by Amy Scholten, MPH
In recent years, youve probably heard health experts extolling the potential cardiovascular benefits of eating more omega-3 fatty acidsfats found in fish and certain plant foods. Increasing evidence suggests that omega-3 fatty acids may also be beneficial for the prevention and treatment of certain mental disorders, particularly depression.
Omega-3s: From the Land and the Seas
Omega-3 fatty acids, a type of polyunsaturated fat, are considered good fats. Omega-3 refers to their chemical structure. There are three types of omega-3 fatty acids: docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and alpha-linolenic acid (ALA).
The following foods contain omega-3 fatty acids:
Fatty fish, including:
Plant foods, such as:
Many health experts believe that omega-3 fatty acids may be crucial for brain function and that a deficiency could lead to or exacerbate mental illness in certain people.
Researchers Fish for Evidence
Depression has become increasingly prevalent in Western society. Some researchers believe that this may, in part, be due to major dietary changes that have occurred during the past century, which have resulted in a decreased consumption of omega-3 fatty acids. Several studies suggest that omega-3 fatty acids may be beneficial in the treatment of depression.
A study published in the Journal of Affective Disorders found low levels of omega-3 polyunsaturated fatty acids in the red blood cell (RBC) membranes of depressed patients but not in a well-matched healthy control group. The study also found that increasing severity of depression was related to decreasing RBC membrane levels of omega-3 fatty acids as well as decreasing dietary intake of omega-3 fatty acids.
In an issue of the The Lancet, Dr. Joseph Hibbeln, a researcher at the National Institute on Alcohol Abuse and Alcohol Consumption, reviewed data from nine countries and found a high incidence of depression in countries with low fish consumption. He cautioned that various economic, social, cultural, and other factors could have influenced the results of the study. However, additional studies have found that high blood plasma concentrations of docosahexaenoic acid, an omega-3 fatty acid found in fish, have been linked to increased serotonin turnover and lower incidences of depression and suicide.
In the journal Nutrition Reviews, researchers reviewed a number of studies that suggest that there may be an association between extremely low-fat diets, low cholesterol levels, and an increase in the incidence of depression.
Included in the review was an observation by researchers at the University of Arizona that fat restriction and cholesterol-lowering drugs may change concentrations of polyunsaturated fatty acids in the tissues, including nerve tissue. Fat-restricting diets tend to lead to an increased intake of omega-6 polyunsaturated fatty acids and a relative decrease in the intake of omega-3 fatty acids. For certain people, these changes might increase the risk of depression.
The review included other large-scale studies that demonstrated a clear association between low blood levels of omega-3 fatty acids and an increased risk of depression, violence, and suicide.
The researchers concluded that omega-3 fatty acids are crucial for the proper functioning of the nervous system and that an extremely low-fat diet might lead to negative psychological effects in certain people. They emphasized that dietary advice regarding cholesterol reduction, weight loss, and cancer prevention should stress the importance of an adequate intake of omega-3 fatty acids.
Bipolar disorder, or manic-depressive illness, is a brain disorder that causes extreme swings in mood, energy, and ability to function. The disorder is typically treated with mood stabilizing drugs such as lithium carbonate or valproate. However, these drugs are not always very effective and recurrence rates are high.
A Harvard study, published in the Archives of General Psychiatry, found that omega-3 fatty acids were effective in the treatment of bipolar disorder when taken with a standard mood-stabilizing drug. The four-month, double-blind, placebo-controlled study compared omega-3 fatty acids from fish oil (9.6 grams per day) to a placebo (olive oil) in 30 people with bipolar disorder. The mental state of the participants was measured before and after the treatment, using the Clinical Global Impression Scale, Global Assessment Scale, Young Mania Rating Scale, and the Hamilton Rating Scale for Depression. The results were as follows:
Nine of the 14 people who received omega-3 fatty acids had a significant reduction in symptoms, while only 3 of 16 people who received the placebo showed a reduction in symptoms.
None of the participants taking the fish oil experienced a worsening of symptoms during the study, but nine of the participants taking the placebo experienced a worsening of their symptoms.
While most participants in the study were on mood stabilizers, eight received no concomitant medications. Of those eight, the four participants who received the fish oil completed the study without major episodes of mania or depression while only one of the participants taking the placebo did.
The results look promising for using fish oil, in conjunction with mood stabilizers, in the treatment of bipolar disorder. However, Andrew Stoll, MD, lead researcher and assistant professor of psychiatry at Harvard Medical School, cautions against using fish oil as a first-line, single treatment for bipolar disorder.
Schizophrenia is a serious mental illness often characterized by delusions, hallucinations, emotional blunting, and social withdrawal.
A study published in the journal Lipids found that fish oil, which contains omega-3 fatty acids, helped to reduce the severity of symptoms in a group of 24 patients with schizophrenia. Although none of the patients were clinically deficient in fatty acid intake before supplementation, their symptoms improved after being given 10 grams/day of concentrated fish oil for a six-week period.
In 2003, another study showed that ethyl-eicosapentaenoic acid (E-EPA), a type of omega-3 fatty acid, may be helpful in reducing negative symptoms of schizophrenia when used in addition to the patients regular medications.
However, a 2006 systematic review of six studies (including the above 2003 study) concluded that the overall results are inconsistent. Large, well-designed trials are needed to further investigate the potential benefits of this supplement for treating schizophrenia.
Borderline Personality Disorder
Borderline personality disorder is a mental illness often characterized by intense fear of abandonment, mood swings, impulsive behavior, aggression, and self-injury. A recent study suggests that omega-3 fatty acids may help treat the symptoms of borderline personality disorder.
The study, published in the American Journal of Psychiatry, consisted of 30 women who met the diagnostic criteria for borderline personality disorder based on the Structured Clinical Interview for DSM-IV Axis I disorders and the Revised Diagnostic Interview for Borderlines.
During the 8-week study period, 20 of the 30 subjects received two 500 mg capsules of E-EPA . The remaining 10 participants received a placebo of two capsules daily containing mineral oil.
The researchers assessed levels of depression and aggression in the two groups at the beginning and end of the study. At the end of the study, the researchers found that while depression and aggression levels dropped in the group taking the placebo, they had dropped even more in the group taking the omega-3 fatty acid. The researchers concluded that the omega-3 fatty acid usedE-EPAmay be a safe and effective form of treatment for women with moderately severe borderline personality disorder.
Attention Deficit Hyperactivity Disorder (ADHD)
There is some preliminary evidence to suggest that deficiency of omega-3 fatty acids may be responsible for recent high rates of ADHD diagnosis among children. There was a study in South Australia that tested a combination of omega-3 fish oil and evening primrose oil (an omega-6 oil) on 132 children with ADHD. After the 30-week study ended, almost half of the parents reported that their children's symptoms were improved.
The Future of Omega-3s and Mental Health
Additional research is needed to confirm the benefits of omega-3 fatty acids and mental health. However, some psychiatrists have started recommending that their patients with mood disorders eat foods high in omega-3 fatty acids or take supplements such as fish oil. Unfortunately at least one recent randomized trial and a separate Finnish study attempting to correlate omega-3 intake with depression suggested no relationship between intake (or treatment) and depression.
A Few Caveats
While most people can probably derive health benefits from eating more fish and omega-3 fatty acids, regardless of whether these improve depression, there are a few things to keep in mind:
Never use omega-3 fatty acids as a replacement for your psychiatric medication unless you have your doctors approval.
Fish oil supplements may cause side effects such as indigestion, gas, and fishy-smelling belches; however, this is less apt to be a problem if you start with a low dose and work your way up.
In general, fish oil supplements are safe. However, there is a slight possibility of increased bleeding. Therefore, consult your doctor before taking fish oil supplements, especially if you plan on having surgery.
If you take fish oil supplements, make sure they have been stripped of excess vitamins A and D, which could be toxic if taken in large amounts.
If you are pregnant or nursing, avoid shark, swordfish, king mackerel, tuna, and tilefish since they may be contaminated with mercury or other environmental pollutants.
Even if you are not pregnant, buy products that were checked for contaminants, like mercury or other heavy metals.
American Psychiatric Association
American Dietetic Association
Canadian Council on Food and Nutrition
Mental Health Canada
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Last reviewed October 2007 by Richard Glickman-Simon, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.