Roughly one in five cancer patients struggle with post traumatic stress disorder (PTSD) in the aftermath of diagnosis and treatment.

A recent study from Malaysia indicates that PTSD is a fairly common result of the long and difficult process of living with and treating cancer. Though most commonly associated with soldiers returning from war, PTSD can result from many different forms of trauma. The disorder can sometimes go unnoticed, or be misdiagnosed, causing those suffering to endure psychological distress that can lead to suicide in some situations.

Hidden Pain

Researchers from the National University of Malaysia followed 469 cancer patients starting one month after their diagnosis to four years later. Roughly 20 percent showed some symptoms of PTSD six months after their diagnosis, as researchers detail in a paper published Monday in the journal Cancer. By the fourth year, that percentage had dropped to just over six percent, though a third of those initially diagnosed actually saw their symptoms worsen after four years. It’s a reminder that cancer can have detrimental effects even long after remission, and evidence that counseling services and pharmacological interventions could be warranted for some cancer patients.

PTSD is characterized by frequent flashbacks to a traumatic event, as well as painful and intrusive memories and nightmares. Those suffering from the disorder are often frequently on edge and can experience depression and anxiety as a result of the trauma, as well as be susceptible to violent or emotional outbursts and have trouble connecting with those closest to them.

For cancer patients, this can translate to a hesitation to return for follow-up appointments for fear of bringing up stressful memories, as well as anxiety caused by even minor aches, pains and sicknesses, which spark fears of remission. In addition, some patients may not seek help during the course of their treatment for fear of appearing weak, according to lead author Caryn Mei Hsien Chan.

“Many cancer patients believe they need to adopt a ‘warrior mentality’, and remain positive and optimistic from diagnosis through treatment to stand a better chance of beating their cancer. To these patients, seeking help for the emotional issues they face is akin to admitting weakness,” Chan says in a statement. “There needs to be greater awareness that there is nothing wrong with getting help to manage the emotional upheaval — particularly depression, anxiety, and PTSD — post-cancer.”

Getting Treatment

There are some indications that interventions like cognitive behavioral therapy can help cancer patients deal with the stress of the disease, and various drugs targeting stress hormones may also provide some relief. Indeed, among breast cancer patients, who received special care and therapy at the hospital the study was conducted at, rates of PTSD were over three times lower. That’s promising, though, as a 2016 review study of PTSD care for cancer patients found, much of the hard evidence for the benefits of therapy so far is slim and further study is needed.

Therapeutic benefits could also come from an unlikely place: psychedelics. Two studies published last year looked at how giving psilocybin, the active ingredient in “magic mushrooms” to terminally-ill cancer patients affected their levels of anxiety and depression. Both studies found a significant improvement in the patients’ outlook, and indicated that it helped them come to terms with the disease and with their own mortality. The same effect could hold for those coping with cancer’s lingering pall. Other studies, both of PTSD and depression using psychedelics, have also returned positive results, and anther psychoactive drug, MDMA, just received a “breakthrough therapy” designation from the FDA, clearing the way for further trials.