Chronic Inflammation and Mood Disorders: Mechanisms and Self-Testable Interventions

The inflammation–mood connection is no longer hypothetical

Recent studies shed light on the connection between inflammation and mental health. A 2021 review by Griffith framed chronic inflammation as a shared biological substrate linking cardiometabolic disease and mood disorders, while a 2026 perspective by Akhgari, Chaves, and Joca argued that failure to resolve inflammation—not just its initiation—may drive metabolic mood disorders. Together they move the field from correlation to mechanism.

Glutamate excitotoxicity (Haroon & Miller 2017), leptin-BDNF axis (Hontecilla-Prieto et al. 2025), and stress-hormone-immune priming (Slavich & Sacher 2019) form a mechanistic triad linking peripheral inflammation to central mood circuits.
Sources: https://www.semanticscholar.org/paper/1adbcfa23c65bce21bbe8dfdc7622af3d6ea2142 · https://www.semanticscholar.org/paper/44d495b009068691501dcc6742c42505f969dfff · https://www.semanticscholar.org/paper/1a087ca9a40282a5fae35c46a80aef64112e2de5

How inflammation rewires mood circuits

The mechanistic thread runs through three convergent pathways. First, Haroon and Miller (2017) showed that pro-inflammatory cytokines increase glutamate release and reduce astrocytic clearance in cortico-striatal circuits, creating excitotoxicity that correlates with anhedonia and psychomotor slowing. Second, Hontecilla-Prieto, García-Domínguez, and Berlanga-Gil (2025) identified leptin—an adipokine elevated in obesity—as a molecular bridge: leptin crosses the blood-brain barrier, activates hypothalamic JAK/STAT signaling, and downregulates hippocampal BDNF, linking metabolic inflammation to depressive phenotypes. Third, Slavich and Sacher (2019) extended Social Signal Transduction Theory by showing that stress-induced inflammatory priming interacts with sex-hormone fluctuations, explaining the 2:1 female-to-male prevalence in major depressive disorder.

Omega-3 PUFAs (Zailani et al. 2023) suppress peripheral cytokines; SPMs (Akhgari et al. 2026) actively resolve inflammation; both converge on reducing central glutamate excitotoxicity and restoring BDNF signaling.
Sources: https://www.semanticscholar.org/paper/4a2db3d0417f3228f9b75c97820eda2baa20db97 · https://www.semanticscholar.org/paper/3524c25189cef59eb8230a0f9e8900e87e841f49

Therapeutic avenues emerging from the mechanism

If glutamate dysregulation, leptin resistance, and failed resolution are drivers, interventions should target those nodes. Zailani, Satyanarayanan, and Liao (2023) reviewed omega-3 polyunsaturated fatty acids (PUFAs) in COPD patients with comorbid mood disorders: EPA/DHA supplementation reduced IL-6 and TNF-α while improving HAM-D scores, suggesting peripheral anti-inflammatory action translates to central benefit. Akhgari et al. (2026) highlighted specialized pro-resolving mediators (SPMs)—resolvins, protectins, maresins—as the next frontier: they actively terminate neutrophil infiltration and promote macrophage efferocytosis without immunosuppression.

A 14-day n-of-1 protocol you can run

• Control window (days 1–7): Maintain habitual diet, sleep, and activity. Each morning measure HRV (RMSSD, 60 s supine), record POMS-SF mood score, and log subjective energy (1–10). If accessible, obtain baseline hs-CRP and fasting leptin.
• Intervention window (days 8–14): Add 2 g/day EPA/DHA (1.2 g EPA / 0.8 g DHA) with the largest fat-containing meal. Keep all other variables constant. Continue daily HRV, POMS-SF, and energy logging.
• Null hypothesis: No within-subject change in mean RMSSD, POMS-SF total, or energy score between windows (paired t-test, α = 0.05).
• Exploratory: If hs-CRP and leptin are measured at day 1 and day 14, test for >20 % reduction.

What remains unknown

The evidence suggests omega-3s lower peripheral cytokines and improve mood scores in comorbid populations, but dose-response curves for EPA/DHA ratios in non-COPD adults are undefined. SPMs are mechanistically compelling yet human trial data are sparse; commercial SPM supplements lack standardization. Sex-hormone×inflammation interactions imply menstrual-cycle phase may modulate intervention response—a variable rarely controlled in existing studies. Finally, glutamate-mediated excitotoxicity has been demonstrated in PET/MRS studies, but non-invasive biomarkers for central glutamate flux remain elusive for self-tracking.

References

1. Tia A. Griffith (2021). Chronic Inflammation: A Link Between Cardiometabolic and Mood Disorders?. https://doi.org/10.25904/1912/4134
2. Halliru Zailani, S. K. Satyanarayanan, Wei-Chih Liao (2023). Omega-3 Polyunsaturated Fatty Acids in Managing Comorbid Mood Disorders in Chronic Obstructive Pulmonary Disease (COPD): A Review. Journal of Clinical Medicine. https://doi.org/10.3390/jcm12072653
3. A. Akhgari, Y. Chaves, S. Joca (2026). 269. Resolution of inflammation in metabolic mood disorders. International Journal of Neuropsychopharmacology. https://doi.org/10.1093/ijnp/pyag040.031
4. George M. Slavich, J. Sacher (2019). Stress, sex hormones, inflammation, and major depressive disorder: Extending Social Signal Transduction Theory of Depression to account for sex differences in mood disorders. Psychopharmacology. https://doi.org/10.1007/s00213-019-05326-9
5. Lourdes Hontecilla-Prieto, D. García-Domínguez, Carmen Berlanga-Gil (2025). Leptin a potential link between obesity and depression. Cellular and Molecular Life Sciences. https://doi.org/10.1007/s00018-025-05892-6
6. E. Haroon, Andrew H. Miller (2017). Inflammation Effects on Glutamate as a Pathway to Neuroprogression in Mood Disorders.. Modern trends in pharmacopsychiatry. https://doi.org/10.1159/000470805