April 9, 2001 -- If an apple a day keeps the doctor away, could a serving of salmon keep the psychiatrist at bay? According to a Finnish study, perhaps.
Researchers in Finland have found that people who eat more fish are less likely to have symptoms of depression. Many fish contain high levels of omega-3 polyunsaturated fatty acids -- one in particular, docosahexaenoic acid, or DHA, is necessary for optimal brain function.
But while the result of this study, written by Antti Tanskanen and colleagues and published in this month's issue of Psychiatric Services, supports findings from previous studies linking low DHA levels with depression, the researchers say their study can't prove a cause-and-effect relationship and that large-scale trials are needed before dietary recommendations to increase fish consumption among psychiatric patients, or even the general population, can be made.
"They are making a connection, but it is hard to say how strong a connection it is," Barbara Rasco, PhD, JD, tells WebMD. Rasco, an associate professor in the department of Food Science and Human Nutrition at Washington State University in Pullman, reviewed the study for WebMD.
The researchers asked more than 3,000 Finnish adults whether they experienced depressive symptoms. They also were asked various questions about their lifestyles, such as marital status, employment status, smoking habits, alcohol and coffee intake, and education level, in addition to how much fish they consumed.
The researchers found that the likelihood of having mild to severe depression was 31% higher among infrequent fish consumers, who ate fish twice a month or less, than in people who ate fish once a week or more. The connection between depressive symptoms and fish consumption was particularly strong among women.
"I wouldn't be surprised that omega-3 fatty acids would play a role in mental health because of their important role in nervous system function and [biological] importance in our diet overall," Rasco says.
"But," she says, "frequent fish consumers tend to have a healthier lifestyle and better diet overall ... a lower-fat diet, reduced caffeine and alcohol intake, less smoking, more physical activity. ... And I think people who tend to have that kind of lifestyle tend to be happier people overall; they feel better, and that tends to make them happier." She notes that the study doesn't do a terrific job of teasing out the effects of fish consumption from the other lifestyle factors.