Jun 13, 2007
In a study of almost 22,000 people aged over 40, those who regularly took the oil were less likely to suffer depression than those who did not.
The study in the Journal of Affective Disorders also suggested the longer one took it, the less depressed one became.
The oil is rich in Omega-3 fatty acids which are linked to various benefits.
Children's brains are said to be boosted by Omega-3s, which have also been claimed to reduce the risk of stroke, heart attack and cancer, although some studies have cast doubt on this.
In this latest claim, scientists said a spoonful of cod liver oil could reduce the risk of depression by as much as 30%.
Depressive symptoms among cod liver oil users was 2.5%, compared to 3.8% in the rest of the population.
The researchers looked at 21,835 people aged between 40-49 and 70-74 across Norway between 1997 and 1999.
When compiling their report, they said they also took into account other factors which could impact upon depression, including age, gender, whether one smoked, drank coffee or alcohol, as well as levels of education and physical activity.
Professor David Kendall said given that fish oil seems to improve cardiovascular health, it may not be that surprising to learn that healthier people are less depressed.
He did not rule out the idea that fish oil could directly impact upon depression, but he did warn that socio-economic factors did not appear to have been taken into account in the study. Richer people, he said, tend to be healthier and have less depression.
In the UK, there is growing momentum behind finding alternative treatments for depression, amid mounting concern that too many people are being given prescription drugs such as Prozac after being diagnosed.
Over 31 million such prescriptions were issued in 2006 - a 6% rise on the previous year.