Why Depression Makes Chemotherapy Less Effective in Cancer Patients

Cancer patients experiencing mild depression survived 200 days longer than their severely depressed counterparts.

Dec 22 2016, 2:00pm

Image: Republic of Mexico/Flickr

A new study has found that cancer patients suffering from depression have decreased amounts of a type of brain protein in their blood, which makes them less responsive to chemotherapy drugs as well as less responsive to their side effects.

The new study, which was presented at the European Society for Medical Oncology's meeting in Singapore last week, is based on the self-reported moods of 186 recently diagnosed cancer patients the day before their treatment began and biometric data following the treatment.

The researchers found that the patients whose cancer had spread to other organs were the most depressed leading up to their chemotherapy treatments, and that this significantly limited their ability to tolerate chemo. The patients with the worse depression experienced vomiting, white blood cell reduction, and longer stays in the hospital and ultimately reduced the length of time that they lived with the disease without it getting worse. Those only considered mildly depressed lived for an average of 491 days, compared with the average 292 days in the severe depression group.

By comparing biometric data collected over the course of a patient's chemotherapy treatments with the self-reported level of depression, the researchers found that those patients suffering severe depression had significantly lower levels of brain-derived neurotrophic factor (BDNF)—a type of protein involved in nervous system formation during embryonic development—in their blood.

While the role of BDNF in regulating depression has been well documented, this study was the first to link its prevalence in the body to the effectiveness of cancer treatments.

"We are the first in the world to report that BDNF can affect chemosensitivity," Yufeng Wu, the head of oncology at the Affiliated Cancer Hospital of Zhengzhou University, told Motherboard. "We examined other factors in patients, but only BDNF was associated with depression."

As found by Wu and his colleagues, higher levels of BDNF in the blood resulted in higher numbers of tumor cells killed by chemotherapy, so patients suffering from depression (which limits BDNF expression) were less responsive to chemotherapy treatments. According to Wu, this suggests that cancer should be thought of as a psychosomatic illness, insofar as the mental state of the patient can affect the trajectory of the disease.

"Psychological treatment should be regarded as equally important to chemotherapy," Wu said.

According to Wu, BDNF levels are non-hereditary and current research suggests its expression is affected by extreme mental stress, as would be experienced by a cancer patient. Indeed, a number of studies have shown that around one-third of cancer patients experience at least mild depression.

According to Wu, the next step is to figure out whether drugs such as fluoxetine, also known as Prozac, can be used to both boost the mood of cancer patients as well as the levels of BDNF in their blood.