Levels of omega-3 fatty acid in serum phospholipids and depression in patients with lung cancer

Previous studies suggested that omega-3 fatty acids (FAs) have therapeutic effects against depression, but there is no evidence in the oncological setting. Our preliminary study reported the association between lower omega-3 FA intake and occurrence of depression in lung cancer patients. To explore the association further, the present study examined whether depression was associated with lower levels of omega-3 FAs in serum phospholipids. A total of 717 subjects in the Lung Cancer Database Project were divided into three groups by two cutoff points of the Hospital Anxiety and Depression Scale depression subscale (HADS-D). In all, 81 subjects of the nondepression and minor depression groups (HADS-D<5 and 5⩽HADS-D⩽10, respectively) were selected to match with 81 subjects of the major depression group (HADS-D>10) for age, gender, clinical stage, and performance status. Fatty acids were assayed by gas chromatography and compared among the three matched groups. There were no differences between the major depression group and nondepression group in any FAs. The minor depression group had higher mean levels of docosahexaenoic acid (mean±s.d. (%), nondepression: 7.40±1.54; minor depression: 7.90±1.40; major depression: 7.25±1.52, P=0.017). These results suggested that serum FAs are associated with minor, but not major, depression in lung cancer patients.