Higher CRP associated with loss of libido and increased appetite in young adult Pacific New Zealanders

Background: There is evidence to show that certain subgroups of depressed people also exhibit raised levels of chronic, systemic inflammation. This study tested the hypotheses that associations between inflammation and depression would be more likely for the somatic symptoms of depression and, within this symptom cluster, most likely for those symptoms characteristic of the atypical depression subtype (increased appetite, hypersomnia, and fatigue).Methods: Mixed graphical models were fitted to a community sample of New Zealand born, Pacific young adults (N=239; 40% male; mean age = 19.85 (SD = 0.35) to identify associations between inflammatory markers (C-reactive protein (CRP), Interleukin-6 (IL-6), and Tumour necrosis factor alpha (TNF-a)) with depression subscales and individual depression symptoms, after adjusting for covariates. Results: There was evidence of associations between higher CRP with loss of libido and increased appetite, pre and post covariate adjustment. There were no associations between CRP with appetite disturbance measured as a composite symptom, which conflated increased and decreased appetite, nor with appetite decreases. High body mass index (BMI) was robustly associated with higher CRP and also with loss of pleasure and self-dislike, but not with increased appetite. Conclusions: The results support the hypothesis that the depression-inflammation link is being driven by some somatic depression symptoms, and partially endorse links between inflammation and atypical depression subtype. The findings also provide some evidence for the existence of a depression phenotype, typified by immune and metabolic dysregulation, and increased appetite, and demonstrate the importance of disaggregating symptoms related to appetite into increased and decreased.