Researchers have discovered a there is a genetic link between personality and mental illness. As one of the researchers explained: “Mental illnesses can be viewed as maladaptive or extreme variants of personality traits.” The researchers studied the genetic profiles of 260,000 people focusing on the five long-established personality traits (extraversion, neuroticism, agreeableness, openness to experience and conscientiousness) that are considered the basic categories of personality. What the researchers found was that these personality dimensions when identified on a person’s genome map (yes, there are “personality genes”) strongly correlated to gene variations that predicted various mental illnesses.

Now you might say, “What’s new?” It is observable in our everyday life that people we know who have, for example, a neurotic personality also tend to have anxiety disorders and depression. These links between personality and mental illness have long been observed and studied. What this study reveals however is that there is a genetic link; in other words, it’s not all nurture. The researchers theorize that the personality a person is born with may tip over into mental illness when pushed to extremes by life experiences.

This field of research, which is sure to eventually unlock the keys to mental illness, is a potential minefield in terms of the criminal justice system. It would not be a stretch to say that many criminals are born. In other words, a criminal is born with a certain personality type—as are we all— but the criminal personality is one susceptible to the risk of mental illnesses, such as antisocial disorders or psychopathy. Indeed, it is estimated that more than half of all incarcerated criminals have some kind of mental illness. (Removing the large numbers of persons incarcerated for victimless crimes would increase that percentage substantially.)

The aforementioned study that found a genetic link between personality and mental illness may explain the making of a criminal. Not all people who are born with personalities susceptible to mental illness actually become mentally ill, but as the researchers theorized, adverse life experiences may tip that personality into mental illness. Many criminals are not only mentally ill but they also had very difficult childhoods and, as studies have repeatedly shown, many were abused as children.

How will we treat our criminal populations when and if a definitive genetic link to criminality is established? (I believe that very soon in the future there will be no doubt that some criminality has a genetic component.) If criminality (or let’s say, some criminality) is genetic, a thinking and compassionate society could no longer insist that the criminal necessarily committed his or her crime as a free agent. But nor can society excuse criminal behavior. Perhaps in the future, we can identify the at-risk personality and intercede to mitigate adverse life experiences. Of course, that comes with some serious privacy concerns. Perhaps the best we could do is recognize the genetic component and address the behavior with that understanding. Or maybe, in our brave new world, the offending genes will be manipulated in a way to neutralize the risk of mental illness.

With almost 25 years experience in criminal defense, William Weinberg is available to consult with you regarding any criminal matter. You can reach him at his Irvine office at 949-474-8008 or email him at