This is a 12-week-long, randomised, double-blind, placebo-controlled trial exploring the efficacy of a high-EPA multinutrient supplement in the management of sub-clinical anxiety and depression. The investigators focus on young and healthy, adult university students, who may otherwise not be eligible for pharmacological or cognitive behavioural therapy interventions.

First-line treatment for anxiety disorders comprises Cognitive Behavioural Therapy, which is ineffective in a considerable minority of individuals, and pharmacological treatments, which often confer significant side effects. On the other hand, fish-oil-based supplements have been shown to be safer, efficacious alternatives, especially for individuals not eligible for behavioural or pharmacological therapies. Evidence from randomised controlled trials (RCTs) suggests that the long-chain omega-3 polyunsaturated fatty acids (LCn-3 PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may exert beneficial anxiolytic effects. It is also suggested that dietary components such as vitamins and minerals e.g. a-tocopherol (vitamin E) and Magnesium (Mg), may also play a role in mood. It is furthermore theorised that minor allelic carriage of desaturase and apolipoprotein E (APOE) polymorphisms may also influence the putative anxiolytic potential of dietary components. However, despite the abundance of findings in RCTs and animal studies, the putative synergism, additive effects and precise mechanism of action of these macro- and micronutrients on anxiety in humans are largely unknown. Furthermore, the evidence suggests that in depressive states, glutamate homeostasis is dysregulated in frontal brain regions, and in bipolar patients, glutamate concentration is increased in the anterior cingulate cortex. Supplementation with EPA-rich regimes for 12 weeks confers beneficial changes in glutamate concentrations and improvement in functional connectivity between brain regions associated with mood and improvement in global symptoms.

The investigators have designed a randomised, double-blind, placebo-controlled trial to explore the above. Students from the University of Roehampton, aged 18-29 years (Emerging Adulthood), are randomised on a 1:1 allocation ratio, in two groups, for 12 weeks:

1. Active treatment group to be supplemented with a high-EPA multinutrient supplement providing a daily dose of 1,125 mg EPA, 441 mg DHA, 330 mg magnesium and 7.5 mg α-tocopherol.
2. Placebo group to be supplemented with an inert oil mix providing a daily dose of 3,060 mg sunflower seed oil, 60 mg lecithin, 300 mg glyceryl monostearate and 465 mg fish-oil (18%/12% EPA/DHA respectively) for blinding.

Brain hemodynamic and neurochemical changes in response to supplementation with the EPA-rich regime are explored in a subgroup of volunteers by magnetic resonance imaging (MRI). Analyses take place at the Combined Universities Brain Imaging Centre (CUBIC), Royal Holloway, University of London and comprise:

1. Proton Magnetic resonance spectroscopy (MRS), to assess changes in glutamate concentrations in the right and left ventrolateral prefrontal cortex and the anterior cingulate cortex.
2. Functional MRI (fMRI) to assess changes in seed-to-voxel functional connectivity using bilateral orbitofrontal cortex (OFC) and amygdala (AMY) seeds; regions in the brain implicated in the control of emotion and mood.

The choice of the population was made on the basis of its high-risk nature; university students in Emerging Adulthood (18-29 years of age) experience persistent levels of high-academic stress, social disconnection and sleep disruption which increase anxiety levels and exacerbate psychological distress and disengagement from study. University students are thus a high-risk, vulnerable group characterised by higher and increasing rates of anxiety disorders compared to the general population. Furthermore, this population is largely neglected by the therapeutic literature.

The study hypothesis is that:

• Generally healthy, non-clinically anxious university students in Emerging Adulthood experiencing sub-clinical levels of anxiety, will benefit from supplementation with a high-EPA multinutrient supplement, in that the latter will exert beneficial anxiolytic effects.
• Mg and vitamin E will exert additive anxiolytic effects.
• Interindividual variations in fatty acid desaturases (FADS) and APOE genotypes will influence the putative anxiolytic potential of the high-EPA multinutrient supplement under investigation.
• Prefrontal and anterior cingulate cortex glutamate concentrations, and functional connectivity between OFC and AMY, will improve in response to supplementation.

The investigators will perform mixed-model analysis of covariance for the study primary and secondary endpoints, on an intention-to-treat (ITT) and per-protocol (PP) basis. The investigation which will take place at the Department of Life Sciences of the University of Roehampton and the Combined Universities Brain Imaging Centre (CUBIC), Royal Holloway, University of London, harmonised with local and national guidelines and risk assessments, the code of Good Clinical Practice and the Declaration of Helsinki. The study findings will be reported in accordance with the CONSORT statement.

Inclusion Criteria:

• Age 18-29 years
• GAD-7 Score ≥ 5
• PHQ-8 Score ≥ 4
• English language fluency.
• Overall good health.

Exclusion Criteria:

• Self reported BMI ≥ 30 kg/m^2.
• Current tobacco smoker.
• Diagnosis of anxiety, depression/major depressive disorder episode, psychosis, schizophrenia, bipolar disorder, eating disorders, haemophilia, or life-threatening disease during the preceding six months from the beginning of the trial.
• Use of antidepressant drugs during the preceding six months from the beginning of the trial.
• Participation to psychological and/or behavioural interventions during the preceding six months from the beginning of the trial.
• Inability to ingest pills.
• Pregnancy.
• Breastfeeding.
• Known allergy or intolerance to LCn-3 PUFAs, seafood and any of the constituents of the supplement under investigation.
• High intake (more than twice per week) of oily fish (e.g. herring, pilchards, salmon, swordfish, sardines, sprats, trout or mackerel).
• Use of fish oil supplements during the preceding six months from the beginning of the trial.
• Inability to participate in the study for 12 consecutive weeks.

Data will be:

• Fully anonymised
• Stored for 8 years as per University of Roehampton's Research Ethics Committee guidelines and Code of Practice.
• Appended to the final published report as supplemental material.
• Available from the corresponding author upon request.
• Handled, processed, stored and destroyed as per Data Protection Act (2018).
• Collected in Microsoft Excel worksheets in one file per type of experiment including original and normalised values; images/graphs will be stored as .tiff or .jpg files.
• Held encrypted on password-protected, university-owned drives.
• Accessible only by the investigators.
• Submitted for publication within one year.
• Deposited in a public preprint server (e.g. bioRxiv). Additional files with legends explaining how the data has been saved and described will be prepared to allow replicability.

All anonymised data volumes are expected to be small. Long-term backup/archiving will utilise secure in-house facilities and cloud-based storage.

The data will become available upon publication of the study report and will remain available for eight years in accordance with the University of Roehampton's Research Ethics Code of Practice.

Fully anonymised data will be available from the corresponding author upon request.