Does Loneliness Hurt? Effect of Loneliness on Inflammator Biomarkers, Appetite Hormone Regulation, and Cognitive...

The literature indicates that the prevalence of loneliness is increasing among adolescents. The role of loneliness in cognitive function, appetite hormone regulation, and inflamatory pathways among typically developing adolescents remains unclear.

We enrolled 78 adolescents without psychiatric disorders in our study. All participants underwent measurements of appetite hormone (e.g., insulin, leptin, and ghrelin) and inflammatory marker levels (e.g., C-reactive protein, interleukin [IL]-6, and tumour necrosis factor-α) as well as cognitive function assessments (e.g., the Wisconsin Card Sorting Test and working memory tasks). Loneliness was classified as mild (≤40) or moderate (41-60) based on the participants' total scores on the University of California, Los Angeles (UCLA) Loneliness Scale.

Adolescents with moderate loneliness exhibited higher IL-6 levels (p = .014) than did those with mild loneliness. We identified no significant associations between total UCLA Loneliness Scale scores and appetite hormone levels or cognitive function (all p > .05). Furthermore, cognitive function did not differ between groups (all p > .05). Self-reported depressive and anxiety symptoms were higher in the moderate loneliness group than in the mild loneliness group.

Our findings indicate that loneliness is significantly associated with elevated IL-6 levels among typically developing adolescents. Loneliness may be a clinical marker for systemic inflammation and for subthreshold depression and anxiety in healthy adolescents. Further longitudinal studies are required to investigate the temporal association between loneliness and systemic low-grade inflammation.