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Is Testosterone the Hormone Behind Aggressive Behavior?

“The world needs less testosterone”.

Testosterone Behind Aggressive BehaviorWhat is meant by this ever-popular cliche? Obviously, not literally the male hormone. Aggression, violence, hostility - and, on a larger scale, cut-throat competition, crime, and military conflicts. Ever since testosterone was identified by medical science, every essentially masculine flaw of character and behavior has been attributed to the overflow of the ‘male’ hormone. After all, isn’t it testosterone that makes men - well, men, with their tendency to compete, dominate, and display aggression?

Apparently, not. Shocking as it may sound, the blamed-for-everything hormone can be the source of quite the opposite emotions and behaviors: calmness, friendliness, and a more positive attitude. A research study by Dr. Christina Wang at the University of California proves that.

Having studied a group of 54 testosterone-deficient men, whose testosterone levels were low for various reasons, researchers have concluded that it is the lack of the hormone that causes all the negative emotions, rather than its abundance. The hypogonadic men complained of irritability and anger, and experienced a serious improvement in their mood after several months of testosterone replacement therapy. With all the testosterone-related stereotypes, it is hard to believe that men receiving testosterone actually started feeling calmer and happier.

Another study by Dr. Bremner and his colleagues was aimed at identifying the effect of decreased testosterone on libido. In the course of the study, men were artificially brought to hypogonadic state, and reported an increase in aggression while in that state. It is unclear whether that increase was directly linked to the hormone level or caused by the overall frustration and lack of energy that low testosterone is associated with. However, it became obvious that it is a decrease in testosterone that can cause aggression, not an increase in it.

Why Has Testosterone Always Been Associated with Aggression?

To some extent, testosterone being associated with brutal behavior is explained by the fact that men, who are more prone to such behavior, have much more of the hormone than women do. While a normal testosterone level for a woman is around 40 nanograms per deciliter of blood, men have about ten times of that amount. So, it’s easy to link the concentration of testosterone with more aggressive behavior, even though this link is merely speculation.

Some studies support this assumption, too. For example, both male and female laboratory animals, injected with testosterone, exhibited aggression and were more likely to attack other animals. Studies of prisoners and other groups, seen as prone to violence and hostility, revealed increased levels of testosterone in aggressive men. But do these results really prove the direct link between testosterone and aggression?

Perhaps It’s Not About Testosterone, After All

The assumption that testosterone causes aggression, because lab animals exhibited it when their testosterone was increased, is often called into question. Scientists are unsure that studies of animal behavior can produce results, immediately relevant to human emotions. Besides, the injections could have a variety of subsidiary effects, and it could be these effects that triggered aggressive behavior rather than the increase of testosterone in the blood.

As for the human studies of prisoners, the results are also contradictory. Prisoners are definitely under a lot of stress, and stress can influence hormone levels and behavior in ways that are not fully understood.

Estrogen Equals Aggression?

With all the male and female stereotypes, ‘female’ hormone estrogen has hardly ever been accused of triggering aggression, but several studies show there may be a link. A study at Pennsylvania State University compared the effects of estrogen therapy on girls who suffered from a delay in sexual maturity and testosterone therapy on boys with a similar condition. In the course of the study, girls displayed earlier and more severe outbursts of aggression than boys did.

Scientists suggest that it can be estrogen, not testosterone, that is responsible for hostile behavior in teenagers. In male bodies, testosterone is converted to estrogen, which is why the boys in the above mentioned study started displaying aggressive behavior later than the girls, who received estrogen directly.

Another study by Dr. Donald W. Pfaff and his colleagues further studied the link between estrogen receptors and aggressive behavior. Genetically altered male mice that lacked estrogen receptors exhibited behavior, unusual for their sex: they were hardly likely to attack intruders and all in all behaved less violently.

The results of the various studies can be interpreted differently, but one thing seems unquestionable: testosterone equals aggression is nothing more than a stereotype. The mechanisms behind violent behavior are much more complex than that, so it is time to get rid of the testosterone-related cliches when speaking about competition or hostility.