Anhedonia and Increased Evoked Immune Response

Inflammatory cytokines, cortisol, and anhedonia in patients with treatment-resistant depression after consecutive infusions of low-dose esketamine

Anhedonia, defined as a significant loss of interest or pleasure, is one of the core symptoms of treatment- resistant depression (TRD) and is often associated with poor prognosis. This article primarily investigates the changes in anhedonia symptoms, inflammatory markers, and cortisol levels in TRD patients after low-dose esketamine treatments. A total of sixty patients with TRD were enrolled in the clinical study of esketamine. We primarily assessed the severity of depressive symptoms and anhedonia using the Hamilton Rating Scale for Depression (HAMD) and the Snaith-Hamilton Pleasure Scal(SHAPS), respectively, before esketamine treatment and within 24 h after each treatment. Blood specimens were collected before the first treatment and within 1 h after the sixth treatment, measuring the levels of cortisol, interleukin-6(IL-6), interleukin-4(IL-4), and tumor necrosis factor-alpha(TNF-α) in plasma. We found that after six consecutive infusions of low-dose esketamine, patients' depressive symptoms and anhedonia showed improvement. After six treatments, plasma levels of cortisol, IL-6, and TNF-α decreased in patients with TRD, while the anti-inflammatory cytokine IL-4 increased. Multiple linear regression analysis revealed that baseline cortisol levels were correlated with anhedonia, while inflammatory factors showed no significant correlation. Add-on esketamine appears to be a good choice for the treament of the anhedonia in TRD. It has also shown promising effects on altering inflammatory markers in patients with TRD. Moreover, elevated plasma cortisol levels may serve as a potential biomarker for anhedonia in patients with TRD.

Stress to inflammation and anhedonia: Mechanistic insights from preclinical and clinical models

Anhedonia, as evidenced by impaired pleasurable response to reward, reduced reward motivation, and/or deficits in reward-related learning, is a common feature of depression. Such deficits in reward processing are also an important clinical target as a risk factor for depression onset. Unfortunately, reward-related deficits remain difficult to treat. To address this gap and inform the development of effective prevention and treatment strategies, it is critical to understand the mechanisms that drive impairments in reward function. Stress-induced inflammation is a plausible mechanism of reward deficits. The purpose of this paper is to review evidence for two components of this psychobiological pathway: 1) the effects of stress on reward function; and 2) the effects of inflammation on reward function. Within these two areas, we draw upon preclinical and clinical models, distinguish between acute and chronic effects of stress and inflammation, and address specific domains of reward dysregulation. By addressing these contextual factors, the review reveals a nuanced literature which might be targeted for additional scientific inquiry to inform the development of precise interventions.

Validation of a novel method of ultraviolet-induced cutaneous inflammation and its associations with anhedonia

Affective immunology of the skin is a growing area; however, established protocols for measuring individual differences in cutaneous inflammation are lacking. To address this, we present a preliminary validation of Precision Implementation of Minimal Erythema Dose (PI-MED) testing as a method for measuring cutaneous inflammation. PI-MED is a recently adapted protocol, optimized for reproducibility and individual differences research, that uses ultraviolet (UV) light to evoke cutaneous erythema, or inflammatory skin reddening. PI-MED's novel UV dosage schedule produces standardized erythema responses across different skin pigmentation types and shows strong internal consistency within person and good test-retest reliability across 8-10 weeks. In line with predictions, increased PI-MED erythema was associated with heightened anhedonia, across several measures, beyond influences of non-affective covariates. While future work should further refine the dosage schedule for the lightest and darkest skin types, overall, evidence supports PI-MED as a protocol for inducing and measuring individual differences in cutaneous inflammation. Further, PI-MED-induced erythema can expand psychoneuroimmunology research by offering a complementary assessment for general inflammatory tone. This work adds to a growing body of evidence demonstrating a distinct relationship between inflammation and anhedonia.

Combined serum IL-6, C-reactive protein, and cortisol may distinguish patients with anhedonia in major depressive disorder

Neuroinflammation and anhedonia in major depressive disorder (MDD) are closely connected, though the exact mechanism is unclear. This study aimed to investigate the relationships between cytokines, C-reactive protein (CRP), cortisol, and anhedonia, revealing the potential predictive value in identifying anhedonic MDD. In total, 66 patients with MDD (29 with anhedonia and 37 without anhedonia) and 66 healthy controls (HCs) were included. The severity of depression and anhedonia was evaluated using the Hamilton Rating Scale for Depression-24 (HAMD-24) and Snaith-Hamilton Pleasure Scale (SHAPS), respectively. Serum cytokines were measured using flow cytofluorometric kits, while CRP and cortisol were measured using enzyme-linked immunosorbent assay kits. We found higher serum levels of interleukin-2 (IL-2), IL-6, and cortisol in MDD than in HC where anhedonic MDD was highest. CRP and IL-6 were positively associated with anhedonia, and cortisol levels were related to both anhedonia and depression. A combination of IL-6, CRP, and cortisol had optimal predictive value for distinguishing anhedonic MDD. Anhedonic MDD has unique neuroendocrine-immune characteristics compared with those without anhedonia. The combination of IL-6, CRP, and cortisol might be an early marker to distinguish anhedonic MDD.

Subjective arousal and perceived control clarify heterogeneity in inflammatory and affective outcomes

Only a portion of individuals experiencing chronic stress and associated increases in inflammation go on to develop pathological elevations in mood and anxiety symptoms. Some prevailing models suggest that the outcomes of chronic stress may largely depend on individual differences in perceived control. In the current study, we used this theoretical framework to disambiguate the influence of autonomic arousal and perceived control on inflammatory and psychological outcomes in a large sample of adults from the Midlife in the United States dataset (wave 2; MIDUS-2) (Final N ​= ​1030), and further replicated our approach in a second (MIDUS-Refresher) cohort (Final N ​= ​728). Using k-means clustering we created subgroups systematically differing in subjective arousal (high/low) and perceived control (low/high) and compared these subgroups on inflammatory markers and psychological outcomes. Overall results showed that individuals in the high subjective arousal subgroups had higher levels of IL-6, CRP, and FIB, independent of level of CNTL. However, distinctive, and pathological psychological symptom patterns became more apparent when individuals were characterized by both subjective arousal and perceived control. These findings suggest that subtyping individuals based on subjective arousal and perceived control can help us disentangle pathological versus adaptive mental health outcomes in those with co-occurring inflammation and may help identify those vulnerable to psychopathology in the context of physical or psychological stressor exposure.

From childhood maltreatment to adult inflammation: Evidence for the mediational status of social anxiety and low positive affect

Prior work has established a robust association between childhood maltreatment and systemic inflammatory activation later in life; however, the mechanisms involved in this process remain incompletely understood. The purpose of this investigation was to examine potential mechanistic roles for social anxiety (SA) symptoms and low positive affect (PA) in the path from childhood maltreatment to elevations in circulating interleukin (IL)-6, a common biomarker of inflammatory activation. In addition, building on prior work establishing linkages between mindful awareness and reductions in systemic inflammation, we examined the potential role of trait mindfulness as a moderator of the relationships among childhood maltreatment, SA, low PA, and IL-6. A serial mediation model utilizing a large epidemiologic dataset (final N ​= ​527) supported our central hypothesis that the direct effect of childhood maltreatment on IL-6 was fully serially statistically mediated by SA symptoms and low PA (but not high negative affect). Additionally, results indicated that individuals falling in the upper versus lower quartiles of SA symptoms demonstrated significantly elevated concentrations of IL-6, a finding that has not been previously reported. Trait mindfulness moderated the association between low PA and IL-6, to the exclusion of any paths related to negative affect. Additionally, results indicated that the effect of child maltreatment on IL-6 bypasses SA to indirectly impact IL-6 via negative affect. Overall, we conclude that childhood maltreatment and SA symptoms have a significant influence on IL-6, albeit indirectly via low PA, and the influence of PA on IL-6 may be uniquely susceptible to influence by individual differences in mindfulness.