Post-traumatic stress disorder does not only occur in soldiers deployed in Afghanistan immediately following their return home, but the condition showed a spike of recurrence five years later, a study in the Netherlands has found.

The finding that both new and recurring cases of PTSD could emerge many years later suggests veterans should be screened for longer than just the usual one or two years after they returned home, the study authors propose.

"Our objective was to gain more insight in the changes in posttraumatic stress complaints in a long-term period after deployment, ultimately to evaluate the timing of an increase in treatment demand after deployment," said Iris Eekhout of the VU University Medical Center in Amsterdam, who is the study's lead author.

There are 11 to 20 percent of Iraq war veterans who are afflicted with PTSD symptoms annually, the Department of Veterans Affairs says.

Common symptoms include difficulty in concentrating, extreme sensitivity to all sounds, feelings of fear, nightmares and disorientation.

While short-term effects of PTSD and mental health have been at the center of a number of studies, the timeline of long-term recurrence has received less focus, Eekhout says.

For their study, the researchers looked at data of about 1,000 Dutch military personnel who were deployed in Afghanistan between 2005 and 2008.

They were assessed before their deployment and then a month after their return home.

They were also asked to fill out questionnaires six months later, then a year later, then again two and five years afterward.

The result shows an increase in the level of PTSD symptoms for the first six months after their return, but that dropped back to pre-deployment levels after a year.

However, five years afterward there was a spike in the PTSD levels greater than in any of the previous periods, the researchers say.

Soldiers remaining in the military would likely find that the understanding of their peers and a feeling of safety are helpful in coping with the trauma of their experiences, Eekhout points out.

"However, when over time the connection to a military group diminishes, resilience may wear off as well, contributing to a delayed stress response," she suggests.

The study, appearing in The Lancet Psychiatry, is important because those suffering from PTSD are also prone to depression and anxiety, and often develop substance use disorders, experts point out.

"Therefore it is important to better understand how PTSD symptoms change over time in the context of other mental health symptoms," says Don Richardson, a consultant psychiatrist at the Parkwood Operational Stress Injury Clinic in Ontario, Canada.

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