Abstract
Pro-inflammatory cytokines, such as interleukin (IL)-6 and tumor necrosis factor-α (TNF-α), are thought to play a fundamental role in the pathogenesis of depression within a subset of individuals. However, the involvement of IL-1β has not been as consistently linked to depression, possibly owing to difficulties in detecting this cytokine in blood samples or that changes in circulating levels might only be apparent in a subgroup of patients who have experienced early-life adversity. From this perspective, the association between early-life adversity and depressive illness might depend on genetic variants regulating IL-1β activity. Considering the inflammatory-depression link, and that women are twice as likely to experience depression compared to men, the current study (N = 475 university students) examined the moderating role of three independent cytokine single nucleotide polymorphisms (SNPs; IL-1β rs16944, IL-6 rs1800795 SNP, TNF-α rs1800629) in the relationship between early-life adversity and depressive symptoms, and whether these relations differed between males and females. The relation between childhood adversity and depressive symptoms was moderated by the IL-1β SNP, and further varied according to sex. Specifically, among females, higher childhood maltreatment was accompanied by elevated depressive symptoms irrespective of the IL-1β SNP, but among males, this relationship was particularly pronounced for those carrying the GG genotype of the IL-1β SNP. These findings suggest that, in the context of early life adversity, genetic variations of IL-1β functioning are related to depressive symptomatology and this may vary among males and females. The present study also, more broadly, highlights the importance of considering the confluence of experiential factors (e.g., early life adversity) and personal characteristics (e.g., sex and genetics) in understanding depressive disorders, an approach increasingly recognized in developing personalized treatment approaches to this illness.
Highlights
The role of inflammation in the pathogenesis of depression is well-established [1, 2]
Scores on an early trauma inventory scale were positively associated with serum IL-6, tumor necrosis factor-α (TNF-α) and IL-1β levels [13], and depressed individuals with experiences of childhood trauma displayed higher peripheral cytokine levels compared to individuals with major depressive disorder who did not experience childhood trauma [14]
Population stratification effects were found, in which the IL-1β rs16944, tumor necrosis factor (TNF)-α rs1800629, and IL-6 rs1800795 genotype distributions significantly differed according to ethnic groups, χ2(16) = 77.0, p < 0.001, χ2(16) = 39.1, p = 0.001, and χ2(16) = 209.5, p < 0.001, respectively
Summary
The role of inflammation in the pathogenesis of depression is well-established [1, 2]. It was suggested that IL-1β changes may be apparent in a subgroup of patients, including individuals with a history of childhood trauma [10]. Consistent with this perspective, early-life adversity might be centrally involved in the relationship between depression and inflammation by promoting changes to inflammatory signaling [11]. In this regard, females who reported sexual abuse in adolescence displayed higher plasma levels of the pro-inflammatory cytokine IL-6 [12]. Scores on an early trauma inventory scale were positively associated with serum IL-6, TNF-α and IL-1β levels [13], and depressed individuals with experiences of childhood trauma displayed higher peripheral cytokine levels compared to individuals with major depressive disorder who did not experience childhood trauma [14]
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