Andreas Maercker of the University of Zurich and Leipzig University's Elmar Braehler surveyed 2,400 men and women of all age groups for the nationwide study on the effects of traumatic experiences.

Extrapolating their results, they concluded that 2.3 percent of all Germans, or 1.8 million people, were affected by some sort of serious trauma. But they were surprised by the relatively high incidence of post-traumatic stress disorder (PTSD) among older people in Germany.

The researchers said that, while studies of PTSD in other countries, such as the United States and Canada, have shown older people tend to have lower instances of the disorder, the German study shows the opposite.

"To our surprise, PTSD among the 60- to 95-year-olds is three times as high as in the younger age groups, Maercker told reporters on Monday, May 19.

Braehler said that almost all the older Germans who reported suffering from the symptoms of PTSD were affected by a traumatic experience during World War II.

Symptoms are often misdiagnosed

"Those affected talked about suffering panic attacks if they hear a fire truck responding to an emergency because they lived through aerial bomb attacks as small children," he said.

Maercker added that many of those affected spoke of how "the pictures come back" of traumas like the loss of a sibling or schoolmate, or seeing their childhood home be destroyed by bombs. The survivors also reported having feelings of guilt. Their symptoms have often been wrongly diagnosed as depression, the University of Zurich expert said.

He added that PTSD often manifests itself once people enter retirement and have the time to take stock of their lives.

"Then, the PTSD sets in," Braehler said.