US authorities have recommended 'black-box' warnings for antidepressants because of the increased risk of suicidality for individuals up to age 25. There is thus a clinical and ethical imperative to provide effective treatment for youth depression with an acceptable risk-benefit balance. Long-chain omega-3 polyunsaturated fatty acids (PUFAs) play an important role in a range of physiological processes in living organisms. Supplementation with omega-3 PUFAs has been shown to have a range of beneficial effects on both physical and mental health, and results of previous trials suggest that omega-3 PUFAs may be a safe and effective treatment for depression. However, conclusions from these trials have been limited by their relatively small sample sizes.

This trial will test the effectiveness of a 12-week parallel group, double-blind, randomized, placebo-controlled trial of 1.4 g day-1 omega-3 PUFAs in help seeking 15- to 25-year-olds (N = 400) presenting with major depressive disorder. The primary hypothesis is that young people will show greater improvement of depressive symptoms after 12 weeks of treatment with omega-3 PUFAs plus cognitive behavioural case management compared with treatment with placebo plus cognitive behavioural case management.

Because of using a large sample, results from this study will provide the strongest evidence to date to inform the use of omega-3 PUFAs as first-line therapy in young people presenting with major depressive disorder. The study also heralds an important step towards indicated prevention of persistent depression, which may reduce the burden, stigmatization, disability and economic consequences of this disorder.