WASHINGTON -- When renowned sniper Chris Kyle was killed by a fellow veteran on Saturday, the news brought familiar headlines of the instability of returning warfighters and the dangers of post-traumatic stress disorder.

But health experts say that’s more Hollywood stereotype than reality, and that blaming veterans’ violence on their PTSD makes as much sense as blaming it on their broken leg.

“There is zero linkage between PTSD and criminal behavior,” said Barbara Van Dahlen, a clinical psychologist and founder of the veterans charity Give an Hour.

“We see veterans with PTSD who can become overwhelmed by a situation and may look to push back or push away. But that’s not the same thing as violent and aggressive behavior towards others.”

Researchers have established a link between traumatic stress disorders and a series of destructive behaviors: drug and alcohol abuse, self-cutting, suicide.

But the link between the disorder and violence toward others is much murkier, often connected only through secondary effects or compounding illnesses.

Police say that Kyle, a decorated former Navy SEAL and author of “American Sniper,” and his friend Chad Littlefield were killed by Eddie Ray Routh at a shooting range in Texas. Details are still in dispute, but Kyle was known to counsel veterans suffering from PTSD.

Routh served four years in the Marine Corps, including tours in Iraq and Haiti. Investigators said he had told police he suffered from PTSD but his arrest affidavit suggests that he might have murdered the men as part of a plan to steal a truck.

It’s unclear whether he has been diagnosed with the disorder. In a 911 call obtained by local media, Routh’s sister said he suffered from the illness and had received care recently in a mental hospital.

But most of the headlines in the days following the crime assumed that Routh had the condition.

CNN ran a story online asking whether veterans with mental illness should be permitted to have guns. NBC wrote a piece stating that the noise at shooting ranges can trigger panic responses in PTSD sufferers.

Up to one in five veterans returning from the recent wars could suffer from depression or some sort of post-traumatic stress, according to a 2008 Rand Corp. study. Despite the perception that mentally ill warriors pose a public health threat -- veterans derisively call it “the Rambo effect” -- research has shown only a tenuous link between PTSD and veterans committing violent, impulsive acts against others.

Federal researchers have identified 30 mass shootings in America since 1999. Of those, only four have involved veterans or military personnel. Of those, none of the shooters had been deployed to Iraq or Afghanistan.

A survey of nearly 1,400 Iraq and Afghanistan war veterans conducted by the University of North Carolina-Chapel Hill in 2010 found that servicemembers returning from deployment were more likely to lash out against others, with more than one in 10 threatening to use a weapon during a fight.

That study cited PTSD and combat exposure as possible factors in the violent behavior, but also blamed drug and alcohol misuse, domestic violence history, past criminal tendencies and immaturity of the veterans. A troubled history was more indicative of future problems than PTSD.

VA research has shown that divorce rates for veterans with PTSD are two times greater than those of other war veterans, and found that vets with PTSD have higher rates of physical and verbal abuse against their spouses.

Those researchers blamed the stress of dealing with the illness as a trigger for the violence, not the diagnosis itself.

In Time magazine this week, Dr. Elspeth Cameron Ritchie, a former Army psychiatrist, clarified the difference between an anxiety disorder and psychosis. The former can cause confusion, frustration and an inability to function, but does not affect the ability to tell right from wrong. The latter is a disassociation from reality.

But for many individuals unfamiliar with mental health illnesses, the distinction is lost.

In an editorial in USA Today this week, Health and Human Services Secretary Kathleen Sebelius wrote that only 3 percent to 5 percent of violent crimes are committed by people with a serious mental illness. But most Americans remain ignorant and fearful of the topic.

“Our first reaction is often not to reach out, but to turn away,” she wrote.

Van Dahlen said PTSD sufferers are more likely to withdraw from human interaction than strike out at strangers. She sees a bigger social danger in veterans who ignore or deny readjustment issues than those who seek treatment for mental illnesses.

“The ones who decide to ‘white knuckle’ it, whether because of denial or fear, they don’t talk to their families, they don’t seek help, and things get worse,” she said. “When they don’t acknowledge one problem, it can lead to more conditions later on.”

But news reports and public fear about “crazy war veterans” can dissuade veterans from seeking help, she said. Veterans advocates and VA officials have lamented that for years.

When Army veteran Wade Michael Page fatally shot six people and wounded four others in a mass shooting at a Sikh temple in Wisconsin last August, officials at Iraq and Afghanistan Veterans of America almost immediately fielded numerous interview requests about the long-term effects of war and PTSD.

But Page left the service in 1998 and never deployed overseas. The PTSD narrative was nothing more than a media assumption played out before most of the facts were made public.

The reasons behind the Kyle case might never be known. Routh is believed to be the only living witness of Kyle’s death. Police officials have had him on suicide watch since he was taken into custody.

In her analysis, Ritchie said it was too early to speculate on his motive. The crime could be connected to PTSD, or another mental illness, or drug abuse, or a number of other causes.

“Then again, the alleged killer simply could be evil,” she wrote. Twitter: @LeoShane

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