The horrifying theater massacre in Aurora CO by James Holmes has re-energized the debates over gun control and mental health and criminal culpability. It is possible, however, that these debates miss the more fundamental issue of which Holmes mass murders are illustrative. Social scientists have known for fifty years that America, and other advanced societies, have a "young male problem." It is a set of statistical facts that young males, aged 18 to 30 years, in great disporportion, commit felonious violence. Murder, homicide by DUI, extreme violence against women, and gang violence are all disproportionately committed by young males. In California, for example, in 2008, 80% of DUI offenses were by young males, average age 30 years; we can infer that most of the 1,400 DUI-related homicides of the 3,400 persons who died in California* were killed by young male offenders. Similarly, tit-for-tat gang murders are also largely the product of young male gang members. Over 16,000 thousand homicides are committed each year in the US, over 11,000 by firearms,^ disproportionately by young males, but with one or two or three victims, and so lack the spectacular horror that brings national news attention. The dead victims are dead victims, whether by mass random murder or drive-by shootings or in gang warfare.
The role of testosterone is implicated by the age category. Ages 18 to 30 are peak years of testosterone. After age 30, testosterone diminishes sufficiently that young men calm down considerably, as reflected in statistics of violent crimes. (I don't mean to prejudge the issue as excessive testosterone; lower level of testosterone could lead to violence was over-compensation, I suppose.)
Juveniles, females, and older persons do not commit murders and homicides in proportion to their representation in the total population. The statistical relationships between young males and murder and homicide are easy to follow. For instance, those crimes increased dramatically in the major Texas cities after young men from New Orleans relocated there after Katrina decimated their home city. The problem of young male violence appears in other societies, including those with strict gun prohibition or controls. (I am not citing as evidence, but note as interesting related fact that Islamist terror suicide bombing is overwhelmingly commited by young men.)
There are other social indicators that point to some young males as a problem category; for instance, chronic users of marijuana, defined as imbibing twice a week or more, are 75 per cent young males.
Most young males are not criminals and their ascent to adulthood is not problematic; to the contrary, their idealism, work, and often military service are an honor to our nation. But a significant portion of young males are problems for their proclivity to felonious violence. What is the source of their problem? This has been a much studied matter, but I would like to offer this direction for discussion: socialization of testosterone.
Testosterone is an explosive hormone and any observer of adolescents can testify to the great efforts made by society to teach young men how to direct its energies (e.g, in competitive sports, in military training) and control behavior (e.g., respect for women, awareness of consequences of thoughtless violence). Here is a major social preoccupation whose success and failure has great consequences for young men.
Putting the young male problem in this context relieves it of the gun control and mental health debates. For this subset of young males, extreme violence is not controllable by preventing them from having guns, driver's licenses, or alcohol. When sequestered in prison, denied all guns, licenses, and alcohol, violence by young males is still widespread.
The issue is to define more carefully the relationship between testosterone (and testosterone levels and associated hormones) and behavior, differentiate the category more finely so we understand why some men handle the eruptive force of testosterone better than others, and determine how institutions of its socialization (e.g., family) succeed and fail.