential mechanism for this influence is again connected to genetics: some of the genes that are associated with anger are clock-controlled, and they, in turn, can affect the brain (Hood & Amir, 2018, p. 5). Furthermore, the disruption of biological rhythms (for instance, poor sleep) is shown to result in increased anger, aggression, and hostility, and Hood and Amir (2018) also demonstrate that the connection is two-sided: chronic anger tends to disrupt normal biological rhythms. Therefore, variation in anger can also be connected to biological clocks in more ways than one. Overall, it is apparent that different anger expressions in humans are connected to a large number of internal and external factors.
Conclusion
The present literature review offers a synthesis of recent evidence on anger, and the following conclusions can be made based on the results. Despite receiving notable attention from researchers, most of the topics associated with anger require additional research. Still, it is known that the common physiological change that occurs during an anger response is an increased cardiovascular activity. The latter affects baroreceptors which, in turn, are evidenced to influence the brain. It is generally accepted that certain parts of the brain, including PFC, amygdala, and insula are likely to be engaged in the processing, control, and expression of anger. The effects of anger are dual in that they include the typical negative-emotion ones (like avoidance) and positive-emotion ones (like behavior facilitation). The variation in anger expression and experiences can be explained by multiple factors; some of them, including mental health, may be associated with the effect of particular genes on brain activity. On the other hand, anger expression is also influenced by emotion regulation. Given the important role of anger in human lives and its association with multiple disorders and diseases (especially cardiovascular disease), the study of anger is of utmost relevance.
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