Saleem said he can still see the faces of the young men he shot.

More than a decade after sniper duty in the Lebanon-Israel war of 2006, he still has nightmares.

“In this region we have a saying that a young man is like a rose,” he said, then breaks off for a moment and does not finish the sentence.

Saleem’s first marriage broke down after the end of the war. His children stayed with him. He admits he was probably hard to live with.

“I never talked about the war. I never talked about it at all. I locked everything away,” he said.

After the war, he drove refuse trucks for a while. Now he is a taxi driver. He has remarried, but he does not speak to his new wife about the war.

“I don’t like to leave the children,” he said. “I don’t like to be outside the house at night. For years and years I didn’t want to talk about it at all, but now I look online at night to try to understand.”

Saleem’s experiences since the war sounds familiar to researchers who deal with post-traumatic stress disorder, but what about his family’s?

There is a growing interest in the idea of transgenerational trauma (TGT) — trauma that is somehow transmitted from parent to child and on down the generations.

Saleem is careful with his children, and probably even over-protective of them, but what about others? He knows men who cannot stop themselves from raging at their children, shouting, lashing out.

“Sometimes the children are the same way,” Saleem said. “They see how their fathers are and they think this is the way to be.”

For Joseph El-Khoury, a Lebanese psychiatrist who works with members of the militias that fought in the conflicts that have shaken Lebanon over the past 50 years, Saleem’s account is no surprise.

The men he deals with are “very angry and resentful, and what they choose, a lot of them, is just to completely withdraw, do the minimum … you’ve learned that by serving or being part of a group you sacrificed yourself, lost friends and you’re not better off,” El-Khoury said.

The resentment, the anger, he said, is being taught to a newer, younger generation.

“They hold the political views and the social views that link to that conflict, but they don’t make that connection,” El-Khoury said.

You can see it in small ways, for example in the geography of the town, or who hangs out where, he said.

“There are no barriers, but there are mental barriers, psychological barriers,” El-Khoury said.

Trauma is what happens in our mind as a result of a particular event or series of events. It will affect different people differently: Some might be fine or suffer only a few consequences, while for others the effects could evolve into post-traumatic stress disorder or depression.

For many years conflict was seen as the main culprit, but increasingly physical and sexual abuse are thought to be triggers too.

“One aspect of suffering one or several traumas is a greater susceptibility to stress,” said Peter Fonagy, a psychoanalyst, clinical psychologist and chief executive of the London-based Anna Freud National Centre for Children and Families.

In 1966, a Montreal-based psychiatrist called Vivian Rakoff said that he was seeing greater numbers of adolescent offspring of Holocaust survivors.

“It is almost as if their parents, in an attempt to justify their survival, demanded qualities of their children which were the accumulation of their expectations of all the dead who were murdered,” he said.