LURGAN, Northern Ireland — On a cold February night in 2001, as Joe Holbeach was jogging along the pebbled shores of Newcastle in Northern Ireland, he imagined being taken in by the vicious tide and drowning. Days later, he stood on the edge of the Giant’s Causeway cliff top and gazed down at the steep drop, trying to find the courage to jump.

He didn’t, but like many other survivors of the paramilitary violence during the Troubles in Northern Ireland, he suffers from post-traumatic stress disorder. And to this day he battles the demons that tell him to end his own life.

Twenty years after the Good Friday Agreement ended the Troubles, Northern Ireland has one of the highest suicide rates in the world.

Experts point to numerous factors including poverty, underfunded mental health services and a recent uptick in paramilitary violence. But a leading cause, they say, is PTSD.

Mr. Holbeach, who has received a diagnosis of PTSD, is among the thousands who were caught in the crossfire of Northern Ireland’s guerrilla war, in which bombings, shootings and maimings were enmeshed in daily life for nearly three decades.

“During the Troubles, the suicide rates in Northern Ireland were actually lower than they are now,” Ms. O’Neill said. “It seems that the conflict gave those who may have otherwise been suicidal, a sense of purpose — to fight, to live.”

“But when the Troubles ended,” she added, “many people struggled to make sense of what all that fighting was about and what had been achieved, and then the suicide rates went up.”

The uncertainty over Brexit and the collapse of Northern Ireland’s power-sharing coalition has empowered dissident groups in recent years and threatened the region’s fragile peace. Paramilitary-style punishment shootings and beatings in dissident-run deprived areas — primarily to punish young people for things like petty crimes and drug dealing — rose 60 percent last year, an increase that experts say has contributed to the high suicide rate.

Bernadette O’Rawe, an activist who provides support for the victims of paramilitary shootings in western Belfast, pulled out pictures of some of the worst casualties. A young boy with bloody bullet holes the size of golf balls under his kneecaps, another with a bulging ripped lip. Many of the victims are left crippled.

Of the nine victims the couple helped, three took their own lives. “Suicide is like an epidemic here — there’s about one a week,” Ms. O’Rawe said.