To investigate whether long-chain omega-3 (n-3) polyunsaturated fatty acids (PUFAs) improve functioning and psychiatric symptoms in young people with borderline personality disorder (BPD) who also meet ultra-high risk criteria for psychosis.

We conducted a post hoc subgroup analysis of a double-blind, randomized controlled trial. Fifteen adolescents with BPD (mean age 16.2 years, [SD 2.1]) were randomized to either 1.2 g/day n-3 PUFAs or placebo. The intervention period was 12 weeks. Study measures included the Positive and Negative Syndrome Scale, the Montgomery-Åsberg Depression Rating Scale, and the Global Assessment of Functioning. Side effects were documented with the Udvalg for Kliniske Undersøgelser. Fatty acids in erythrocytes were analyzed using capillary gas chromatography.

At baseline, erythrocyte n-3 PUFA levels correlated positively with psychosocial functioning and negatively with psychopathology. By the end of the intervention, n-3 PUFAs significantly improved functioning and reduced psychiatric symptoms, compared with placebo. Side effects did not differ between the treatment groups.

Long-chain n-3 PUFAs should be further explored as a viable treatment strategy with minimal associated risk in young people with BPD.