Shelley M. MacDermid, a Purdue University professor who served on a Defense Department mental-health task force last year, said typical PTSD rates among returning veterans were about 14 percent.
"Those are big numbers," she said of The Inquirer's Alpha findings.
National Guard and Reserve units, in general, have shown slightly higher PTSD rates than have regular Army units, she said.
The Defense Department task force said this might be in part because civilian-soldiers were separated after they returned home, rather than staying together as units in which the members could support one another.
Ira Katz, director of mental-health services for the Department of Veterans Affairs, said that among the 300,000 or so veterans who have been seen by the VA, about 20 percent have been diagnosed with PTSD.
But he said that twice that number - about 40 percent - have had some "mental condition."
"That's not all that different from your  percent," he said.
Both MacDermid and Katz said that PTSD had become a popular shorthand for all sorts of emotional symptoms that veterans experience. These may include depression and anxiety disorders, but not rise to the level of PTSD.
Steven Silver, who recently retired as director of the inpatient PTSD unit at the Coatesville VA hospital, predicted that as time went on, more and more combat veterans would be shown to have the high PTSD rate Alpha now shows.
PTSD, as a term, has been used only since 1980. World War II soldiers talked of battle fatigue. In World War I, it was shell shock.
Silver said that both the military and the VA had become more aggressive in warning troops about PTSD and getting them treatment.
He said that although Alpha's rate was high, "in some ways, it's good news. It means that people are coming in for help."
PTSD typically is treated with psychotherapy and antidepressant drugs, including Zoloft and Paxil.
About two-thirds of Alpha veterans have received care at VA hospitals and clinics - for PTSD, physical ailments, or both.
Of those who expressed an opinion, 57 said they were satisfied with VA care and 19 said they were not.
Contact staff writer Tom Infield at 610-313-8205 or firstname.lastname@example.org.