A new study found that post-traumatic stress disorder (PSTD) existed more than 3,000 years ago and was first observed with warriors in ancient Iraq around 1300 BC, much earlier than previously thought.

PSTD is a condition of persistent mental and emotional stress brought by injury or a terrifying event. Some of the symptoms observed include disturbed sleep, flashbacks, nightmares, and severe anxiety. According to the PSTD Foundation of America, one in 3 returning troops are being diagnosed with severe PSTD in modern times. Unfortunately, only 40 percent seek help.

Researchers at Anglia Ruskin University studied the translations from ancient Iraq or Mesopotamia. Some warriors claimed that they were haunted by "ghosts they faced in battle," but when the team focused on the symptoms, it turned out that those warriors actually suffered from post-traumatic stress disorder (PTSD).

"The sorts of symptoms after battle were very clearly what we would call now post-traumatic stress symptoms," Prof Jamie Hacker Hughes, a former consultant clinical psychologist for the Ministry of Defence and study author, told BBC News.

"They described hearing and seeing ghosts talking to them, who would be the ghosts of people they'd killed in battle – and that's exactly the experience of modern-day soldiers who've been involved in close hand-to-hand combat."

Prior to the new study, experts believed PSTD started during the time of the Greek historian Herodotus who wrote about the warrior Epizelus during the battle of Marathon in 490BC. Epizelus showed symptoms of PSTD – "suddenly lost sight of both eyes though nothing had touched him."

Prof Hughes provided evidence that PSTD dates to the Assyrian Dynasty in Mesopotamia between 1300BC and 609BC. During that time, males left their families for three years to join the war, went back home and stayed for a year, then repeated the cycle.

"This paper, and the research on which it is based demonstrates that post traumatic psychological symptoms from battle were evident in ancient Mesopotamia... Well before the Greek and Roman eras, before the time of Abraham and the biblical Kings, David and Solomon, and contemporarily with the time of the Pharaohs," Prof Hughes told The Telegraph.

The paper detailing the findings is titled Nothing New Under the Sun: Post-Traumatic Stress Disorders in the Ancient World.