A team of researchers at the Erasmus University Medical Centre in Rotterdam, Netherlands, looked at the association between depression and the fatty-acid composition of blood plasma in 264 subjects with depressive symptoms and 461 randomly selected reference subjects who screened negative for depression.*
After an overnight fast, all of the participants had their blood drawn, which was then analyzed for omega-3 and omega-6 fatty acids and for C-reactive protein (an indicator of immune response). The Dutch scientists found a correlation between the intake of fatty acids and depressive disorders in the elderly after adjustment for demographic and biological factors. As the amount of omega-3 fatty acids increased in the participants' diets relative to omega-6 acids, the depression declined.
*Tiemeier H, van Tuijl HR, Hofman A, Kiliaan AJ, Breteler MM. Plasma fatty acid composition and depression are associated in the elderly: the Rotterdam study. Am J Clin Nutr. 2003 Jul;78(1):40-6. (Source: Life Extension Magazine, May 2004.)