The association between plasma omega-3 fatty acids and suicidal ideation/self-harm in the United Kingdom Biobank

Self-harm is a significant public health concern, with increasing prevalence globally. Omega-3 fatty acids (FAs), particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are known for their health benefits, including potential mental health improvements. This study explores the association between omega-3 FAs and self-harm behaviors using data from the UK Biobank (UKBB).

To investigate the relationship between plasma levels of omega-3 FAs and various measures of self-harm, including passive suicidal ideation and deliberate self-harm, within a large cohort study.

This observational study analyzed data from a random subset of 258,012 participants with plasma omega-3 FA levels, covariate data, and self-harm records. Omega-3 levels were measured using Nuclear Magnetic Resonance (NMR) and are expressed as a percent of total FAs. Self-harm outcomes were assessed through self-reported questionnaires and medical records. Covariates included demographic, health, and lifestyle factors. Statistical analyses involved logistic regression and Cox proportional hazards models, adjusting for relevant covariates. Adjusted odds ratios (aORs) are presented and 95% confidence intervals.

Higher levels of DHA, non-DHA (ALA+EPA+DPA) and total omega-3 were generally inversely associated with passive suicidal ideation, history of self-harm, and future self-harm, with both DHA and non-DHA showing some of the strongest associations. Participants in the highest quintile of non-DHA had a 14% lower risk of passive suicidal ideation in the last year (aOR = 0.86; 95% CI 0.75, 0.99), and the highest DHA levels were associated with a 33% lower odds of history of self-harm (aOR = 0.67; 95% CI 0.55, 0.83). These associations were generally stronger for medical record-based outcomes than for self-reported data.

This study provides evidence that higher omega-3 FA levels, both DHA and non-DHA, are associated with reduced risks of self-harm and suicidal ideation. These findings suggest that omega-3 FAs may play a protective role in mental health, highlighting the potential of dietary interventions to mitigate self-harm behaviors.