Is Suicide in US Military Personnel Related to Low DHA Status?
Suicide is a global problem that is more prevalent among adolescents, the elderly, war veterans and active-duty military personnel. The latter are of particular concern regarding the Iraq and Afghanistan wars, among whom suicide is the second leading cause of death (13.1%) compared with the ninth rank for the general US adult population (1.8%). Up to 2009, the number of suicides exceeded the number of combat deaths in the US military. Although a past attempted suicide is a strong predictor of suicide, other conditions, such as mental disorders, including depressive symptoms, social and environmental factors increase the risk.
Low concentrations of long-chain (LC) PUFAs or DHA have been associated with various psychiatric disorders, including major depressive disorder, bipolar disorder, violent behaviors and suicide. There is some evidence that supplementation with omega-3 (n-3) LC-PUFAs is associated with reduced suicidal thinking and depressive symptoms in individuals with a history of self-harm. However, a study of the DHA content of the prefrontal cortex of adolescent suicide victims reported that suicides and controls did not differ in their cortex content of DHA, although patients with major depressive disorder had significantly lower levels of DHA in the orbitofrontal cortex compared with individuals without depressive symptoms. A recent study in Japanese men and women who died by suicide found that higher fish or n-3 LC-PUFA intakes were not associated with a lower risk of suicide. The exception occurred in women with very low fish intake (0 to 5th percentile of intake) whose suicide risk was 3.4 times greater than in women with mid-range fish intakes. The relationship between risk of suicide and LC-PUFAs, particularly for DHA, begs clarification.
Cognizant of the high rate of suicide among returning US military personnel, investigators at the Uniformed Services University and the National Institutes of Health, Bethesda, USA, aimed to determine if DHA status in US military personnel was associated with the risk of suicide death. In a case-control design, they randomly selected 800 active-duty US military suicide deaths and matched them with 800 controls, all of whom had serum samples and health data on record. Cases were confirmed by the Armed Forces Institute of Pathology and in records of the Department of Defense Medical Mortality Registry. Controls were selected randomly by the Armed Forces Health Surveillance Center. In addition, health assessment data, mental health and substance abuse records were obtained within 6 months of completion of the last deployment closest to the date of serum sampling.
Descriptive characteristics of the sample donors included age, sex, rank, ethnicity, branch of service and year of sample. Suicides differed from controls in ethnicity and service branch, so these factors were considered in the statistical analysis. Associations between suicide and DHA were determined from Z-scores derived from the fatty acid analyses, which were treated as continuous variables in logistic regression models. DHA levels were divided into various categories, e.g., quartiles, octiles, and adjusted odds ratios for suicide death calculated per 1 standard deviation.
The concentrations of n-3 PUFAs in the suicide samples and controls did not differ significantly for alpha-linolenic acid and EPA, but the odds ratio for suicide death per 1 standard deviation in DHA (percent total serum fatty acids) was statistically significant (14% greater risk of suicide for each standard deviation of lower DHA, OR = 1.14, 95% CI, 1.02 – 1.27, P <0.03). The key risk assessment, however, was the odds ratios of suicide by octiles of serum DHA (Table). Risk of suicide was 62% greater among men with serum DHA below 1.75% compared with those having levels above 1.75% (OR = 1.62, 95% CI 1.12 – 2.34, P < 0.01). EPA and ARA were not associated with suicide risk. Lower levels of stearic acid and dihomo-γ-linoleic acid were also associated with increased risk of suicide. Certain feelings, such as detachment and avoiding situations as well as particular combat experiences (seeing a coalition member killed, discharging one’s weapon) were also significantly related to suicide risk.
Several observations in this study deserve mention. One is the low levels of total n-3 LC-PUFAs and DHA in all participants. According to a recent assessment of risk for fatal ischemic heart disease related to LC-PUFAs, all military participants in this study except for those with total n-3 PUFA levels of 4.5% or more, of which there were only a few, would be considered at risk. With DHA values clustered at the low end of the range, it is more difficult to demonstrate an effect of higher DHA. However, an increased risk of suicide with low EPA and n-3 LC-PUFA status was reported in Chinese individuals hospitalized for attempted suicide. Intervention data are limited to one study in which a 12-week intervention with EPA and DHA in patients with repeated self-harm was associated with improvements in well-being and scores for suicidality.
The context of the study is compelling because of the high rate of military suicide. Although some suicide prevention programs have demonstrated effectiveness, interventions for active-duty service personnel as do exist are insufficient. This observational report cannot address causality, but it may spur thinking and action about appropriate steps to reduce the high risk of suicide in the military. This could have direct application to the civilian population as well. Clearly, more intervention trial data are needed.
Lewis MD, Hibbeln JR, Johnson JE, Lin YH, Hyun DY, Loewke JD. Suicide deaths of active-duty US military and omega-3 fatty-acid status: a case-control comparison. J Clin Psychiatry 2011; Aug 23 online. doi:10.4088/JCP.11m06879. [PubMed]
Manor I, Magen A, Keidar D, Rosen S, Tasker H, Cohen T, Richter Y, Zaaroor-Regev D, Manor Y, Weizman A. The effect of phosphatidylserine containing omega-3 fatty-acids on attention-deficit hyperactivity disorder symptoms in children: A double-blind placebo-controlled trial, followed by an open-label extension. Eur Psychiatry 2011; Epub July 30. [PubMed]
Lespérance F, Frasure-Smith N, St-André E, Turecki G, Lespérance P, Wisniewski SR. The efficacy of omega-3 supplementation for major depression: a randomized controlled trial. J Clin Psychiatry 2011;72:1054-1062. [PubMed]
Jackson PA, Deary ME, Reay JL, Scholey AB, Kennedy DO. No effect of 12 weeks’ supplementation with 1 g DHA-rich or EPA-rich fish oil on cognitive function or mood in healthy young adults aged 18-35 years. Br J Nutr 2011;25:1-12. [PubMed]