The Times Square bomber Faisal Shahzad and Fort Hood shooter Major Malik Nadal Hasan (and many other religious extremist killers, including Scott Roeder, who shot abortion provider Dr. George Tiller) bring up a core question that hasn't been fully addressed by the field of psychiatry or law. When do rigid and extreme "spiritual" views and acts cease to be an expression of religious fervor and actually constitute mental illness? When does an unwavering and extreme interpretation of scripture of one kind or another cross the line from "faith" to delusional thinking-as in, psychosis.

Is it possible that Shahzad or Nadal and others have become killers when mental illness has expressed itself as a bizarre acceleration and perversion of their underlying spiritual beliefs?

This is very complicated territory to discuss, because we are understandably very reluctant to paint any firm belief in a religious idea as "crazy." The last thing we want is for one group to paint those who believe in an afterlife or reincarnation or the Resurrection or the parting of the Red Sea or God telling Abraham to sacrifice his son Isaac as "insane."

And yet, psychiatrists know that a significant percentage of patients who fall victim to psychiatric disorders that include fixed and false beliefs (delusions) don't talk about the CIA following them or extraterrestrials visiting them, they talk about being "chosen" by God for special missions or being told by God to fast or actually being God.

Religious delusions can afflict those who have expressed no prior deep religious faith or they can befall those who are practicing Muslims or Christians or Jews. I remember one man whose first episode of mental illness included arriving at the ER carrying a statue of the Virgin Mary, which he had stolen from a local church, believing he was receiving messages from her.

These questions about psychosis masquerading as faith or commandeering underlying faith and turning it rancid and violent are particularly important when we consider that Shahzad and Nadal were both men who had experienced psychological turmoil and may have been depressed.

Delusions dosometimes occur in the setting of depression. Yet, spiritual awakenings can occur at moments of desperation, too. And this is the tremendously difficult terrain we walk when we bring up the question of when religious beliefs cross the line into psychiatric symptoms.

When a man experiences a series of losses that causes his mood to plummet and his mind to shift focus from family and work to believing he is on a mission from God to battle infidels, is that a time to lock that man in a psychiatric unit before he ends up harming others? If he does harm others, is it right to execute him when he might be ill, rather than evil?

If someone even begins to plot an act of violence based on a religious belief that tips into delusion, is it fair to hold that person indefinitely (possibly, forever) in a psychiatric facility? Is it fair and legal to involuntarily treat that person with antipsychotic medications as an outpatient (perhaps for the rest of his life?)

This blog won't end with the answers. I believe, however, we should be asking these questions, and similar ones, as part of our strategy to prevent violence and terrorism perpetrated in the name of one religion or another.

Here is one possible place to begin: What if we were to agree that religious beliefs that become extreme and include the idea that others should be destroyed for their evil constitute psychosis? Could we educate mosques and churches and temples to bring to psychiatric attention those members of their communities who display those symptoms?

Dr. Keith Ablow is a psychiatry correspondent for Fox News Channel and a New York Times bestselling author. His book, "Living the Truth: Transform Your Life Through the Power of Insight and Honesty" has launched a new self-help movement including www.livingthetruth.com. Dr. Ablow can be reached at info@keithablow.com.

Dr. Keith Ablow is a psychiatrist and member of the Fox News Medical A-Team.