Veterans Day is a time to honor this nation's servicemen and women.

But the reminder of wartime experiences can also lead to bouts of anxiety in veterans who suffer from post-traumatic stress disorder.

Any event related to the trauma that caused the disorder can trigger its symptoms, said Joseph Boscarino, a senior investigator with the Geisinger Center for Health Research.

Boscarino, a Vietnam veteran, urges returning veterans' families to watch for risky behaviors or substance abuse, which can be symptoms of PTSD.

"The family members notice they're dysfunctional. They're not working, they're not enjoying life, they're still in a tank in Iraq," he said. "Or they're still ... fill in the blank. That's the first thing they notice. Trauma is still a part of their life."

Individuals suffering from PTSD have higher rates of drug and alcohol abuse, Boscarino said.

The disorder affects more than five percent of the U.S. population. But the rate among combat veterans can be much higher -- one study from last year suggests rates as high as 16 percent.