BACKGROUND:
Clinical trials suggest that omega-3 fatty acids improve the outcome of depression. This study aimed to evaluate the association between intake of cod liver oil, rich in omega-3 fatty acids, and high levels of symptoms of depression and anxiety in the general population.

METHODS:
We used data from the "The Hordaland Health Study '97-'99" (HUSK), a population based cross-sectional health survey from Norway including 21,835 subjects aged 40-49 and 70-74 years. Symptoms of depression and anxiety were measured by The Hospital Anxiety and Depression Scale (HADS). We used logistic regression to study associations.

RESULTS:
Among the participants, 8.9% used cod liver oil daily. A total of 3.6% had high levels of depressive symptoms. The prevalence of such depressive symptoms among the subjects who used cod liver oil daily was 2.5%, as compared to 3.8% in the rest of the population.

The users of cod liver oil were significantly less likely to have depressive symptoms than non-users after adjusting for multiple possible confounding factors (odds ratio=0.71, 95% confidence interval 0.52 to 0.97). These factors included age, gender, smoking habits, coffee consumption, alcohol consumption, physical activity, and education.

In addition, we found that the prevalence of high levels of depressive symptoms decreased with increasing duration (0-12 months) of cod liver oil use (multivariate adjusted test for trend, P=0.04). We were only able to study this latter association in a subset of the population aged 40-46 years.

LIMITATIONS:
Data are cross sectional.

CONCLUSIONS:
The findings indicate that regular use of cod liver oil is negatively associated with high levels of depressive symptoms in the general population.