For many of these patients -- particularly those with severe symptoms -- depression occurs in a toxic blend of high levels of anxiety, traumatic stress, impaired day-to-day functioning and significant pain and other physical symptoms, findings showed.
The results suggest doctors need to screen lung cancer patients for depression and then act to refer patients for care, said Barbara Andersen, lead author of the study and professor of psychology at The Ohio State University.
"Some oncologists may have a mindset that 'of course, you're depressed, you have lung cancer.' This may show an under-appreciation of the breadth of depressive symptoms and other difficulties which accompany it," Andersen said.
Patients with moderate or severe depressive symptoms are more likely to have lower quality of life and worse disease outcomes compared to those also diagnosed with lung cancer but with mild or no depressive symptoms.
"This is more than having a 'low mood.' When severe, the depression rarely gets better without treatment," she said.
The study, published online in the journal Lung Cancer
, also included Ohio State psychology students and researchers from Ohio State's Comprehensive Cancer Center - Arthur G. James Cancer Hospital and Richard J. Solove Research Institute.
Data came from 186 patients at one cancer hospital who had been recently diagnosed with advanced-stage non-small cell lung cancer, which accounts for 85 percent of all lung cancer cases.
Patients completed a telephone survey measuring psychological and physical symptoms, stress and day-to-day functioning.
Results showed that 8 percent of the patients scored at the severe depressive symptom level and 28 percent had moderate depressive symptoms.
Nearly all (93 percent) of the patients with severe depression said the depressive symptoms made it difficult to do their work, take care of things at home and get along with other people.
They reported high levels of hopelessness, and one-third of those with severe depressive symptoms reported thoughts of suicide. They had extreme levels of cancer-related stress, and the least confidence that their cancer treatment would help.
Compared to other cancer patients, those with high levels of depressive symptoms were much more likely to report severe physical symptoms, including 73 percent who said they experienced "quite a bit" or "very much" pain.
Every one of the patients with severe depressive symptoms said they had severe or moderate issues functioning with their usual activities such as work, study, housework and family or leisure activities.
"Depression is just part of what these patients are dealing with. It comes with this whole package of worse functioning, more physical symptoms, stress, anxiety and more," Andersen said.
"All of these can have negative effects on treatment, overall health, quality of life and disease progression."
In general, those with moderate depressive symptoms saw negative effects that were somewhat less -- but still significant -- than those with severe symptoms, the study found.
But there were two striking differences between the groups.
One was in the severity of generalized anxiety disorder (or GAD) symptoms, the most common anxiety disorder. About 11 percent of those with moderate depressive symptoms had moderate to severe GAD, compared to 73 percent of patients with severe depressive symptoms.
"GAD worry or fear can be particularly toxic for lung cancer patients. It can impede decision-making and participation in treatment. Moreover, a common symptom of lung cancer, shortness of breath, can worsen with anxiety and even induce panic for some," Andersen said.
Second, many fewer of the patients with moderate depressive symptoms had impairments in self care (8 percent versus 33 percent in those with severe depressive symptoms), mobility (33 percent versus 73 percent) and usual activities (38 percent versus 100 percent).
Andersen said she was also struck by the "extraordinarily" high levels of cancer-specific stress reported by those with severe depressive symptoms. The levels exceeded the cutoff for likely diagnosis of post-traumatic stress disorder. Andersen said she could not find any other studies of cancer patients with stress levels as high as those for the patients with severe depressive symptoms.
Patients in this study are being followed to provide longitudinal data on their psychological responses and outcomes, including survival.
Andersen said she expects links will be found between depressive symptoms and survival. In previous research, she and her colleagues have found that depression was linked to lower survival rates in breast cancer patients -- but that mental health treatment helped them.
"We need depression to be taken more seriously in lung cancer patients. Because the patients in this research were screened as part of study participation, their physicians were notified of their need for further evaluation and treatment," she said.
"New therapies, targeted and immunotherapy, are significantly improving outcomes. Patients are living longer, and we need to make similar efforts and advancements to treat symptoms such as these and help patients maintain their quality of life going forward," she said.