Table 1.
Biomarkers of Inflammation and Stress Accounted for in the Meta-Analyses.
| Biomarker | Description | Beneficial Levels |
|---|---|---|
| Biomarkers of stress | ||
| AA | Alpha amylase; stress-sensitive enzyme; levels change in response to physiological and psychological stress; elevated levels indicate stress [20] | ↓ |
| ACTH | Adrenocorticotropic hormone; stress-sensitive hormone; promotes cortisol production; elevated levels indicate stress [21] | ↓ |
| Cortisol | Stress-sensitive hormone; elevated levels indicate physiological and psychological stress; mediates effects of psychological distress on physiological health [22] | ↓ |
| DHEA-S | Dehydroepiandrosterone sulfate; stress-sensitive hormone; acts as cortisol antagonist; lower levels indicate stress [23] | ↑ |
| Biomarkers of inflammation | ||
| CRP | C-reactive protein; inflammation-sensitive protein; elevated levels indicate inflammation; relevant for physical and mental illnesses [18] | ↓ |
| IL-6 | Interleukin-6; pro-inflammatory cytokine; elevated levels indicate inflammation and are related to worsening health status; promotes sickness behavior; relevant for mental illnesses, e.g., depression [19,24] | ↓ |
| IL-8 | Interleukin-8, pro-inflammatory cytokine; elevated levels indicate inflammation and are related to worsening health status; involved in pathogenesis of mental disorders [25] | ↓ |
| IL-1β | Interleukin-1β; pro-inflammatory cytokine; elevated levels indicate inflammation and are related to worsening health status; relevant for neurodegenerative diseases [26] | ↓ |
| IL-1ra | Interleukin-1ra; inflammatory cytokine; elevated levels indicate inflammation and are related to worsening health status [27] | ↓ |
| IP-10 | Interferon gamma protein 10; inflammatory chemokine; elevated levels indicate inflammation and are related to worsening health status [28] | ↓ |
| NF-κB | Nuclear factor kappa-light-chain-enhancer of activated B cells; pro-inflammatory transcription factor; elevated levels indicate inflammation and are related to worsening health status; possibly concerts psychosocial stress into cellular activation [29] | ↓ |
| TNF-α | Tumor necrosis factor alpha; inflammatory cytokine; elevated levels indicate inflammation and are related to worsening health status; relevant for pathogenesis of mental disorders [19] | ↓ |
| Biomarkers indirectly related to inflammation and stress | ||
| BDNF | Brain-derived neurotrophic factor; relevant for neuronal and synaptic development; reduced levels are related to neurodegenerative diseases [30] | ↑ |
| EGF | Epidermal growth factor; decreased levels seem to be relevant for the pathogenesis of stress-related and mood-related disorders [31] | ↑ |
| FKBP5m | Methylation of immune-related protein; reduced methylation negatively influences the body’s stress response, e.g., in patients with post-traumatic stress disorder [32] | ↑ |
| LTL | Leukocyte telomerase length (LTL); influenced by stress and inflammation; reduced LTL is related to mental illnesses [33] | ↑ |
| NP-Y | Neuropeptide-Y; relevant for stress and anxiety regulation; decreased levels negatively influence the body’s stress response [34] | ↑ |
| SLC6A4 DNAm | Methylation of SLC6A4 gene; responsible for serotonin reuptake from synaptic gap; elevated methylation leads to a faster reuptake; relevant for mood and stress-related disorders [35] | ↓ |
| sOXT | Oxytocin; seems to have anti-stress and anti-inflammatory capacities; increased levels of sOXT reduce inflammation and stress [36] | ↑ |