Brief reportAssociations between cod liver oil use and symptoms of depression: The Hordaland Health Study
Introduction
Depression is a common disorder with complex etiology. At any time, it affects 2% to 6% of the population in the United States (Kessler et al., 2005) and has a major impact on public health. Hence, identifying risk modifying factors for depression is an issue of high importance.
Biological marker studies have indicated that people with depression have deficits in omega-3 fatty acids (Parker et al., 2006). A few previous studies have suggested that frequent consumption of fish may reduce the risk of depression (Hibbeln, 1998, Tanskanen and Hibbeln, 2001) while others have not found this (Hakkarainen et al., 2004). The possible protective effect might be related to the omega-3 fatty acids content in fish (Smith, 1991, Hibbeln, 1998, Maes and Smith, 1998) and clinical evidence from short-term trials supports the notion that omega-3 supplementation in addition to standard pharmacological treatment improves the outcome for depression (Stoll and Severus, 1999, Nemets and Stahl, 2002, Peet and Horrobin, 2002, Su and Huang, 2003), but others have not found this (Silvers et al., 2005). This may be due to a variation in the dosage of omega-3 administered or to the content of docosahexaenoic acid (DHA) versus eicosapentaenoic acid (EPA) in the omega-3 oil which were used (Sontrop and Campbell, 2006). Cod liver oil is rich in omega-3 fatty acids and, to our knowledge, no studies have so far explored the association between regular use of cod liver oil and symptoms of depression in a community sample.
The aim of the present study was to investigate the association between the use of cod liver oil and depressive symptoms in a general population. Since anxiety is closely related to depression, anxiety symptoms were also studied.
Section snippets
Study population and questionnaire
The Hordaland Health Study ‘97–'99 (HUSK) is a cross-sectional health survey that was conducted from 1997 to 1999 and included all individuals in Hordaland County in Norway born between 1953 and 1957 (29,400 subjects). In addition, the study included 4849 subjects born between 1950 and 1951 and 4338 subjects born between 1925 and 1927, who had participated in an earlier study in the same area from 1992 to 1993 (The Hordaland Homocysteine Study). Of 25,634 recruited participants (66.4% of
Prevalence
The population characteristics in relation to cod liver oil use are given in Table 1. A total of 1947 subjects (8.9%) used cod liver oil daily, and 147 subjects reported that they had taken cod liver oil yesterday, but without daily use. These subjects were included in the reference group.
Association between use of cod liver oil and depression
Daily cod liver oil users were less likely to have high levels of symptoms of depression or high levels of symptoms of combined depression and anxiety, as compared to non-users (Table 2). The association
Discussion
In this large population based cross-sectional study we found that daily use of cod liver oil was negatively associated with high levels of depressive symptoms and that the prevalence of such depressive symptoms decreased with the duration of cod liver oil use after adjusting for multiple covariates. Excluding users of lithium or antidepressants did not change the association between cod liver oil use and high levels of symptoms of depression.
The large sample size and the use of a general
Acknowledgments
The data collection was conducted as part of HUSK (The Hordaland Health Study ‘97–'99) in collaboration with the Norwegian National Health Screening Service. We thank Dr. Alv A. Dahl, M.D., Ph.D., University of Oslo, Norway, for allowing us to use The Hospital Anxiety and Depression Scale (HADS) data collected in The Hordaland Health Study. The present study has been supported by research grants from Helse Vest RHF, the Research Council of Norway (“Senter for grunnleggende sykdomsmekanismer”)
References (15)
- et al.
The validity of The Hospital Anxiety and Depression Scale. An updated literature review
J. Psychosom. Res.
(2002) Fish consumption and major depression
Lancet
(1998)- et al.
Randomised double-blind placebo-controlled trial of fish oil in the treatment of depression
Prostaglandins Leukot. Essent. Fat. Acids
(2005) The macrophage theory of depression
Med. Hypotheses
(1991)- et al.
Omega-3 polyunsaturated fatty acids and depression: a review of the evidence and a methodological critique
Prev. Med.
(2006) - et al.
Omega-3 fatty acids in major depressive disorder. A preliminary double-blind, placebo-controlled trial
Eur. Neuropsychopharmacol.
(2003) - et al.
Is low dietary intake of omega-3 fatty acids associated with depression?
Am. J. Psychiatry
(2004)