Omega-3 supplements in the prevention and treatment of youth depression and anxiety symptoms: A scoping review

**Background:** Depression and anxiety are among the most common mental illnesses in young people, with 50% of lifetime cases beginning before age 14 and 75% before age 24. Omega-3 polyunsaturated fatty acids have shown potential for reducing depression and anxiety symptoms in adults, but research in young people aged 14–24 is limited. This scoping review aimed to synthesize evidence on omega-3 supplementation for depression and anxiety in this age group and to assess whether grey literature accurately reflects the scientific evidence.

**Methods:** Four databases (Cochrane CENTRAL, EmBASE from 1947, PsycINFO from 1806, PubMed from 1996) were searched from inception to 4 August 2021. Eligible studies had a mean participant age between 14 and 24 years, administered omega-3 supplements containing DHA and EPA, measured anxiety and/or depression using validated instruments, and contained empirical data. Grey literature sources were also searched using CADTH checklist and Google advanced search. A stakeholder group of 11 individuals (4 young people with lived experience, 3 parents, 4 healthcare professionals) informed research questions and data interpretation. Risk of bias was assessed using the Cochrane Risk of Bias Tool for RCTs. Narrative synthesis was used due to study heterogeneity.

**Key Results:** 17 empirical studies (N=1240 participants) met inclusion criteria, of which 13 were RCTs. All RCTs examined depression, but only 5 measured anxiety. Daily omega-3 dosages ranged from 1000 mg to 6400 mg of combined EPA and DHA, with EPA proportions from 50% to 85.7%. Treatment duration ranged from 3 weeks to 12 months. For depression: only 2 of 13 RCTs found that omega-3 supplementation led to greater reductions in depressive symptoms relative to placebo—one administering 1400 mg/day for 3 weeks as standalone treatment (Ginty 2015: 67% of omega-3 group vs 20% of placebo group reduced to below clinically indicated levels on BDI) and another administering 2400 mg/day for 12 weeks as adjunct to standard antidepressant therapy (Trebatická 2020: significant reduction in CDI scores). A third study in women with PCOS (Jamilian 2018: 1000 mg/day omega-3 + 400 IU vitamin E for 12 weeks) found reduced depressive symptoms on BDI. The remaining 10 RCTs found null effects. For anxiety: 3 of 5 RCTs found reduced anxiety symptoms—Kiecolt-Glaser 2011 (2496 mg/day, 85.7% EPA, 12 weeks) found a 20% reduction in BAI scores compared to placebo in medical students; Jamilian 2018 found reduced depression/anxiety on DASS42; Robinson 2019 (1140 mg omega-3 + tocopherol, 16 weeks) found reduced anxiety on BPRS in participants not taking lorazepam. Two studies found no effect on anxiety. Only 2 of 13 RCTs had low risk of bias across all 5 domains; selective reporting was the largest source of potential bias (69.2% of studies). 12 grey literature sources met inclusion criteria; 83% recommended omega-3 for depression or anxiety, despite the weak evidence. Only 17% of grey literature sources were rated as excellent in accuracy.

**Clinical Implications:** The review found insufficient evidence to support omega-3 supplementation for depression in young people aged 14–24, consistent with a prior meta-analysis in children aged 6–18. Some evidence suggested omega-3 may reduce anxiety symptoms, but no studies were conducted in clinically anxious populations. No clear moderators (dosage, EPA:DHA ratio, treatment duration, participant characteristics) emerged. The mismatch between scientific evidence and publicly available information is concerning, as grey literature overwhelmingly recommended omega-3 despite weak evidence. Clinicians should be cautious about recommending omega-3 for youth depression or anxiety. Future research should include longer treatment durations (minimum 6 months for omega-3 equilibration), systematic investigation of moderators and mechanisms (particularly inflammatory biomarkers), and trials in clinically diagnosed anxiety populations. Policymakers should prioritize improving the accuracy and accessibility of evidence-based online health information.