Peet (2g/d) 2002.

Study characteristics
Methods	Randomised controlled multicentre parallel‐arm trial, 12 weeks
Participants	Participants: 70 participants with a mean age of 44.7 years were recruited by family physicians in the UK who had an interest in depression and experience in conducting clinical trials (split across Peet (1g/d) 2002; Peet (2g/d) 2002; Peet (4g/d) 2002), dates ‐ not reported. Comorbidities: none reported, but possible physical and/or psychiatric comorbidities Adjunctive therapy: Yes in all participants: antidepressants Inclusion criteria: aged 18 ‐ 70 years, score ≥ 15 on the 17‐item HDRS despite ongoing treatment with a standard antidepressant at an adequate dose.
Interventions	Intervention: E‐EPA (2 g/d + 2 g/d placebo), 4 x 500 mg capsules, twice daily Comparator: liquid paraffin (4 g/d), 4 x 500 mg capsules, twice daily Treatment received for 12 weeks
Outcomes	Primary: HDRS (17‐item), MADRS, BDI were all measured at baseline, 4, 8 and 12 weeks; Adverse events Secondary: Response based on HDRS, MADRS and BDI; Trial non‐completion
Notes	Funding: not reported Conflicts of Interest: CoIs declared by one author. Other author works for Laxdale Ltd., UK. Compliance: Capsule counts Depressed mood (continuous): Analysis conducted on HDRS (17‐item) scores at 12 weeks, published ITT data (although 1 participant from the placebo group is missing from these data). Placebo group split across all 3 intervention groups (1 g/d = 5 participants, 2 g/d = 6 participants, 4 g/d = 6 participants), SDs calculated from all other studies also using the HDRS (17‐item) Adverse events: Intervention group: 24 events experienced by 13 participants (8 GI, 2 psychological, 14 other physical), comparator group: 23 events experienced by 10 participants (4 GI, 2 psychological, 17 other physical) Trial non‐completion: Intervention groups (2 per group, reasons not separated by group 1 g/d, 2g/d, 4 g/d) = 6 (3 withdrew consent, 1 lack of efficacy, 1 violated protocol, 1 adverse event), comparator group = 4 (1 withdrew consent, 1 violated protocol, 1 adverse event, 1 lost to follow‐up)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Randomly allocated by PCI clinical services computer" (P. 914)
Allocation concealment (selection bias)	Low risk	"Capsules were packed and coded by PCI clinical services." Participants were randomly allocated on entry to study. "PCI Clinical Services had no involvement with the rest of the trial." (P. 914).
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants took the same number of capsules, placebo and intervention capsules were identical in appearance. Participants, researchers and assessors blind to treatment allocation. (P. 914) It was unclear if they disguised the fishy taste and no assessment to check concealment.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	HDRS/MADRS ‐ assessors blind to treatment allocation (LOW) BDI ‐ participant‐rated (HIGH)
Blinding of outcome assessment (Adverse Events)	High risk	AEs assessed by participants
Incomplete outcome data (attrition bias) All outcomes	High risk	HDRS/MADRS/BDI ‐ Not ITT analysis (only 17 participants used in the analysis of placebo group), plus >10% withdrawals
Incomplete outcome data (Adverse Events)	High risk	All AEs reported, but >10% withdrawals
Selective reporting (reporting bias)	Low risk	All outcomes reported (correspondence from author)
Other bias	Low risk	Study appeared to be free from other sources of bias