[The role of omega-3 polyunsaturated fatty acids in mental health]

According to the Ministry of Health, Labour and Welfare, the treatment rate (hospitalization + outpatient) for mood disorders (including bipolar disorder) has doubled over the past quarter-century, from 48 per 100,000 population in 1996 to 94 in 2020. The impact of the COVID-19 pandemic has also contributed to an increase in the prevalence of depression and depressive symptoms across OECD member countries. In Japan, the prevalence rate was 7.9% in 2013, but it has risen to 17.3% in 2020. While the main treatments for depression have traditionally included pharmacotherapy, psychotherapy, and electroconvulsive therapy, there has been a growing body of evidence over the past decade suggesting that improvements in daily lifestyle habits such as sleep, diet, and exercise can contribute to prevention or symptom alleviation. Furthermore, there have been numerous reports highlighting the association between depression and nutrition, particularly with regard to omega-3 polyunsaturated fatty acids. Omega-3 initially gained attention in the 1970s through observational studies conducted in Greenland, focusing on its preventive and therapeutic effects on atherosclerosis. Observational and intervention studies targeting mental health, including depression, have been conducted since around 2000, gradually revealing their mechanisms through animal experiments and other research. In this article, we will present our findings and provide an overview of overseas observational and intervention studies in this field, along with their mechanisms.