Depression

Q: Tell us about your current research findings on depression. Is depression less common in countries where they consume more omega- 3 fatty acids?

A: In April 1998, I published a paper in Lancet in which I compared the annual prevalence of depression across countries to a measure of their fish intake. I took the data points from a paper, published in the Journal of the American Medical Association by Myrna Weissman, M.D.-an epidemiologist at Yale University who is recognized as the world's expert in psychiatric epidemiology; the quality of the epidemiological data is really the gold standard.

The country with the lowest prevalence of depression was Japan at about 0.12, and the highest was New Zealand at almost 6 percent. The paper describes nearly a 60-fold difference in the prevalence of depression-not double or times five-but a 60-fold difference. Virtually all of the differences across those countries appeared to be predicted by how much fish people were eating.

Q: Has the prevalence of depression changed over the past century?

A: I mentioned the differences in incidence of depression across countries, but another way of testing the hypothesis that depression is related to our dietary intake of omega-3s is to look at differences in depression across time, especially in the past century. Long before I began this work, psychiatrists noted, and described very well, that the prevalence of depression has been on a marked increase in the past century depending on what birth cohort you were born in. You are about 100-fold less likely to be depressed by the age of 35 if you were born before 1914, than becoming depressed by the age of 35 if you were born after 1945.

As I mentioned to you, 100 years ago we were eating much closer to our paleolithic diet, because the world was still a much more rural community. We didn't yet have mass agricultural production of corn and soybeans or hydrogenation. My parents still remember when they were eating only butter, which has few omega-6s, instead of margarine.

Q: Have studies demonstrated how depression is affected by fish consumption?

A: I have, for example, done an epidemiological comparison with postpartum depression, although the study is as yet unpublished. It appears that countries where more fish is consumed have much lower rates of postpartum depression. The finding makes sense, because mothers deplete themselves of omega-3 fatty acids while supplying them to the developing infant, presumably for their neuronal development. During gestation and lactation-it is well known-women can become depleted of omega-3 fatty acids. It can take up to 36 months for women to return to their normal levels, so depleted levels of omega-3 fatty acids may very well be one of the factors contributing to postpartum depression. The prevalence of postpartum depression is also much lower in countries where more fish is consumed.

Q: Can omega-3 supplementation help relieve the depression?

A: At the NIH workshop last September, data was presented from a study done by Dr. Antolin Llorente, Ph.D., at Baylor University, where women were given DHA during pregnancy. The study was originally devised to be a biochemical study; it wasn't really designed to study depression or moods. They did, however, recruit depressed women. The women in the study were basically very healthy, normal, upper-class, well-nourished women. Nonetheless, they found that those women receiving the DHA supplements had better measures of attention and concentration than women receiving placebos.

Q: How much DHA were they given?

A: They were given about 200 mg per day of DHA. It was a double-blind, placebo-controlled study in capsules versus a placebo oil.

Q: We've recently read that there is a link between depression and cardiovascular disease. Are the two connected?

A: My data relating countries and their fish consumption, published in the Lancet, suggest that fish consumption protects against depression and cardiovascular disease.

Second, psychologists have known for a long time that there is a link between either depression and/or hostility and cardiovascular disease. If you have one, you are more likely to have the other.

For many years, people have asked the question: Does depression cause cardiovascular disease, or does cardiovascular disease cause depression? What I put forth as a hypothesis is that depression and cardiovascular disease are both manifestations of a common nutritional deficiency.

Depressed patients have been shown to have higher cardiac risk factors from their diets and are, for example, more likely to die of arrhythmias, excessive platelet clotting, or to have elevated cytokines-an immune reaction. All of these conditions parallel what could happen in people with low levels of omega-3 fatty acids.

Most of the work that I have done, and described to you, has largely been theoretical and hypothesis-building. But since that hypothesis, there are five published studies showing that depressed patients have lower levels of omega-3 fatty acids than do control subjects.

Q: Do studies suggest that increasing consumption of omega-3 fatty acids-through diet or supplementation-could have a positive effect for patients with depression?

A: Yes. Some chemistry data also suggest it, as do data among suicide patients and data on hostility and violence. That aside, it took me a while to really come to this opinion. During a conversation with a person at one of the nutritional journals, the interviewer asked, "What's the harm of a depressed patient taking three grams of omega- 3s per day?" Well, there is no harm that we know of. There's no risk and a possible benefit. In other words, it can't hurt and it might help.

Q: How are omega-3 levels measured?

A: Omega-3 levels are measured by analyzing plasma or red blood cells. The test will indicate what concentrations of omega-3 fatty acids are in your blood.

Q: Is the test expensive?

A: It is about a $100 or $150 lab test.

Q: Is the test widely available?

A: No. It is largely a research test at this point. Johns Hopkins' Kennedy Kreger Institute, for example, can do it reliably. The trouble with getting your plasma drawn right now is that while we can analyze the level, we don't know what level is optimal for depressed patients as yet. If you take what is normal for the United States right now in the latter half of the 20th century, I can't tell you if that level is optimal.