Long chain polyunsaturated fatty acids and depressive illness.

A study of lipids in the plasma and erythrocyte membrane of patients suffering from depressive illness, patients with other psychiatric disorders and women using oral contraceptive agents is reported. It shows that there are differences in the concentrations of long chain polyunsaturated fatty acids (LCP) and linoleic acid (18:2?6) in the plasma choline phosphoglycerides (CPG) and erythrocyte phospholipids of patients suffering from endogenous depression, patients suffering from postpartum depression and women using oestrogen and progestogen combined oral contraceptive agents, compared with those of matched controls. The expected effects of these differences on membrane function and the synthesis of prostaglandins and related compounds are discussed. One of the aims of the study was to ascertain whether measurement of the LCP composition of the plasma CPG would be of value as a diagnostic tool for endogenous depression: although the difference from matched controls is highly significant (p < 0.001), it is concluded to be insufficient to be used as the sole diagnostic criterion. The concentration of docosahexaenoic acid (22:6o3) correlates with the severity of depression in the endogenous group, but not in the reactive group. Total plasma cholesterol is low in the endogenous group compared with controls, but there is no abnormality in the free; esterified ratio. There is no difference in the total plasma CPG, the relative proportions of erythrocyte phospholipids or the ratio of cholesterol: phospholipid in erythrocytes between any of the groups of psychiatric patients and matched controls. The phospholipid LCP concentrations normalise with clinical improvement in the endogenous group, hut are unaltered in the reactive group. Patients receiving prophylactic lithium treatment have similar concentrations of LCP in their plasma CPG to matched controls. Possible reasons for the differences in phospholipid LCP concentrations are investigated and discussed. Finally, some suggestions for future research are made