Immunometabolic Factors in Atypical Depression

Atypical depression is increasingly recognised as a distinct clinical subtype marked by a constellation of energy-related symptoms such as increased appetite, weight gain, hypersomnia and profound fatigue. Underlying this phenotype is a pattern of low-grade systemic inflammation coupled with metabolic dysregulation. Key immunological mediators include elevated levels of C-reactive protein and pro-inflammatory cytokines such as interleukin-6 and tumour necrosis factor alpha. Concurrently, alterations in lipid metabolism—reflected in shifts in very-low-density and high-density lipoprotein fractions—and perturbations in glucose homeostasis and adipokine signalling are prevalent. Emerging evidence also implicates the gut microbiome in modulating both immune responses and metabolic pathways, suggesting a bidirectional dialogue between microbial communities and host physiology. Together, these immunometabolic disturbances appear to fuel the atypical symptom profile, contribute to poor antidepressant response in some patients and heighten cardiometabolic risk. Recognising and stratifying patients according to immunometabolic signatures holds promise for personalised interventions targeting inflammatory and metabolic pathways and for reducing the broader public health burden of this depression subtype.

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Immunometabolic Factors in Atypical Depression publication trend

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Technical terms

C-reactive protein (CRP): An acute-phase protein produced by the liver that serves as a sensitive marker of systemic inflammation.

Atypical energy-related symptoms (AES): A cluster of depressive manifestations characterised by hyperphagia, weight gain, hypersomnia, fatigue and a sensation of heaviness in the limbs.

Cytokine: A class of small secreted proteins, including interleukins and tumour necrosis factors, that orchestrate immune and inflammatory responses.

Glycoprotein acetyls: Composite biomarkers measurable by nuclear magnetic resonance that reflect chronic inflammation and glycation processes in the blood.

Metabolomic signature: A profile of circulating small molecules—such as lipids, amino acids and lipoproteins—that provides a snapshot of physiological and pathological metabolic states.

References

1. Depression with immuno-metabolic dysregulation: Testing pragmatic criteria to stratify patients. Brain Behavior and Immunity (2024).
2. Metabolomics signatures of depression: the role of symptom profiles. Translational Psychiatry (2023).
3. Microbiome and immuno-metabolic dysregulation in patients with major depressive disorder with atypical clinical presentation. Neuropharmacology (2023).