Clinical Briefs

With Comments from John La Puma, MD, FACP

Fish Consumption and Depression

August 2001; Volume 4; 95-96

Source: Tanskanen A, et al. Fish consumption, depression, and suicidality in a general population. Arch Gen Psychiatry 2001;58: 512-513.

"A recent double-blind, placebo-controlled trial of 30 patients with bipolar affective disorder demonstrated a significant benefit of omega-3 fatty acid supplements on reducing episodes of severe mania and depression. Omega-3 polyunsaturated fatty acids (PUFAs) are now regarded as a promising but untested treatment as mood stabilizers. Consistent with these observations, several studies of patients with depression have reported depletions of omega-3 PUFAs in plasma or cell membranes. Previously, a cross-national comparison revealed a 50-fold lower annual prevalence of major depression, which was strongly predicted by higher fish consumption. Since fish is the major source of omega-3 fatty acids in the human diet, the frequent consumption of fish could lead to a high intake of omega-3 PUFAs, thus decreasing the risk of depression.

"Data were gathered on fish consumption, depression, and suicidality among a general population in Kuopio, Finland. A random sample of subjects (n = 3,004) aged 25 to 64 years was drawn from the National Population Register. The study questionnaires were mailed in spring 1999, and 1,767 subjects responded (59%). An ethical review board of the Kuopio University approved the study.

"Depression was estimated with the 21-item Beck Depression Inventory (BDI). A person was considered depressed if the BDI score was greater than or equal to 10. One of the BDI items screens the severity of suicidal tendencies. Suicidality was considered to be present if there were any thoughts of harming oneself. Fish consumption was estimated with a food-frequency questionnaire, which has been reported to be comparable with a seven-day food record. A subject was regarded as a frequent fish consumer if fish were consumed twice a week or more often.

"Both the risk of being depressed (odds ratio [OR] 0.63; 95% confidence interval [CI] 0.43-0.94; P = 0.02) and the risk of having suicidal ideation (OR 0.57; 95% CI 0.35-0.95; P = 0.03) were significantly lower among frequent lake-fish consumers compared with more infrequent consumers in a multiple logistic model even after adjustment for sex, age, marital status, education, employment status, work ability, area of living, financial status, general health, smoking, alcohol intake, coffee drinking, and physical activity. These results are also consistent with a study of 265,000 Japanese subjects followed for 17 years, which found a decreased risk of suicide among subjects with daily fish consumption compared with nondaily consumption.

"Consequently, fish oils may alleviate depression and suicidal tendencies. However, large-scale intervention trials are needed before dietary recommendations to increase fish consumption or omega-3 PUFA intake could be applied to depressed patients or people in the general population."

Comment

We know that 13 oz of fish weekly can prevent sudden cardiovascular death. We think it may be the omega-3 fatty acids in cold-water marine fish that convey this benefit. Is it possible that these polyunsaturated fatty acids also have a psychoactive therapeutic effect?

These data for omega-3 fatty acid use are, of course, epidemiological—based on self-administered surveys and validated food-frequency questionnaires completed by 1,767 Finlanders. The data can only be associative, but there are other supportive data in this same population. An editorialist, who reported two years ago a preliminary, double-blind, placebo-controlled trial on the effect of omega-3 fatty acids in bipolar disorder, cites a study of Icelanders in which lack of seasonal mood change was correlated with omega-3 fatty acid intake. Iceland and Finland are on a similar latitude and share a similar diet. Taken together, these data are more than circumstantial, and seem to be pointing in an evidence-based direction.

Recommendation

Though it may be too early to prescribe fish oils for depression and mood disorders, it is not too early to ask your patients to eat more fish and less red meat for reducing the risk of sudden cardiac death and arterial aging. Patients who want to take fish oils for mood disorder ought not to combine them with anticoagulants.