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

• Association of BDNF, IL-6 and other parameters with depression and cognitive function in patients with cancer
• Patients with depression had impairment of short-term memory, not long-term memory
• Low BDNF is associated with cognitive impairment in patients with cancer
• High IL-6 levels were associated with low BDNF levels
• Depression was dependent on high IL-6 levels, but not on BDNF

BackgroundIncreased 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.MethodsSerum 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).ResultsA 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.ConclusionsLow 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.