Fish oil is the common name used for a liquid derived from the bodies of several different coldwater ocean fish species, including tuna, salmon, bluefish, mackerel, and sturgeon. This oil contains substances called omega-3 fatty acids, which the body needs to support certain essential aspects of everyday health. According to the results of a number of modern studies, fish oil supplements can potentially help improve the symptoms of serious mental illnesses such as schizophrenia, bipolar disorder, and depression. Use of these supplements may also help lower the risks for the onset of mental illness. Fish Oil Basics In addition to the species listed above, common sources of fish oil include herring, anchovies, sardines, a herring relative called menhaden, seal blubber, whale blubber, and the livers of a species called cod. Some fish oil supplements contain pure oil, while others also contain vitamin E as an anti-spoilage measure. In addition, specific products may contain additional beneficial substances such as B vitamins, vitamin A, vitamins C or D, or the minerals iron or calcium. Fish oil is generally prized for its omega-3 fatty acid content. Each 3.5-ounce portion of a fish oil-producing species contains roughly 1 gram of these acids, the US National Library of Medicine reports. Omega-3 Fatty Acid Basics Scientists also refer to omega-3 fatty acids as essential fatty acids or polyunsaturated fatty acids. The human brain requires a steady supply of these acids in order to maintain aspects of its normal function that include general information processing and the accurate use of memory. Other vital roles for omega-3s include control of a potentially damaging process called inflammation and promotion of normal growth and development in children and teenagers. The two omega-3 fatty acids found in fish oil are docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). A third omega-3, called alpha-linolenic acid or ALA, comes from plant sources, not fish. Evidence for Effectiveness In a study published in 2010 in the American Medical Association\u2019s Archives of General Psychiatry, an international research team gave fish oil supplements to a group of 41 individuals. All of these individuals were classified as \u201cvery high-risk\u201d for the onset of diagnosable schizophrenia, which means they had elevated chances of developing schizophrenia within a year\u2019s time. Another 40 people with the same risks received fish oil placebos instead of real fish oil. After 12 weeks of treatment, the study participants who received fish oil reduced their chances of developing schizophrenia by roughly 22 percent. In another study, published in 2011 in the journal Translational Psychiatry, a team of researchers from the Indiana University School of Medicine used mice to examine the potential benefits of giving the fatty acid DHA to people with bipolar disorder. These researchers concluded that DHA helps prevent the \u201clows\u201d associated with bipolar depression, as well as the \u201chighs\u201d associated with bipolar mania. They also concluded that DHA achieves its beneficial effects by accessing the same areas of the brain that respond to the effects of antipsychotic medications. Findings from several different modern studies indicate that fish oil or separately packaged omega-3 fatty acids can potentially help reduce the effects of major depression, Johns Hopkins Medicine reports. However, there are two important qualifications to these findings. First, fish oil and\/or omega-3s appear to help relieve depression symptoms when used in combination with antidepressant medications, but not when used as a main form of treatment. In addition, fish oil and omega-3 products that contain both DHA and EPA, or EPA alone, produce treatment benefits; however, supplements that only contain DHA apparently don\u2019t produce any benefit. Considerations When people hear about new or \u201calternative\u201d treatments for mental or physical health problems, they sometimes abandon their current treatments and switch over to the newly proposed remedies on the basis of little or no hard evidence. In this context, it\u2019s important to note that not all studies support the effectiveness of fish oil or omega-3 fatty acids as a preventive or active treatment for mental illness. It\u2019s also important to note that researchers need to collect further evidence before they can fully determine whether or how to use fish oil or omega-3s for any specific type of mental illness. No one with a current mental illness diagnosis, or with high risks for mental illness, should take fish oil or omega-3 fatty acids without consulting a doctor for information and advice.