Reference
Lewis MD, Hibbeln JR, Johnson JE, Lin YH, Hyun DY, Loewke JD. Suicide deaths of active-duty US military and omega-3 status: a case-control study. J Clin Psychiatry. Aug 23, 2011 [Epub ahead of print].
Background
Suicide rates among active US military members have reached an all time high. Since the beginning of Operation Enduring Freedom in Afghanistan and Operation Iraqi Freedom, the suicide rate has doubled, rivaling the death rate on the battlefield. The greatest cause of inpatient bed utilization in the US military is for mood disorders, with major depression and suicide risk being the most prominent.1 The military has been exploring various links to causative factors but has yet to identify a specific causal link to the suicide cases. To date, this is the largest study that explores the potential biological factors associated with suicide deaths.
Design
This study is a retrospective, case-control study that compared measured serum fatty acid composition from 800 randomly selected active duty US military suicide deaths to 800 matched controls (2002–2008.) In this study, serum fatty acid levels were quantified as a percentage of total fatty acids. Prospectively collected serum and subsequent supportive data was made available from the Armed Forces Health Surveillance Center (AFHSC). The AFHSC is a repository that currently contains more than 40 million serum samples with matched health data from US military personal.
Data, specifically a post deployment health assessment, from soldiers was collected at 6 months after their last deployment. Information collected included theater of deployment, exposure to stresses during deployment, self report of mental health status, and indication for referral to mental health services. In addition, mental health, substance abuse, and related ICD-9 diagnosis data was collected.
Participants
Eight hundred suicide deaths were identified among varying branches of the armed services, including the Army, Navy, Air Force, and Marines, from 2002 to 2008. Cases were included only if the official cause of death was ruled a suicide by the Armed Forces Institute of Pathology and Department of Defense Medical Mortality Registry after a detailed investigation. All cases selected had a serum sample that had been collected within 12 months of the suicide. Controls were selected and matched by age, sex, rank, and availability of a serum drawn within the past 12 months.
Key Findings
This study found that low serum docosahexaenoic acid (DHA) status is a significant risk factor for suicide deaths among active-duty US military. When compared to other general populations such as North Americans, Australians, Mediterranean people, and Asians, nearly all US military personal had a lower omega-3 status. The Chinese ranked lower than US military personal, specifically in a population of suicide attempters.
The primary hypothesis that lower omega-3 status, specifically DHA, would be associated with a greater risk of suicide was proven correct. In fact, it was found that with each standard deviation of lower DHA, there was an associated 14% greater risk of suicide. The correlation was so strong that only subjects with the highest levels of DHA appeared to be protected. When compared to the highest octile, the risk of death by suicide was 62% greater for men with lower serum DHA status.
This study clearly demonstrates the impact of nutritional deficiency and the role it may play in mental health status.
Of interest, a history of any visit with a substance abuse diagnosis was not associated with suicide. Women in general had a higher DHA percentage when compared to men; however fewer women were included in the sample.
Practice Implications
An increased risk for suicide is likely mutifactorial and includes social, psychiatric, and environmental risk factors to name a few. For soldiers, and many others who experience post-traumatic stress syndrome, the complexity involved with regard to psychological health can never be underscored; however this study clearly demonstrates the impact of nutritional deficiency and the role it may play in mental health status. Low DHA status can easily be reversed using low-cost dietary intervention strategies that could include simple meal planning or dietary supplementation. For instance, a 4-ounce piece of wild salmon contains approximately 1,300–1,500 mg of omega 3s. A high-quality, molecularly distilled fish oil, high in DHA, is also an option.
The American Psychiatric Association currently recommends consumption of at least 1 gram daily of omega 3s (eicosapentaenoic acid [EPA] plus DHA) for all patients with psychiatric disorders.2 The US Food and Drug Administration has determined that up to 3 grams per day of omega 3s (EPA plus DHA) is generally recognized as safe.3
Study Limitations
A major limitation of this study, because it is retrospective, is the inability to characterize neuropsychiatric symptoms—specifically stress exposure, traumatic brain injury, alcohol use or abuse, and other associated risk factors. Also, because it is case-controlled, there is a potential that the presence of mental illness or substance misuse change dietary habits, which may have affected serum fatty acid levels. However, while serving oversees, a soldier’s diet is somewhat limited to the rations being served, which is a significant component as to the underlying nutritional deficiencies.
It is important to understand that the causal association between higher omega-3 status and prevention for or treating suicidal ideation cannot be inferred from this study alone. However, large, randomized, controlled studies have been done to explore omega 3s (EPA and DHA) in subjects with severe depression.4 Long-term intervention studies exploring primary prevention of suicide attempts using DHA supplementation must be done, specifically within the US military.
