International studies suggest a correlation between the consumtion of seafood and the level of depression in a population. There is also evidence pointing to the positive effect of omega-3 fatty acids in relation to post-partum depression in women.
One of the first reports to correlate the incidence of depression with the consumption of fish was from a multi-country review led by Joseph Hibbeln at the US National Institutes of Health in Maryland. The incidence of major depression per 100 people was recorded from nine countries together with the average consumption of fish.
Typically, a high incidence of depression occurred in those countries with a low consumption of fish. For example, in New Zealand, with fish consumption around 18kg per annum, depression was scored at 5.8%. In Japan, with a fish consumption of 68kg per annum, depression was 0.12%. Since then further evidence has been gathered. A survey of 3,204 residents of Kuopio in Finland revealed that frequent consumers of fish (twice or more a week) were significantly less likely to suffer from depression and suicidal tendencies than those who ate fish less often or not at all.
A study of 247 healthy adults in Greece found that mildly depressed individuals had 35% lower levels of DHA in their adipose tissues (tissues that store fat) than participants who had no depressive symptoms.
In a Taiwanese study over two months, a daily dosage of 4.4g EPA and 2.2g DHA alleviated depression in patients for whom antidepressants were not working.
Depression is a significant problem with women just after giving birth; the baby blues. Because of the emerging body of information showing that DHA in particular is important for the development of the child’s brain, the possibility that a depletion of DHA in the mother may be associated with the depression has been widely investigated. In 2002 Joseph Hibbeln reported on a study of 14,541 pregnancies in published results from 23 countries. Both lower DHA content in mothers’ milk and lower seafood consumption were associated with higher rates of postpartum depression.
Investigators in the Netherlands reported in 2003 that the levels of available DHA were measured in 112 women at the time of delivery and 32 weeks later. The levels were significantly lower in those mothers assessed to be “possibly depressed” than in the non-depressed group. The authors suggested, “increasing dietary DHA during pregnancy and post-partum seems prudent”.