Recent studies have suggested that total serum cholesterol was significantly lower in patients of various psychiatric disorders compared to that of healthy individuals. However, others have shown no association or opposite results. Examination of the differences in the composition of polyunsaturated fatty acids may explain the conflicting results. Pekkanen and colleagues found that lower serum cholesterol was associated with lower mortality due to accidents and violence in coastal Western Finland. However, no association was found in Eastern Finland, which is inland; thus, thc consumption of fish may have been protective. In addition, according to the Epidemiological Catchment Area survey, societies consuming large amounts of fish and n-3 fatty acids appear to have lower rates of major depression. 　　More than 65% of the dry weight of the brain is composed of lipids that play important structural and functional roles. Abnormalities in the polyunsaturated fatty acid composition in the brain can alter membrane microstructure, and consequently, affect brain function. Relationships between n-3 polyunsaturated fatty acids (PUFAs) level and several psychiatric disorders, including schizophrenia, mood disorders, and anxiety disorders, have been reported. We cannot be certain at this stage whether abnormality of serum cholesterol is of primary etiological significance, is secondary to the development of psychiatric disorders, or entirely the result of other factors such as diet, smoking or treatment of psychiatric illness. More systemic studies on the effects of PUFAs supplementation in the treatment of psychiatric illness with control of confounding factors are needed to resolve these issues.