An analysis of existing research suggests that eating lots of fish may protect against the development of depression. Pooling data from multiple studies conducted over more than a decade, the scientists found a significant association between consumption of fish and a lower risk of depression, but they do stress that this is only an observational study, so no definitive conclusions on cause and effect can be drawn. It could be that those eating more fish already had healthier diets and lifestyles in general, which could benefit mental health.

There have been many studies looking into whether or not eating fish might curb depression, but the results have been varied. This spurred one group of researchers to conduct a meta-analysis, in which they combined the results of 26 separate studies involving more than 150,000 participents, to see if they could find an overall trend. It indicated that eating fish might cut your risk of developing depression by 17%, but only for European studies. The results are published in the Journal of Epidemiology & Community Health. 

Affecting an estimated 350 million people globally and growing, depression is now the leading cause of disability worldwide, according to the World Health Organization. With the disorder becoming a rising public health issue, there is an increasing interest in identifying lifestyle factors that might be contributing to, or protecting against, its development. With many studies focusing on diet, in particular the possible benefits of eating fish, the researchers of this new study looked at relevant articles published between 2001 and 2014.

They found 16 articles, which included 26 studies, suited to the meta-analysis. Ten of these studies involved following a group of people who did not have depression at the start, and seeing who then goes on to develop it. The rest looked at the association of depression with other variables of interest from a population at one point in time. They found that those eating the most fish had a 17% lower risk of developing depression compared to those who ate the least amount.

Interestingly though, this only applied to those studies conducted in Europe. The researchers suggest that this might be because some of the studies outside of Europe had a smaller number of participants, and so no overall conclusions of any meaning could be drawn.

Because all these studies were observational, and correlation does not mean causation, no definitive link could be established. The researchers note how different studies assessed the nutritional values of the fish in different ways, and that the type of fish and how they were prepared could also have differing effects. They also admit that depression diagnoses between studies were “largely inconsistent.”

Despite this, they do say that more research should be carried out on the potential link, as there may be a plausible biological explanation. This includes the suggestion that omega-3 fatty acids, found in high amounts in fish, might influence the levels of two brain chemicals linked to depression – dopamine and serotonin – and thus impact a person’s mood. The researchers suggest that more work should look into whether the type of fish consumed has any impact on mental health.