Variation in Dopamine and Cortisol Levels in the Hypothalamic Pituitary Adrenal axis and their Association with Pediatric

Aggression

Review

BIOL 3095

Gustavo A. Martínez-Muñiz

Abstract:

The Hypothalamic Pituitary Adrenal (HPA) axis is the part of the brain that controls the reactions to stress of the body. The hormones these axes secrete are greatly involved in the control of the behavior of the person. Any changes in the levels of hormones affect the behavior of a person and the way in which they respond to stress in society. This paper focuses on the responses of the human body and mind to behavior involving low levels of cortisol and dopamine, which are produced by the HPA axis. In previous studies and papers it is shown that low levels of cortisol are strongly associated with aggressive behavior, be it impulsive or predatory.

Introduction:

Cortisol and dopamine are two different hormones produced in the Hypothalamic Pituitary Adrenal (or HPA) axis in the human brain. The HPA axis is what links the central nervous system with the peripheral response system. These hormones are greatly involved in the control of behavior and impulses in the human body, along with its emotions. These hormones, found in varying levels throughout the body, are involved in different reactions to stress, which can result in aggression in children. These results can be associated with psychiatric disorders such as Attention-Deficit or Hyperactivity

Disorder (ADHD) or Post-traumatic stress disorder (PTSD). All of these disorders are classified as pathologic types of aggression in minors. Future expectations for this paper would be to develop new foundations on reasons for pediatric aggression in order to give proper treatment to patients with pathologic aggression.

Cortisol levels in the HPA axis:

Pathologic aggression is classified as either physical or verbal aggression. Physical aggression is divided into four subtypes: impulsive, reactive, predatory, and premeditated aggression. Impulsive and reactive aggression are the types of

aggression that are reactions to stress or stimuli. These types of aggression are normally responses to intimidation or attacks. Meanwhile, the predatory and premeditated are the types of aggression that are actually planned before-hand, and are usually directed towards peers.

These four types of physical aggression are common in psychiatric disorders. Physical aggression combined with verbal aggression, are commonly found in children or teenagers who abuse their peers. They are what is referred to bullies.

Verbal aggression can occur in two ways. The aggressor uses verbal abuse to intimidate or exclude his peers. Examples like this are spreading rumors about a peer. The second way is using verbal aggression to affect one’s self with his or her own words.

Studies have been done to study the effects of abnormal or deficient levels of these hormones in children and teenagers. Further studies have been done to measure the various levels of either cortisol or dopamine that are either absent or excessive in teenagers and children to determine the treatment of such behavior for healthy functioning in a social environment. In one specific study, Van den Bergh B. et al (2008), indicate that different measures of cortisol were taken at different times of day in order to measure if varying daily levels of cortisol affect aggression.

This study involved the observation of a group of 58 adolescents with self-reported characteristics of aggressive behavior, trait anxiety, and depressed mood

symptoms. Cortisol was measured from the saliva samples of the teenagers at three different points of the day. Flattened diurnal cortisol levels, according to the results of this study, showed that there was no heightened aggression in the teenagers, though it was associated with the other two symptoms. In other words, low levels of cortisol can be more strongly associated with depressive mood and trait anxiety symptoms than aggressive behavior.

Lopez-Duran N. et al (2009), studied a group of 73 children who were considered to be proactively or reactively aggressive, and they associated that aggressiveness to the HPA axis. It is the main regulator of stress in the human body. According to the article, proactive aggression is the same as predatory or premeditated aggression, whereas reactive aggression is similar to impulsive aggression. In the study, the children were put through a series of fear-inducing or frustrating stress tasks, and afterwards a sample of their saliva was taken to measure the levels of cortisol that they had in their systems after being scared or frustrated. Several samples of saliva were taken before and after being put through the task, as well. The results of this study showed that the children who were exposed to stress or fear-inducing tests had lower levels of cortisol during the time closer to the exposure to stress or fear. This would indicate that aggressiveness would be higher when the children were exposed to stress, and that the child with reactive aggression would have a stronger relation to the HPA axis than a child shown to be proactively aggressive.

Moreover, both of these studies show that low cortisol profiles can be associated with different types of aggressive behavior, indicating that in order to treat the disorders that a child or a teenager were diagnosed with, cortisol is a hormone of interest to measure in order to make a proper diagnosis and treatment.

Internalizing vs. Externalizing Behaviors and Cortisol

A study by Ruttle and associates (2011) observes the association of fluctuating levels of cortisol with either internalizing or externalizing behavior. Internalizing behavior are those that direct the results of stressful situations to self. An example of this form of behavior is clinical depression. Externalizing behaviors are those that respond towards others rather than self in an aggressive manner.

The study was throughout the growth of 96 youths and measuring cortisol from 20 daily samples of saliva. These samples were taken throughout the late years of youth and the early adolescence.

The results of the study showed that children and adolescents with internalizing behaviors were shown to have more flattened diurnal cortisol profiles. Whereas the morning cortisol level had no strong association with the youths exhibiting externalizing behaviors; indicating that behavior problems in children and adolescents can be linked to the abnormalities in the quantities of cortisol that are produced during the morning for the patients that express these kinds of behaviors. This would imply that the HPA

axis in the children or adolescents that have these kind of behaviors or personality changes have a blunted HPA axis. This means that the HPA axis would not produce the necessary amount of cortisol in the morning.

A blunted HPA axis would then be an important factor to study when observing aggressive or depressive behavior in adolescents. Further studies involving a blunted HPA axis would be to observe what factor would be the one that inhibits the production of hormones, and whether or not it is possible to stimulate the production of the hormones.

Psychological observations on aggressive behavior

Observing how aggressive behavior is prevalent in social activities and environments, it is an important point that must be taken into consideration. In a study , Hemphill et al. (2010), conducted a survey in the states of Washington, USA, and Victoria, Australia. The survey consisted of interviewing students in the fifth, seventh, and ninth grades. The purpose of the survey was to observe how many students were capable of attacking a peer either physically or verbally, in order to make that peer be unaccepted in the school or look bad in front of the rest of the schoolmates. The results of the survey showed that boys were more capable of any type of predatory or verbal aggression than females, and that different stages of puberty were also associated with the level of aggression in the student. Other factors that were taken into account were the sociability of the student, drug and alcohol

abuse, and the state of their homes (economic state of their parents, whether they lived with both parents, one, or neither, etc), and the types of friends the students had in and out of school.

Some factors that could not be observed in this survey were the hormonal levels in the students, in order to not be invasive.

Association of Dopamine in the HPA axis

Barzman et al. (2010), states that low cortisol levels in the HPA axis can be associated to aggressive behavior, and that pre-pubertal children with disruptive behaviors would have low cortisol levels when exposed to stress-inducing trials or situations. Low cortisol is also associated with aggression patterns and early aggression developed in male children. The authors state as well that abnormal levels of a major dopamine metabolite, homovanillic acid are associated with high levels of aggression in grown males, especially those convicted of murder. The same levels of the metabolite are found to be associated with aggressiveness and comorbid ADHD in children.

Conclusion:

This review paper emphasizes the importance of observing the levels of cortisol and dopamine in children in order to diagnose and treat the pathological aggression that has been observed in patients. Contextualizing these behaviors with every day scenarios is also important in order to identify what factors in the patients’

lives are the ones that are triggering the stress causing the aggression. All this will lead to improving the treatment of pediatric aggression in psychiatric disorders and in minors who attack their peers either verbally or physically.

An important possibility of working in the future would be to combine the psychological survey with the measurements of hormones of the HPA axis. It may possibly aid in determining directly what environmental factors are the ones that cause minors to be aggressive, either towards peers or themselves. Though in the studies by Lopez-Duran et al. and Van den Bergh et al. there were surveys, they were not as in deep as the survey performed by Hemphill et al. Such a survey goes deeper into the reasons why the minors behaves aggressively and can help associate that behavior with the either low or high levels of hormones.

As observed in the study conducted by Ruttle et al. (2011), a blunted HPA axis indicates a low production of hormones. If studies cannot take place to study the stimulation of hormone production, then the patients would be studied to observe what would be the amount of cortisol they would need to function normally in society, and afterwards, the hormones would be supplied to them in the form of a medication or treatment that will allow them to have the hormones they need.

It is important for people to remember that science is now opening doors of knowledge. This would indicate that what was once improper behavior now can be identified as a biological disorder or disease

that can and must be treated in order for the person to function properly in society. However, treatment is only part of the solution. Understanding on behalf of those people the patient socializes with and lives with is an important factor in completely

understanding and helping the behavior and condition of an aggressive child or person. It befalls not only on the patient, but those around him or her as well, to help lead a healthy and normal life.

References:

Barzman DH, Patel A, Sonnier L, Strawn JR. 2010. Neuroendocrine aspects of pediatric aggression: Can hormone measures be clinically useful?. Neuropsychiatric Disease and Treatment 2010:6 691 – 697

Hemphill SA, Kotevski A, Herrenkohl, Toumbourou JW, Carlin JB, Catalano RF, Patton GC. 2010. Pubertal stage and the prevalence of violence and social relational aggression. Pediatrics. 2010 August ; 126(2): e298–e305. doi:10.1542/peds.2009-0574.

Lopez-Duran NL, Olson SL, Hajal NJ, Felt BT, Vázquez DM. 2009. Hypothalamic Pituitary Adrenal Axis Functioning in Reactive and Proactive Aggression in Children. J Abnorm Child Psychol (2009) 37:169–182

DOI 10.1007/s10802-008-9263-3.Van den Bergh BRH, Van Calster B,

Pinna Puissant S, Van Huffel S. 2008. Self-reported symptoms of depressed mood, trait anxiety, and aggressive behavior in post-pubertal adolescents: Association with diurnal cortisol profiles. Hormones and Behavior 54 (2008) 258-257

Ruttle P, Shirtcliff E, Serbin L, Fisher D, Stack D, Schwartzman A. Disentangling psychobiological mechanisms underlying internalizing and externalizing behaviors in youth: Longitudinal and

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