Vol. 6, No. 4, 2000 Page 2

Aggressive behavior, aggressive immune system?

A new study suggests that aggressive behavior is associated with a strong immune system, and that this association may be rooted in our genes.

Douglas Granger and colleagues analyzed data on 4415 men, aged 30 to 48 years, who were part of a Vietnam Experience Study. The researchers evaluated the subjects' childhood and adulthood aggression levels, testosterone levels, and measures of immune system functioning.

Granger et al. found that aggressive behavior was significantly correlated with five of the seven immune markers they studied. The relationship was curvilinear, with the most dramatic difference seen between men with moderate levels of aggressive behavior and those with very little aggressive behavior. The researchers also note, "These relationships remained strong even after statistically controllin ng for age, body mass, testosterone, health risk behavior (eg., tobacco, alcohol, and drug use and sexual promiscuity), physical illness (e.g., colds, injuries, trauma, sexually transmitted diseases, and general health symptoms), and depression," as well as post traumatic stress syndrome.

The aggression-immunity association was strongest for numbers of CD4 cells and B lymphocytes, which, the researchers note, "determine [to a large extent] the initiation, magnitude, and duration of specific cellular immune responses." They found no evidence that the relationship between aggression and immune function was mediated d by differences in testosterone levels.

A positive association between aggression and immune system function makes sense, Granger and colleagues say, from an evolutionary perspective. "Aggressiveness is vital for gaining access to females and food, protecting young, battling predators, and fighting [other] species over resources and territory," they note, all activities which promote survival. Conversely, they say, aggressive behavior increases the likelihood of injury and exposure to disease. Thus, a combination of aggressive behavior and strong immune system function could have bee en highly advantageous to early humans.

Their findings in human subjects, the researchers say, are consistent with primate studies showing that highly aggressive monkeys have higher lymphocyte counts than less aggressive monkeys.


"Human aggression and enumerative measures of immunity," Douglas A. Granger, Alan Booth, and David R. Johnson, Psychosomatic Medicine, Vol. of Biobehavioral Health, 315 Health and Human Development East, Pennsylvania State University, University Park, PA 16802.

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