This is a protocol for a Cochrane Review (intervention). The objectives are as follows:

Main Objective:

This review aims to determine the impact of omega-3 PUFA supplementation versus a comparator (e.g. placebo, wait-list control) on clinician-diagnosed depression or self-reported depression symptoms in children and adolescents aged 6 to 19 years.

Secondary objectives are:

• Estimate the size of the effect of omega-3 PUFAs on depression;

• Estimate the effect of each type of omega-3 PUFA (EPA or DHA), compared with placebo, on depression;

• Determine if the effect is modified by dosage, format (capsule or liquid), sex or age.