angrier testosterone

Does Testosterone Make You Angrier?

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The many anabolic properties of testosterone are well researched and have been well documented with respects to strength training and muscle hypertrophy. However, the potential impact that testosterone has on male behavior, and to a lesser extent female behavior, has not been as clearly defined. Numerous studies have successfully identified a direct causal link between testosterone levels and aggressive behaviors in animals; in humans, though this notion is not as clear-cut, and the issue remains open to debate.

Testosterone is the primary sex hormone in males, and thus it plays a key role in the development of the male reproductive systems as well as promoting all the secondary sexual characteristics. Testosterone also works as a steroidal androgen, which allows it to increase the amount of protein found within the cells of the skeletal muscles and thus it can be used to enhance physical performance. It is because of this intimate relationship to mostly male characteristics that testosterone came to be associated with aggression and aggressive behaviors.

TESTOSTERONE PROMOTES AGGRESSIVE BEHAVIOR

Some of the initial scientific studies done on the subject of aggression as a result of the presence of testosterone were done on mice. In 1987, in a study published in the Hormones and Behavior and conducted by Van Oortmerssen, et al., found that mice are more likely to attack when plasma testosterone levels were higher. Similar studies done on female mice concluded that there was a definite causal link between the presence of plasma testosterone and overtly aggressive behaviors. Female mice, starting at 120 days of age, were given injections of testosterone for seven consecutive days and demonstrated aggressive behavior on a level comparable to that of males.

Further evidence to suggest hormones are intricately linked to behavioral patterns can be noted in the marked decrease of aggressive behaviors displayed by castrated animals of countless species. In this animals when testosterone is reintroduced into the organism through replacement therapies pre-castration levels of aggressiveness return. This presents an excellent model for the role of testosterone in aggressive behaviors. However, all this evidence is based on animal studies; so what is the purpose of testosterone in human aggression?

HUMAN AGGRESSION

Aggression serves an evolutionary function regarding enhancing survival mechanisms as well as boosting procreation chances. In other words, when resources are limited, be they food or mates, competition arises, and therefore individuals must compete to increase their chances of survival. Seen in this light, aggression becomes an advantage.

Hormonal modulation of behavior can be described for example; in the way that testosterone acts on serotonergic synapses and lowers the amount of 5-hydroxytryptamine receptors available for transmission. This is important because the presence of 5-hydroxytryptamine receptors aids in the inhibition of aggression. However, hormones alone cannot be wholly responsible for behavioral aggression. There is, after all, a significant percentage of the male population that does not behave in overtly aggressive ways. Although hormones can facilitate or inhibit the development of specific behaviors, there must be other factors at play.

THEORIES OF AGGRESSION

There are two main theories that correlate the role of testosterone in aggressive behaviors. The first one is the Challenge Hypothesis of Aggression. The Challenge Hypothesis predicts that plasma testosterone levels rise at puberty to facilitate direct competitive behavior between reproductive rivals. The fact that testosterone levels are lower in fathers than in non-fathers seems to support this theory, but this hypothesis has not been thoroughly challenged in human behavior.

The second theory is known as the Evolutionary Neuro-Androgenic Theory of Male Aggression”. This theory states that testosterone has evolved to aggressively promote a competitive brain even to the point of risks of harm becomes apparent. Individuals with masculinized and competitive brains are then able to adapt better, survive, and procreate as often as possible.

So even though testosterone plays an important role in aggressive behaviors, it does so in a sociologically beneficial way. It would be unwise, and borderline irresponsible, to promote that testosterone induces overtly aggressive behaviors as there is no evidence to back this up. The myth of out of control testosterone aggression is most likely tied to societal views on gender. Remember the experiments done on female mice? There was a similar experiment that injected the female mice with estrogen, and the results were identical. Female mice with higher plasma levels of estrogen fought more aggressively as well, but perhaps, because these findings do not conform to the societal norm of the aggressive male, they went unnoticed.

 

 

REFERENCES:

  • Olweus, Dan, et al. “Testosterone, aggression, physical, and personality dimensions in normal adolescent males.” Psychosomatic medicine (1980).
  • Mehta, Pranjal H., and Jennifer Beer. “Neural mechanisms of the testosterone–aggression relation: the role of orbitofrontal cortex.” Journal of cognitive neuroscience10 (2010): 2357-2368.
  • Björkqvist, Kaj. “Sex differences in physical, verbal, and indirect aggression: A review of recent research.” Sex roles3-4 (1994): 177-188.
  • Wingfield, J. C., et al. “Testosterone, aggression and communication: ecological bases of endocrine phenomena.” The design of animal communication. MIT Press, Cambridge (1999): 255-284.
  • Dabbs, J. M. “Testosterone, aggression, and delinquency.” Pharmacology, biology, and clinical applications of androgens. New York: Wiley-Liss. p (1996): 179-190.
  • Olweus, Dan, et al. “Testosterone, aggression, physical, and personality dimensions in normal adolescent males.” Psychosomatic medicine (1980).
  • Archer, John. “The influence of testosterone on human aggression.” British journal of psychology1 (1991): 1-28.
  • Eisenegger, Christoph, et al. “Prejudice and truth about the effect of testosterone on human bargaining behaviour.” Nature7279 (2010): 356.
  • Mazur, Allan, and Alan Booth. “Testosterone and dominance in men.” Behavioral and brain sciences3 (1998): 353-363.
  • Bjorkqvist, Kaj, et al. “Testosterone intake and aggressiveness: Real effect or anticipation?.” Aggressive Behavior1 (1994): 17-26.
  • Layton, J. Bradley, et al. “Comparative safety of testosterone dosage forms.” JAMA internal medicine7 (2015): 1187-1196.
  • Van Oortmerssen, G. A., D. J. Dijk, and T. Schuurman. “Studies in wild house mice II. Testosterone and aggression.” Hormones and behavior2 (1987): 139-152.

 

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