KILLEEN, Texas -- This week's deadly shootings at Ft. Hood suggest that after years of trying to confront a mental health crisis, the military is still struggling to design a healthcare system that can identify and successfully treat service members who might become violent.
Army Spc. Ivan Lopez had been diagnosed with depression, anxiety and sleep disturbances and was being evaluated for post-traumatic stress disorder before he opened fire on fellow soldiers and then killed himself at Ft. Hood on Wednesday. Now the Army is confronted once again with possible correlations between mental health disorders and violence -- and how to screen for them.
Tens of thousands of veterans of the wars in Iraq and Afghanistan have been diagnosed with PTSD, but only a small minority commit violent acts. It is extremely difficult to predict those who are likely to explode into violence, according to experts in mass shootings and mental illness.
The disorder alone does not make a combat veteran or anyone else more prone to premeditated violence, experts say. But it can severely strain relationships or lead to a firing or demotion at work -- events that can push someone over the edge.
And some conditions associated with PTSD -- depression, anxiety, anger, substance abuse, suicidal thoughts -- are also associated with those who commit mass shootings.
"It's easy to identify possible predictors of a rare tragic event after the fact," Richard J. McNally, a psychology professor at Harvard University, said in an email interview. "It is much harder to predict it."
The 34-year-old Lopez had been examined by a psychiatrist last month and was prescribed Ambien, among other drugs, while undergoing evaluation for PTSD.
"We have very strong evidence that he had a medical history that indicates unstable psychiatric or psychological conditions," Army Lt. Gen. Mark Milley, the Ft. Hood commander, told reporters. Yet Lopez was not placed under any restrictions, according to the Army.
Several studies have found that combat veterans diagnosed with PTSD are two to three times more likely than other combat veterans to commit domestic violence or other violent acts, said Dr. Prakash Masand, a former Duke Univeristy psychiatrist who has studied the disorder.
"The absolute numbers are small, but the association is there," Masand said in an interview.
A study of 1,300 combat veterans by the medical school at the University of North Carolina at Chapel Hill found that 23% with PTSD or suffering from "high irritability" had been arrested for criminal offenses. Masand said the military fails to adequately follow up and monitor PTSD patients, using the same "one size fits all" treatment plan for those at high risk of violence and those who exhibit few risk factors.
Lopez, who had served in Iraq as a truck driver, did not see combat.
There were other signals, however. He bought the .45-caliber Smith & Wesson used in the shooting after his apartment was robbed, posting on Facebook how he now was "full of hatred." He also was angry that he had been granted less than two days to attend his mother's funeral in November, his family said.
On Wednesday, Lopez learned that the Army had denied his request for leave to attend to family matters in Puerto Rico, a federal law enforcement official told the Los Angeles Times on Friday.
PTSD can increase the likelihood of spontaneous aggression or violence, said Dr. Charles R. Marmar, chairman of the department of psychiatry at New York University Langone Medical Center: "It can cause outbursts when someone is provoked, but it does not provoke mass murder."
And according to Milley, an argument at Ft. Hood between Lopez and another soldier or soldiers may have provoked the shootings.
In the military, a diagnosis of PTSD is largely based on a service member's self-reporting. Because of the stigma associated with the disorder, many service members downplay any symptoms.
"We still don't have a simple test, like a pregnancy test or prostate cancer screening," to confirm PTSD, said Marmar. "We very heavily rely on the soldier to disclose symptoms and we rely on family members to corroborate them."
Those accused of mass shootings invariably are found afterward to have exhibited certain common "variables," said Ron Avi Astor, a professor of education and social work at the University of Southern California who has studied school shootings. These include expressions of intent, access to a firearm and friends and family members who heard the suspect mention the possibility of violence or suicide.