Neurocognitive function, brain-derived neurotrophic factor (BDNF) and IL-6 levels in cancer patients with depression

Background: Increased IL-6 and decreased brain-derived neurotrophic factor (BDNF) levels have been implicated in the pathophysiology of depression. The objective was to assess the influence of BDNF and IL-6 on cognitive function and depression in patients with cancer.

Methods: Serum BDNF and plasma IL-6 were measured in patients with metastatic cancer. Diagnosis of depression was established according to DSM-IV criteria. Cognitive function was assessed by the Verbal Learning and Memory Test (VLMT).

Results: A total of 59 patients were recruited in this study. Only IL-6 levels were significantly elevated in patients with clinical depression (35.7 vs. 6.9 pg/ml; p<0.001). There were no differences in hemoglobin levels (p=0.3) or BDNF levels (p=0.16). Patients with clinical depression showed significant impairment of short-term memory (STM) (24.4 vs. 37.5; p=0.01), but not of long-term memory (LTM) (3.9 vs. 2.8; p=0.3). STM was dependent on the level of BDNF and younger age (b=0.60; p=0.001; b= -0.63; p=0.003, respectively). IL-6 was not only strongly associated with depression, but was an independent predictor of BDNF level as well (b= -0.50; p=0.01). LTM was associated only with a good KPS (b=0.47; p=0.037). Hemoglobin levels and the prior number of chemotherapy lines were not predictive of memory performance.

Conclusions: Low BDNF is associated with cognitive impairment, STM, in patients with cancer, however no influence on depression could be found. IL-6 is strongly associated with depression and an independent predictor of BDNF levels.