Cytokines and mood in healthy young adults

Abstract

Purpose: A link between chronic inflammation and neuropsychiatric disorders has been demonstrated previously. For example, pro- and anti-inflammatory cytokines have shown to impact neurocircuits relevant to mood regulation. Elevated levels of inflammatory cytokines have been associated with the development of depressive symptoms and elucidating the mechanism by which cytokines influence behavior has received a considerable amount of attention over the past years. Since the immune system appears to contribute to the development of neuropsychiatric disease, further understanding of the link between cytokines and mood alterations could possibly provide insight in the mechanism underlying the evolvement of psychiatric disorders. [1]. The purpose of this study was to investigate the potential relationship between saliva cytokine levels and mood in healthy young adults. Method: The study was conducted among university students at Utrecht University, the Netherlands. Mood states were assessed using a Dutch version of the Profile of Mood States (POMS) scale [2]. The POMS is a psychological rating scale used to assess transient, distinct mood states. The Dutch version of the POMS consists of 32 items, using a Likert type scale ranging from 0 (not at all) to 4 (extremely). Outcome variables include five subscales (i.e., Depression-Dejection, Anger-Hostility, Vigor-Activity, Fatigue-Inertia and Tension-Anxiety) and a total disturbance score (Total POMS Score). Saliva was collected to determine cytokine concentrations. Cytokine levels (i.e. GM-CSF, IFN-γ, TNF-α, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-8 and IL-10) were measured in saliva using Multiplex Bead Immuno-essays (Invitrogen by Life Technologies, California, USA) according to manufacturer's instructions. POMS scores were associated with cytokine levels using nonparametric Spearman correlations. Results: A total of N= 36 healthy subjects completed the study (38.9% men). Mean (SD) age was 21.1 (1.8) years of age. Significant correlations were found between Total POMS Score and IFN-γ (r = 0.485, p = 0.003) and IL-2 (r = 0.485, p = 0.034). Scores on the subscale Anger-Hostility were significantly correlated with GCSF (r = 0.466, p = 0.004), IL-4 (r = 0.364, p = 0.029) and IL-5 (r = 0.395, p = 0.017). Fatigue-Inertia on the other hand was significantly correlated with IFN-γ (r = 0.554, p = 0.001) and IL-2 (r = 0.485, p = 0.003). For Tension-Anxiety, significant correlations were observed with IFN-γ (r = 0.529, p = 0.001), IL-2 (r = 0.332, p = 0.048), GM-CSF (r = 0.371, p = 0.026) and IL-5 (r = 0.376, p = 0.024). No correlation was found between cytokine levels and Depression-Dejection and Vigor-Activity. Also, no significant correlation was observed between TNF-α, IL-1β, IL-6, IL-8 and IL-10 levels and the mood states. Conclusion: This study confirms previous findings that the immune system has an influence on mood states and distress. A significant association was observed between inflammatory cytokine concentrations and Tension-Anxiety, Anger-Hostility, Fatigue-Inertia and Total POMS Score. The strongest relationship was found between the proinflammatory cytokine IFN-γ and mood states.