A review of the role of essential fatty acids in brain membrane function and in the etiology of mental disorders, investigating the hypothesis that the ratio between omega-3 and omega-6 fatty acids can be modified by an individual’s food intake (Haag, 2003). The study combined the results of an extensive Medline article search; a survey of biochemistry textbooks currently in print; and an examination of the three-dimensional structure of fatty acids. This research approach gives an overview of the present state of knowledge on the influences of these substances on brain chemistry and functioning and is consistent with other studies on the subject of essential fatty acids and mental health (Chalon, Vancassel, Zimmer, Guilloteau, & Durand, 2001; Hallahan & Garland, 2005; Stoll, Severus, Freeman, Rueter, Zboyan, & Diamond, 1999b).