01/14/2013 01:15 pm ET Updated Mar 16, 2013

Diagnosing and Preventing the Unfathomable

Following a public act of unspeakable horror, like the shootings in Connecticut or Aurora, mental health professionals are asked to explain why or how a person could hurt others so profoundly. And then we are asked how to identify such people and prevent these violent acts.

Anyone who commits such horrific crimes is deranged in some way. What is little understood are the different kinds of disordered thinking and the different paths that lead to them. Although the perpetrators and circumstances of each tragedy are individual there are common features which separate them into distinct categories.

Those who suffer from a psychotic mental disorder are truly disconnected from reality and reach a point where they believe their delusions unquestioningly or experience hallucinations directing their behavior. These individuals -- who might include Jared Loughner in Arizona, and the Virginia Tech killer, Seung-Hui Cho -- are compelled by their psychotic symptoms to go out and kill.

A second group is defined by those who commit violence due to an irrational commitment to religious or political ideological beliefs, who might be the army psychiatrist, Nidal Malik Hasan at Fort Hood, the mass murderer of the Norwegian Workers' Youth League, Anders Breivik or Timothy McVeigh of the Oklahoma City bombing.

A third group of killers are those who lack control over their emotions and impulses, and commit crimes of passion or acts of hot-blooded revenge. These are people with a history of impulsive behavior as well as those who, in the heat of the moment or due to a unique set of circumstances, experience emotions that exceed their capacity for control.

All these are different from the fourth kind of killer, one who has an antisocial personality disorder, the socially disaffected loner with no conscience, moral constraints or consideration of what is right and wrong, as perhaps were the Olympic Park Bomber, Eric Rudolph, and the Beltway Sniper, John Allen Muhammad.

How do you distinguish among them? The way these cases end offers one clue. It's significant that the most obviously psychotic rarely kill themselves at the end of their shooting sprees. They don't know they have done anything wrong. Others, like Adam Lanza, in the recent Connecticut case, appear cognizant enough to understand that their lives are over once they are caught, and so do end their own lives.

These may seem like subtle distinctions. But in behavioral disorders, it is often subtle differences that allow us to accurately determine if destructive behavior is due to mental illness and, if so, diagnose and treat patients as early as possible in the course of their illnesses. We cannot predict exactly when or where mental illness will result in violence. However, we can identify risk factors to discern who has a greater potential for destructive behavior.

While psychotic symptoms, volatile emotions and impulsive behavior increase the potential for violence, the majority of floridly psychotic or deeply enraged people don't hurt others, and both conditions respond well to treatment with medication and specific forms of therapy. Identifying mentally ill people and providing accessible treatment is key to reducing violence.

The world would no doubt be safer if fewer people had easy access to automatic weapons. Registries of persons with criminal and mental illness histories have been proposed but are costly, questionably effective and, for mentally ill persons, discriminatory. What is abundantly clear is that our first line of defense against what just happened in Connecticut, and not that long ago in Colorado, Arizona and West Virginia, is a mental health care system that is pro-active, widely available and fully accessible.

The lowest-hanging fruit to prevent these mass shootings is the adoption of final rules for a bill that was passed and signed into law almost five years ago: the Mental Health Parity and Addictions Equity Act. The actual implementation of this law, combined with the anticipated effects of the Patient Protection and Affordable Care Act, would dramatically improve access to mental health care across the country, and in so doing lower the stigma that often prevents people who need help from seeking it, or sticking with treatment.

More and more, the system isn't failing to identify these patients, but rather failing to treat them. Jared Loughner, Seung-Hui Cho and James Holmes were young men who never completed, or in some cases received, treatment during or just after college -- many of these illnesses strike hardest in the late teens and early 20s -- and such transitions are often when patients are lost to the medical system. While there is still much to learn about the shooter in Connecticut, he appears to have engaged with care for a psychiatric or developmental disorder at some point, and then withdrew from it and from the world.

In the searing aftermath of these shootings comes the opportunity to take bold action. The debate over gun control may never end. But the debate over mental health parity and equal access to care ended some time ago. Let's put parity into effect now to improve the nation's mental health services and help to prevent further tragedies.

Jeffrey Lieberman, M.D. is Professor and Chair of Psychiatry at Columbia University and the President Elect of the American Psychiatric Association

For more by Jeffrey A. Lieberman, M.D., click here.

For more on mental health, click here.

For more healthy living health news, click here.