Updated

A cancer diagnosis can leave lasting psychological scars akin to those inflicted by war, with the impact in some cases lasting for years, U.S. researchers found in a study.

More than a decade after being told they had the disease, nearly four out of 10 cancer survivors said they were still plagued by symptoms of post-traumatic stress disorder, or PTSD, said lead researcher Sophia Smith from the Duke Cancer Institute in Durham, North Carolina.

Those symptoms included being extra jumpy, having disturbing thoughts about the cancer and its treatment, or feeling emotionally numb toward friends and family.

One in 10 patients also said they avoided thinking about their cancer and one in 20 said they steered clear of situations or activities that reminded them of the disease, a situation that could potentially become a medical problem.

"You worry if the patient is avoiding medical care, you worry they might not be getting follow-ups," Smith told Reuters Health.

"We don't have data to support that, but we worry about it."

The study, published in the Journal of Clinical Oncology, is based on a survey of 566 patients with non-Hodgkin's lymphoma, a relatively common kind of cancer.

Smith's team had surveyed these patients for PTSD symptoms once before, estimating that about one in 12 had full-blown PTSD. The diagnosis involved a trio of symptoms, including avoidance, arousal and flashbacks.

Many more had one or more PTSD symptoms, however. The newest survey also showed they often persist.

Overall, half of the patients had no PTSD symptoms 13 years after their diagnosis. The problems had disappeared in 12 percent, but had remained or worsened in 37 percent.

"This study found that people seemed to have worse PTSD later on," said Bonnie Green, a trauma expert at Georgetown University who pioneered the study of PTSD in breast cancer survivors, but was not linked to the latest study.

"It's just very stressful for people to be told that they have cancer. You can't just assume that they feel bad now, but it will go away."

She stressed that it's only a minority of patients who develop full-blown PTSD, but added that depression is common after a cancer diagnosis.

The new survey shows that low-income people are extra vulnerable to the psychological impact of living with cancer.

"I am particularly concerned about the patients who are poor or have less resources, said Smith, adding that doctors have to be better at recognizing distress in patients.

"Each time they come in you are asking not only if they're having pain, but also if they are having stress."