Eight family members of the 61-year-old farmer from Svay Rieng province – unnamed to maintain her anonymity – were abducted and killed by the Khmer Rouge in the late 1970s.

But the death that engenders the most bitterness, that has carved out a pervasive feeling of emptiness, and that is impossible to stow away in the past, is that of her mother.

“She felt yearning and longing; this system distresses her daily life,” reads a recap of an interview with the woman, conducted as part of a study on a little-known psychiatric condition called prolonged grief disorder.

The result, published in the Journal of Affective Disorders in August, shows that 30 years after the fact, Cambodians grieving for loved ones killed during the Khmer Rouge era are at risk of developing what has been called a pathological inability to recover, adjust, accept and, ultimately, let go.

The condition, referred to as PGD, was described as a prolonged grieving period of at least six months that is triggered by loss and characterised by intense longing for the deceased person.

In 2008 and 2009, researchers interviewed 775 survivors of the Khmer Rouge, whose policies lead to the death of almost two million people. Slightly more than 14 per cent of respondents exhibited symptoms of the disorder.

Everyone who took part in the study had lost at least one family member between 1975 amd 1979, when the Khmer Rouge held power.

Participants were asked to remember, and analyse, extremely personal events.

“First, we asked them to count the number of family members they lost . . .  just let them count,” study co-ordinator Taing Sopheap, of the Transcultural Psychosocial Organisation, a Phnom Penh-based, non-profit mental health group, said.

“And then we asked them, ‘Among these numbers, who was the deceased person who affected you the most?’ ”

Most answers to that question cited spouses and children. Because the Khmer Rouge rarely buried victims properly, some respondents claim to hear the voices of the unsettled dead, a spiritual belief that complicates moving on from the past.

Factors such as female gender, lack of education, cultural beliefs and number of family members lost were associated with the disorder, but the study’s authors cautioned that these did not constitute a significant risk.

The psychological effects of genocide on Cambodians have, in the past couple of years, gained more attention. As a report earlier this year from New York-based Fordham Law School’s Leitner Centre for International Law and Justice noted: “The starting point for any discussion of mental health in Cambodia is the traumatic impact of the Khmer Rouge period.”

In the regime’s obsession with wiping out the professional classes, lawyers, writers, doctors and judges were killed. The mental-health sector, in its early stages at the time, was obliterated, and the regime ran roughshod over people with even the slightest mental deficiencies.

“During the Khmer Rouge time, there was no in between. People were [deemed] normal or crazy,” said Youk Chhang, executive director of the Documentation Centre of Cambodia.

Researchers have found significant incidences of post-traumatic stress syndrome among survivors. The condition has many things in common with PGD, but is brought on by a wider variety of factors, from experiencing atrocities to the hardship of life in a refugee camp.

PGD fastens solely on the psychological toll that bereavement takes.

Although the study indicates that a low number of the population are at risk, Sopheap, who oversaw the interviews, believes the figure is higher, because of the stigma attached to mental illness.

“Many of them just don’t want to express that they have a psychological problem or a psychosocial problem, because they don’t want their neighbour to stare at their family member.”

To contact the reporter on this story: Joe Freeman at [email protected]