Zenab Ahel looks at her newborn quadruplets at Ash-Shifa Hospital in Gaza City, three boys and a girl. (Wissam Nassar, Maan Images)

Fifteen-year-old Nour Aidi has hardly spoken in seven years since Israeli soldiers bulldozed the olive trees around his home, barricaded his family in a room and turned the house into a base, fortified with sandbags, camouflage netting, barbed wire and machine guns.

The soldiers stayed 12 months and then moved into barracks next door where, for another four years, they continued to control when Nour and his family could leave and enter the house.

Israel withdrew its army and settlers from Gaza in 2005, but the soldiers still occupy Nour's life. Nour is introverted, angry, sometimes violent, and without friends.

Nearly four miles away, on the other side of Gaza's deadly perimeter, similar behaviour has also taken root.

In the Israeli border town of Sderot Raziel Sasson, 13, sleeps huddled next to his mother and father. Raziel retreated to his parents' bed four years ago after a rocket fired by Palestinian militants in Gaza exploded in a playing field, knocking him from a tree. He eventually returned to his own bed only to later move with the entire family into the lounge downstairs where they have slept for the past year, sheltering from the escalating attacks.

Raziel has watched rockets fired into his front yard and seen explosions cause serious injury. He has nightmares about the rockets and lately he has taken to sleeping in the reinforced steel box that his brother built in the living room for added protection.

Sleeping problems, fears, and fits of aggression are just some of the many symptoms of severe stress affecting the majority of children in Gaza and Sderot.

They live on the frontline of the world's oldest conflict, which in the past eight years has killed 5,848 people, wounded thousands more and traumatised countless families.

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Raziel has spent four years in therapy; Nour has been seeing counsellors for six months.

But Israeli and Palestinian researchers suspect the toll is worse than either the number of deaths or psychological symptoms of this protracted conflict suggest.

Alon Friedman, a biology professor and neurologist at Israel's Ben-Gurion University, who has been studying the effect of stress on the brain for 10 years, is now planning a study of the children of Gaza and Sderot.

Limited research on adults and more extensive testing on animals shows that stressful events, especially life-threatening situations, can cause long-term neurological and biological damage. When stressed the brain secretes powerful hormones such as cortisone which, in big or prolonged doses, can change the brain's structure, resulting in an inability to process intense emotions or form new memories. Such hormones can also induce epileptic seizures and attention deficit and hyperactive disorders.

"The connections between brain cells are very sensitive to stressful stimuli or experiences," Friedman said. "These change the way your brain cells interact and when that happens your thoughts and the way you express them also change."

Hormones such as cortisone can also damage internal organs, including the kidneys, heart and muscles.

The distress of living under military rule in Gaza caused Nour's younger sister to stop eating. Now 12, she has the body of a six-year-old. His mother developed a stomach disorder that activates when she is nervous, and his eldest brother is clinically depressed.

In Sderot Raziel's mother has been diagnosed with diabetes, which the doctor said she developed because she "has no quiet".

If psychological symptoms are any indication, Gaza and Sderot could be in the throes of an emerging epidemiological disaster.

To read the full article please visit The Guardian.