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Cancer patients may often experience post-traumatic stress disorder (PTSD) in the months after their tumors are diagnosed, and mental health issues can sometimes linger for years, a Malaysian study suggests.

Six months after diagnosis, 22 percent of cancer patients reported symptoms of PTSD in clinical evaluations, researchers report online November 20 in Cancer. After four years, about 6 percent of patients had PTSD.

Although overall rates of PTSD decreased over time, one-third of patients initially diagnosed with the mental health disorder had persistent or worsening symptoms four years later.

"PTSD can affect anyone who has witnessed or experienced a serious threat of violence or death," said lead study author Caryn Mei Hsien Chan of the National University of Malaysia in Kuala Lumpur.

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"While PTSD is more often associated with traumatic events such as violent physical and sexual attacks, serious accidents and natural disasters, this includes being diagnosed with cancer, the experience of undergoing cancer treatment and surviving cancer," Chan said by email. "Even if they do not have full-blown PTSD most cancer patients experience some symptoms of it."

For the study, researchers followed 469 patients at one cancer center in Malaysia who had psychological evaluations at various points after their diagnosis. A total of 210 patients died during the four-year study.

Six months after their cancer diagnosis, 27 of 203 patients, or 13.3 percent, met the full criteria for newly developed PTSD, and another 17 people, or 8.4 percent, had several symptoms of PTSD.

Taken together, these two groups show more than one in five patients with serious PTSD symptoms at six months.

At the four-year mark, 10 of 245 patients, or 4.1 percent, had full PTSD and another 5 patients had several serious symptoms. Combined, this translates into serious PTSD symptoms affecting about 6 percent of patients.

Among the 27 people with PTSD after six months, 6 had full-blown PTSD after four years and another 2 had serious symptoms.

Results for breast cancer patients in the study suggest that counseling may help avert or ease the severity of PTSD.

At six months, compared with other cancer patients, people with breast cancer were more than three times less likely to have developed PTSD. In this early postoperative period, breast cancer patients were most likely receiving counseling to help them cope with their diagnosis and treatment.

There wasn't a meaningful difference between breast cancer patients and people with other types of malignancies after four years however.

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The study wasn't a controlled experiment designed to prove whether or how cancer diagnosis or treatment might influence the odds of developing PTSD.

And, not all anxiety related to cancer is PTSD, said senior study author Dr. Fremonta Meyer, a psychiatrist at Dana-Farber Cancer Institute and Brigham and Women's Hospital in Boston.

"Anxiety and fear about recurrence or progression are nearly universal among cancer patients," Meyer said by email. "But intrusive memories and repeatedly mentally replaying difficult aspects of the cancer diagnosis or treatment may be warning signs of PTSD."

While it's encouraging that most patients in the study with PTSD six months after diagnosis no longer had it after four years, doctors and patients should still be aware that its symptoms might last that long for some people, said Dr. Alexander Kutikov of Fox Chase Cancer Center in Philadelphia.

"Studies such as this underscore that involvement of a mental health professional who can appropriately evaluate and help manage psychological and psychiatric responses to a cancer diagnosis is an important part of multidisciplinary cancer care," Kutikov, who wasn't involved in the study, said by email.

Being sad for one year after a cancer diagnosis is normal, but people who aren't getting better at that point may need to see a mental health specialist, said Geertruida H. de Bock, a researcher at the University Medical Center Groningen in the Netherlands who wasn't involved in the study.

"Cancer related post traumatic stress can occur anytime during or after treatment," de Bock said by email. "It's comparable to the death of a close friend or relative."