For the first time, researchers have found that lung cancer patients who have a combination of high levels of depression and inflammation at diagnosis are later found with continuing depressive symptoms in the next several months, even as they receive new, promising therapies.
The study found that having both maladies at diagnosis predicted higher, continuing levels of depression during the next eight months. Those who had only high levels of depression or only high levels of inflammation, or neither of them, showed no changes in depression over time.
In the analyses, the researchers took into account a wide variety of other factors that could affect the results, including age, race, partner status, education, employment status, lifetime smoking, and any cancer treatments the patients received.
"What this suggests is that there may be an additive effect or perhaps a synergy between inflammation and depression that can lead to worse outcomes with depression," said Barbara L. Andersen, corresponding author of the study and professor of psychology at The Ohio State University.
The results are important because high depression levels have been linked to poorer outcomes in lung cancer patients, suggesting that patients with high inflammation and depression may be at particular risk, Andersen said.
The study was published online recently in the journal Biopsychosocial Science and Medicine.
Andersen and colleagues at Ohio State's College of Medicine and The Ohio State University Comprehensive Cancer Center - Arthur G. James Cancer Hospital and Richard J. Solove Research Institute studied 182 patients who were newly diagnosed with advanced lung cancer (Stage IV). The patients were followed with monthly depression assessments for eight months.
A previous study with the same participants found that depression was linked to higher levels of inflammation in lung cancer patients at diagnosis. This study was designed to see how that combination affected future levels of depression, which had not been studied before, Andersen said.
Participants completed a depression measure. In addition, levels of neutrophils and lymphocytes from patients' blood samples were used to calculate a measure of systemic inflammation, called the Advanced Lung Cancer Inflammation Index (ALI). A previous study by Andersen showed ALI from these patients predicted their survival. That study also found that overall, 35% of the patients had moderate to severe depressive symptoms. That study was the first to show that, among these patients with higher levels of depression, upwards of 70% also had high inflammation.
"We found that this is a particularly alarming combination. None of the three other groups in our study - those with just high inflammation, those with just high depression, or those with neither - had increasing levels of depression over the eight months," Andersen said.
Scientists don't know for sure how inflammation and depression interact to increase depression, she said.
One hypothesis is that inflammation in the body, as seen in this study, can be transmitted to the brain, where it settles into the microglia. During inflammation, the microglia can release harmful substances associated with the development of depression.
These findings are important because of all cancer patients, those with lung cancer are among those with the highest rates of depression, Andersen explained. And the fact that depression is already linked to systemic inflammation suggests the risk is compounded.
"Our findings suggest the need to screen for depression and determine inflammation biomarkers at diagnosis of lung cancer," she said.
"This can help identify vulnerable patients who need psychological therapies to reduce depressive symptoms with a possibility of impacting inflammation as some studies have found."
Co-authors on the study, all from Ohio State, were Kylie Park, Peter Shields, John Myers and Sarah Reisinger.
This research received funding from the Pelotonia Beating Lung Cancer in Ohio (BLCIO) research initiative.
