It seems clear that Jared Loughner, the Arizona rampage shooter, was psychotic. As more information becomes available, it becomes possible to engage in a process of differential diagnosis. Was he a paranoid schizophrenic as some people have claimed? Or might another diagnosis make more sense?

There are reasons that weigh against the diagnosis of . First, people with this diagnosis tend to not have disorganized speech, inappropriate affect, and odd behavior. Apart from their , they are relatively intact and functional. In the case of Loughner, however, multiple people have reported on his convoluted speech, inappropriate , and bizarre public behavior.

In addition, paranoid typically have rigid delusions of being persecuted. This means that not only is there a plot or conspiracy, but it is directed against them. They are the ones who being followed, tormented, or . For example, Kimveer Gill (rampage school shooter in Montreal) posted messages online about the police having his house under surveillance for six years and Seung Hui Cho believed that people were trying to murder him. In the case of Loughner, he was preoccupied with a variety of conspiracy theories, but they were not directed at him. For example, he wrote about the United States government being the perpetrators of the September 11 attack and controlling people's minds through grammar, but he was not being singled out for persecution.

If Loughner is not a paranoid schizophrenic, is there another diagnosis that fits better? Though he might fit somewhere within the schizophrenic domain, his symptoms might better be explained by . If there is one word that sums up the essence of a person with schizotypal , it is "odd." They have odd thoughts, odd speech, odd behavior, and often an odd appearance. They are attracted to unusual ideas and tend to get lost in their bizarre beliefs. They are socially awkward and often paranoid. In addition, they often meet criteria for paranoid disorder. Their speech can be highly idiosyncratic and meandering, and they are prone to inappropriate expressions of emotion. All of this seems to fit what we know about Loughner.

Beyond trying to understand him through diagnosis, however, can we make sense of him by comparing him to other young rampage killers? Using school shooters as a comparison group, some similarities can be found. Loughner reportedly was unusually kind and well-behaved as a child. Similarly, Dylan Klebold was described as an unusually nonviolent child and Kimveer Gill was said to have been remarkably gentle in his youth. These killers were not antisocial or sadistic personalities throughout their lives, but experienced the onset of in their mid to late teens that led to violence.

A number of school shooters were attracted to Hitler and the ideology of Aryan supremacy, including Eric Harris, Marc Lepine, Kimveer Gill, and Steve Kazmierczak. Similarly, one of Loughner's favorite books was Hitler's Mein Kampf. Ideologies of superiority can be highly attractive for people who feel inferior.

It is also interesting that Loughner was rejected by the military. At least nine school shooters experienced military failure either by not being admitted or by being discharged shortly after entering the military. This is true of Robert Poulin, Marc Lepine, Kimveer Gill, Eric Houston, Jason Hoffman, Eric Pekka Auvinen, Matti Saari, and Steve Kazmierczak (see an earlier blog, "The Aspirations of Rampage Shooters," for more details, as well as "Expanding the Sample" and "Adult School Shooters" at www.schoolshooters.info). Perhaps the military represents manhood for youths who are struggling with a sense of , or perhaps they are looking for a socially acceptable means to pursue their fascination with weapons and violence.

In Loughner's case, it isn't clear that he had an obsession with weapons. In addition, his pursuit of a military career is interesting in light of his conspiracy theories about government. Perhaps his negative views of the government developed as a result of his rejection by the military. If so, this would be in keeping with paranoid personality disorder, symptoms of which include reading hidden meanings into innocuous events and holding onto grudges. In fact, this may be the reason he attacked Congresswoman Giffords. He had met her at a previous public event and asked her a question. He reportedly was put off by her answer. Perhaps he read secret meanings into this brief exchange. Even if he didn't, however, it may have been enough for him to develop a grudge that led to vengeance.

A final point: with all the focus on Loughner's mental instability, it is important to emphasize that mental problems--even psychosis--should never be assumed to indicate a risk of violence. The vast majority of people suffering from psychosis never become violent, and most violent people are not psychotic. When the two domains do come together, however, it can reinforce the stigma associated with psychological problems. Rather than letting this happen, we need to use this as an opportunity to educate the public.