Eating a lot of fish may help reduce the risk of depression, scientists have said.
Researchers in China analysed 26 studies involving more than 150,000 participants and found higher fish intake was associated with a reduced risk of depression in those conducted in Europe - but not in the other continents studied.
They found a slightly stronger association between high fish consumption and lowered depression risk in men (20%) compared with women at 16%.
The team said the reason for their findings was not entirely clear, but suggested that the omega-3 fatty acids found in fish may alter the microstructure of brain membranes and modify the activity of the neurotransmitters, dopamine and serotonin, both of which are thought to be involved in depression.
They said high-quality protein, vitamins and minerals may have a protective effect on depression, while high fish consumption may also be related to a generally healthier diet and better nutritional status, which could itself contribute to a lower risk of depression.
The study, which is published online in the Journal of Epidemiology & Community Health and was led by the Medical College of Qingdao University, concluded that further research was needed.
"High fish consumption was significantly associated with reduced risk of depression only among studies conducted in Europe, and not in those conducted in North America, South America, Asia and Oceania," the authors said.
"Presumably, differences in fish type, fish preservation and cooking styles, may be an important determinant in the heterogeneity."