We included only randomized controlled trials (RCTs) that evaluated the effects of omega-3 fatty acid supplementation in chronic pain conditions. Eligible participants were required to have experienced pain for at least 3 months, and trials had to compare omega-3 supplementation with placebo, usual care, sham product, or an active comparator. Studies were required to report at least one pain-related outcome at any follow-up time point. We excluded non-randomized or quasi-experimental studies, animal studies, abstracts without full data, reviews, editorials, and duplicate publications.

A systematic search was performed in PubMed, Embase, the Cochrane Library, and Web of Science from database inception to February 14, 2025. The search strategy combined terms related to omega-3 fatty acids (“omega-3,” “fish oil,” “EPA,” “DHA,” “polyunsaturated fatty acid,” “Omegaven” etc.), trial filters (“randomized controlled trial,” “clinical trial”), and chronic pain descriptors (“chronic pain,” “persistent pain,” “fibromyalgia,” “headache,” “migraine disorders,” etc.). Equivalent keywords and controlled vocabulary (MeSH in PubMed, Emtree in Embase) were applied as appropriate for each database. No restrictions were imposed on language, publication year, or publication status. The full search strategy is provided in the Supplementary material.

Search results were imported into EndNote X9 (Clarivate Analytics), and duplicates were automatically removed. Two reviewers independently screened titles and abstracts, retrieved potentially eligible full texts, and assessed them against the pre-specified inclusion criteria. Discrepancies were resolved through discussion until consensus was achieved. Reasons for exclusion were documented at the full-text stage. In addition, the reference lists of all included studies, relevant reviews, and prior meta-analyses were manually screened to identify additional eligible citations.

Data extraction was independently performed by two reviewers using a standardized collection form. The extracted information was systematically organized into spreadsheets and categorized according to key study characteristics, including author and year of publication, country of origin, study design, study duration or follow-up period, sample size, participant demographics (e.g., age), type of chronic pain condition, exposure (intervention and control groups), detailed dosing regimen for the intervention, and the instruments used for pain assessment.

All studies reporting outcome data as means, mean differences, and standard deviations were eligible for inclusion in the meta-analysis. These values were either directly extracted from the original publications or derived from the available data when necessary. A random-effects model was applied to generate pooled estimates, accounting for anticipated heterogeneity across studies and enhancing the external validity of the findings. This approach yields more conservative effect size estimates, which are particularly appropriate when between-study variability is expected.

Two reviewers independently evaluated the methodological quality of the included studies using the Cochrane Risk of Bias tool for randomized trials (RoB 2) (12). The assessment covered the following domains: random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, completeness of outcome data, selective reporting, and other potential sources of bias. Discrepancies between reviewers were resolved through consultation with a third investigator. For each domain, the risk of bias was categorized as “low,” “high,” or “unclear.”

We also conducted a series of pre-specified subgroup analyses in addition to the primary meta-analysis examining the association between omega-3 fatty acid supplementation and chronic pain. These stratifications included disease type, type of fatty acid supplementation, pain assessment scale [e.g., Visual Analogue Scale (VAS), McMaster Universities Osteoarthritis Index (WOMAC), other tools], geographic region (e.g., United States vs. other countries), and control type (placebo vs. active comparator), as illustrated in the corresponding forest plots. Further subgroup analyses were performed based on intervention duration, categorizing studies into short-term (<3 months) and long-term (≥3 months) groups, in accordance with previous meta-analytic frameworks (13). We also stratified trials by daily omega-3 fatty acid dosage (≤1.35 g/day vs. >1.35 g/day). This threshold was selected based on prior evidence suggesting a therapeutic range between 1.35 and 2.7 g/day (14). For trials that provided dosages in mg/kg/day, the total daily intake was adjusted based on a standard adult body weight of 70 kg.

The meta-analysis was performed using Review Manager (RevMan, version 5.3; Cochrane Collaboration) and Stata (version 15.1; StataCorp). Standardized mean differences (SMDs) were adopted as the primary effect size metric. For each study, the SMD was weighted by the inverse of its variance, and pooled estimates with corresponding 95% confidence intervals (CIs) were subsequently calculated.

SMDs were selected because they allow aggregation of results derived from different assessment instruments across studies (e.g., various pain scales). SMDs were calculated by standardizing the mean difference between intervention and control groups using the pooled standard deviation. An SMD of zero indicates no difference between groups. In this analysis, a negative SMD favors the intervention (indicating pain reduction), whereas a positive SMD favors the control group. According to Cohen’s thresholds, an SMDs >0.8 reflects a large effect, >0.5 a moderate effect, and <0.2 a small effect (13).

For studies that did not provide complete data, a normal distribution was assumed, and the mean and standard deviation were estimated from the reported median and interquartile range (IQR) (15). When a single study reported outcomes for multiple doses of the same supplement, the corresponding SMDs were first pooled within that study to generate a single effect size for the primary analysis. These dose-specific results were subsequently examined in subgroup analyses. The present study utilized meta-regression analysis to investigate the effect of Omega-3 fatty acid intervention duration (1, 2, 3, and 6 months) on analgesic efficacy. The duration of intervention was treated as a continuous moderator to rigorously assess whether analgesic efficacy showed a significant linear trend with increasing duration of intervention.

Statistical heterogeneity was evaluated using Cochran’s Q test and the I² statistic. Both fixed-effect and random-effects models were generated; however, results from the random-effects model were prioritized when heterogeneity was present. A two-sided p-value < 0.05 was considered statistically significant. Publication bias was assessed through the use of a funnel plot, Egger’s test (16), and Begg’s test (17).

The selection process, along with excluded records and reasons for exclusion, is outlined in Figure 1. The key characteristics of the included studies are presented in Table 1. Among the 99 full-text articles evaluated, 58 were excluded for various reasons, including 4 that were reviews or meta-analyses, 20 that were conference abstracts, 9 that did not involve patients with chronic pain, 7 that did not incorporate n-3 fatty acid intervention, 8 with non-RCT, and 10 that lacked relevant outcome measures. Therefore, 41 randomized controlled trials were retained for the final analysis (18–58).

Among the 41 RCTs, 26 trials (18–20, 22–25, 27–32, 34, 35, 40, 41, 43, 45–48, 51, 53, 54, 58) (63.4%) were classified as low risk of bias, 11 trials (21, 26, 37–39, 42, 44, 50, 52, 56, 57) (26.8%) had some concerns, and four trials (33, 36, 49, 55) (9.8%) were classified as high risk of bias. Refer to the Supplementary material for detailed assessments.

In the domain of bias arising from the randomization process, 37 trials (18–20, 22–25, 27–35, 37–41, 43–58) (90.2%) were classified as low risk, as they clearly described adequate random sequence generation and allocation concealment using computer-based or equivalent methods. The remaining four trials (21, 26, 36, 42) (9.8%) lacked sufficient information to confirm proper randomization procedures and were thus classified as having “some concerns.” Regarding bias due to deviations from intended interventions, the majority of studies complied with the protocol and maintained appropriate blinding. All 41 trials (18–58) (100%) were classified as low risk in this domain. In the domain of bias due to missing outcome data, 33 trials (18–32, 34, 35, 37, 38, 40–43, 45–48, 51, 53, 54, 56–58) (80.5%) had a loss-to-follow-up rate below 5% and used appropriate methods for handling missing data, and were classified as low risk. Four trials (39, 44, 50, 52) (9.8%) had >5% missing data but employed valid imputation strategies or provided transparent explanations, leading to “some concerns.” Another four trials (33, 36, 49, 55) (9.8%) had substantial missing data without adequate justification or handling, and were thus classified as high risk. For bias in the measurement of outcomes, all 41 trials (18–58) (100%) were classified as low risk, as outcome assessments were performed by blinded assessors or used objective validated instruments. In the domain of bias in the selection of the reported result, 32 trials (18–35, 39–43, 45–48, 50, 51, 53, 54, 58) (78.0%) reported prespecified outcomes consistent with protocols or registries, while nine trials (36–38, 44, 49, 52, 55–57) (22.0%) were classified as having “some concerns” due to unclear analytical plans or selective reporting.

The primary analysis sought to evaluate the impact of omega-3 fatty acid supplementation on pain intensity compared to control conditions. A total of 41 randomized controlled trials (18–58) with 3,759 participants demonstrated a significant reduction in chronic pain associated with omega-3 fatty acids (SMD = −0.55; 95% CI: −0.76 to −0.34; p < 0.001; I² = 87%). See Figure 2 and Table 2.

To further investigate the time-dependent effects of omega-3 fatty acid supplementation, an exploratory subgroup analysis was conducted, stratified by intervention duration (1, 2, 3, and 6 months). Certain trials reported pain outcomes at multiple time points, indicating that some studies contributed data to more than one subgroup. These results are intended to illustrate potential trends over time, not to be used for direct comparisons between durations. In nine studies (18, 19, 22, 25, 35, 37, 39, 48, 58) with 1-month outcomes, omega-3 fatty acid supplementation led to a significant reduction in chronic pain (n = 667, SMD = −0.27, 95% CI: −0.48 to −0.05, p = 0.01; I² = 42%). See Figure 3 and Table 2. In 10 studies (18, 20, 25, 35, 39, 41, 46, 47, 49, 58) that reported 2-month outcomes, a similar impact was noted (n = 550, SMD = −0.39, 95% CI: −0.61 to −0.18, p < 0.001; I² = 37%). See Figure 4 and Table 2. In 22 studies (21, 22, 24, 26, 27, 29–32, 34–36, 38, 40, 44, 45, 49–53, 56) with 3-month outcomes, pain scores were also significantly improved (n = 1,562, SMD = −0.51, 95% CI: −0.87 to −0.15, p = 0.005; I² = 91%). See Figure 5 and Table 2. In 14 studies (26, 27, 29, 31, 33, 35, 40, 44, 46, 49, 50, 52, 54, 56) reporting 6-month outcomes, the analgesic effect became more pronounced (n = 1,053, SMD = −0.83, 95% CI: −1.22 to −0.45, p < 0.001; I² = 87%). See Figure 6 and Table 2. The meta-regression results demonstrated a significant positive relationship between follow-up duration and analgesic efficacy. Specifically, for each additional month of intervention, the analgesic effect size increased by a factor of 10.3% [exp(b) = 1.103, 95% CI = (1.008, 1.207), p = 0.033]. This finding indicates that as the duration of omega-3 fatty acid intervention increases, analgesic efficacy improves significantly.

Forest plot depicting the pooled and subgroup effects of omega-3 fatty acid supplementation on chronic pain intensity (random-effects model). See Figure 7.

The distribution of study weights was assessed, and no single study significantly impacted the overall pooled effect. Each study contributed relatively equally, with a weight range of 1%–5%, and no outliers were identified. Sensitivity analysis was performed by omitting one study at a time, and the results remained stable, confirming the robustness of the findings.

Publication bias was assessed using a funnel plot, as shown in Supplementary material, which exhibited slight asymmetry with a leftward skew in the distribution of effect sizes. Egger’s test provided marginal evidence of publication bias (p = 0.052), whereas Begg’s test indicated statistical significance (p = 0.009). A trim-and-fill analysis was conducted using a linear estimator under a random-effects model to further explore this possibility. Six potentially missing studies were imputed on the right side of the funnel plot, based on the trim-and-fill method. After adjustment, the pooled effect size remained statistically significant (adjusted SMD = −0.723), suggesting that the analgesic benefit of omega-3 fatty acids is robust and minimally influenced by small-study effects or selective reporting.

In this comprehensive meta-analysis of 41 randomized controlled trials (N = 3,759), Omega-3 fatty acid supplementation demonstrated a moderate, statistically and clinically significant reduction in chronic pain intensity (random-effects SMD = −0.55). Beneficial effects emerged as early as 1 month (SMD = −0.27) and were maintained at 2 months (SMD = −0.39) and 3 months (SMD = −0.51), with the largest effect at 6 months (SMD = −0.83), indicating a time-dependent, cumulative analgesic response. A clear dose pattern was evident: low-dose regimens (≤1.35 g day⁻¹) yielded a better effect (SMD = −0.60) than higher doses (>1.35 g day⁻¹; SMD = −0.53). Subgroup analyses confirmed robust benefit in RA, migraine and miscellaneous chronic pain conditions, while no significant improvement was detected in OA or mastalgia. Risk-of-bias assessment indicated that 63% of trials were low risk and sensitivity analyses showed that removing any single study did not dramatically alter the pooled estimate; trim-and-fill procedures suggested minimal impact of publication bias.

Recent systematic reviews and meta-analyses have come together to support the therapeutic benefits of omega-3 fatty acids supplementation for specific chronic pain conditions. Goldberg et al. (59), pooling 17 randomized controlled trials, demonstrated that omega-3 fatty acids significantly attenuate patient-reported pain intensity in inflammatory disorders such as RA. Concordantly, a 2025 systematic review reported a robust analgesic effect of omega-3 fatty acids in migraine, reflected by a significant reduction in standardized headache-severity scores (60). These observations closely align with the subgroup findings in this study—RA and migraine—thereby reinforcing the reliability and reproducibility of our results across studies. Mechanistically, the analgesic actions of omega-3 fatty acids stem from their multi-tiered modulation of the inflammatory cascade. First, incorporation of omega-3 fatty acids into membrane phospholipids displaces arachidonic acid, lowering biosynthesis of key pronociceptive eicosanoids such as prostaglandin E₂ and leukotriene B₄ (61). Second, omega-3 fatty acids are enzymatically converted to specialized pro-resolving mediators—for example, resolvins, protectins, and maresins—which engage receptors such as FPR2/ALX and ChemR23 to suppress NF-κB signaling and down-regulate pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) (62). Third, omega-3 fatty acids promote macrophage polarization toward the anti-inflammatory M2 phenotype, thereby accelerating active resolution of inflammation (63). Collectively, these anti-inflammatory and neuro-modulatory mechanisms intercept the pathological continuum from peripheral tissue inflammation to central sensitization (64), providing a compelling molecular rationale for integrating omega-3 fatty acids into contemporary chronic-pain management paradigms.

In the present subgroup analyses, omega-3 fatty acids supplementation did not demonstrate a statistically significant analgesic effect in patients with OA or mastalgia. Several factors may account for this null finding. First, OA is characterized by a relatively low-grade inflammatory profile compared to conditions such as RA (65), thereby potentially limiting the therapeutic scope for omega-3’s anti-inflammatory mechanisms. Second, the pathophysiology of OA-related pain is largely mechanical in origin, driven by cartilage wear, subchondral bone changes, and joint loading, with central sensitization often contributing to chronic symptom persistence (66, 67). These mechanisms may be less responsive to lipid-mediated anti-inflammatory modulation. Third, outcome assessment tools may influence effect detection. Most OA trials employed the WOMAC index, which combines pain, stiffness, and physical function subdomains. The multidimensional nature of WOMAC may dilute changes in pain-specific outcomes, especially when compared to more sensitive, unidimensional measures like the VAS. Taken together, these biological and methodological factors may explain the absence of a statistically significant analgesic effect of omega-3 in OA trials. As for mastalgia, the condition is largely hormonally mediated, primarily influenced by cyclical fluctuations in estrogen and prolactin levels rather than inflammatory pathways (68).

In this meta-analysis, the pooled SMD was −0.55. When back-translated to a 0–100 mm VAS using a standard deviation of 20–25 mm—commonly reported in chronic pain trials—this corresponds to an absolute pain reduction of approximately 11–14 mm. At the 6-month follow-up, an SMD of −0.83 equates to a reduction of roughly 17–21 mm on the VAS. Given that the minimal clinically important difference (MCID) for chronic pain in adults is generally considered to be ~10 mm (69), the effects observed in this analysis exceed the threshold for clinical relevance.

For comparison, the established analgesic dose of oral diclofenac (150 mg/day) yields a pooled effect size of SMD –0.56, corresponding to an approximate 14-mm reduction in VAS pain scores (70). The efficacy of omega-3 fatty acid supplementation (SMD –0.55) appears broadly comparable in magnitude; however, unlike nonsteroidal anti-inflammatory drugs (NSAIDs), omega-3 s are associated with a substantially lower risk of gastrointestinal and cardiovascular toxicities. Importantly, omega-3 fatty acids should not be regarded as equivalent to NSAIDs, which remain the first-line therapy for acute pain. Rather, omega-3 s may be best positioned as a safer adjunct or as a long-term strategy in the management of chronic pain. The analgesic effect demonstrated a clear time-dependent escalation: the SMD improved from −0.27 to −0.51 at 1–3 months and reached −0.83 at 6 months. This temporal pattern aligns with the kinetics of omega-3 fatty acids merging into cell membranes, lowering the n-6: n-3 ratio, and enhancing the synthesis of SPMs such as resolvin D1 and resolvin E1. SPMs directly down-regulate nociceptive ion channels and suppress spinal glial activation, providing a “pro-resolution” form of analgesia distinct from conventional anti-inflammatory drugs (62, 71). Our subgroup analysis yielded consistent results, reinforcing the notion that longer durations of omega-3 supplementation are necessary to achieve clinically meaningful pain relief. This finding is consistent with previous reviews suggesting that prolonged supplementation is necessary to achieve clinically meaningful analgesic effects (72). A greater effect was observed in the low-dose group (≤1.35 g day⁻¹; SMD = −0.60), presumably due to saturation of the plasma omega-3 fatty acids curve and better adherence relative to higher doses; nevertheless, doses >1.35 g day⁻¹ remained efficacious. These findings are consistent with prior evidence suggesting that higher doses may not confer additional benefits for chronic pain relief and could even be less effective in certain contexts (31). Accordingly, dosing can be individualized on the basis of cost-effectiveness and patient tolerability.

The present review surpasses earlier syntheses in several critical respects. First, by pooling 41 randomized controlled trials encompassing 3,759 participants—nearly double the sample size of the largest prior meta-analysis—and spanning migraine, RA, neuropathic pain, and musculoskeletal conditions, we markedly increased both statistical power and external validity. Second, we provide the first systematic evidence that the dose–response relationship is non-linear: daily intakes ≤1.35 g of omega-3 fatty acids produced the greatest analgesic benefit, whereas higher doses yielded diminishing returns, implying a ceiling effect or reduced adherence at large dosages. Third, we delineated the full temporal trajectory of benefit, showing that pain relief emerges within 1 month and accumulates steadily through 6 months—information that refines clinical expectations and guides future trial follow-up schedules. Fourth, the review adhered to PRISMA 2020, was prospectively registered in PROSPERO, employed the RoB 2 tool, and confirmed robustness through sensitivity, leave-one-out, and trim-and-fill analyses, thereby minimizing the risk of selective-reporting bias that troubled earlier work. Finally, comprehensive subgroup analyses revealed that that placebo-controlled trials show better effect sizes than active-control trials, underscoring the importance of comparator choice.

This study has several limitations. First, substantial heterogeneity (I² > 50%) was observed due to pooling trials with differences in pain condition, supplement formulation, dosage regimen, intervention length, and participant characteristics. Despite using random-effects models and subgroup analyses, heterogeneity remained in most comparisons, except for the first- and second-month analyses (moderate heterogeneity) and the breast-pain and migraine subgroups (relatively low heterogeneity). Second, 36.6% of trials had “some concerns” or “high” risk of bias, mainly from attrition, selective reporting, and insufficient details on randomization or allocation concealment, which may compromise internal validity. Third, potential confounders such as concurrent NSAID use and baseline omega-3 status were not consistently reported, precluding adjustment. Finally, sex-specific differences in pain response could not be examined, as most trials did not report stratified results. Future studies should better control for these factors and provide sex-disaggregated data. Nevertheless, sensitivity analyses suggested that our overall conclusions remained robust.