How Loneliness Gets Under the Skin: Inflammation Mediates the Relationship Between Loneliness and Gait Speed.

OBJECTIVE: Loneliness is linked to interleukin 6 (IL-6), a marker of systemic inflammation, which chronically has deleterious effects on physical and mental health across the adult life span. This study investigated cross-sectional relationships among loneliness, IL-6, demographics, multimorbidity, depression, obesity, friendship quantity, and slowed gait. METHODS: Data from the Midlife Development in the United States Biomarker Project, a national adult sample ( N = 822; age range, 26-78 years) was used for this study. The PROCESS macro tested the hypothesis that IL-6 would mediate the relationship between loneliness and gait, after adjusting for demographic and health risk factors. RESULTS: Age ( ß = 0.292, p < .001), sex ( ß = 0.197, p < .001), body mass index (BMI, ß = 0.374, p < .001), waist-hip ratio ( ß = 0.242, p < .001), and loneliness ( ß = 0.089, p = .025) but not multimorbidity ( ß = 0.043, p = .20), depression history ( ß = 0.022, p = .47), depression symptoms ( ß = 0.036, p = .28), and number of friends ( ß = 0.022, p = .46) contributed to the variance in IL-6. Serial mediation analyses supported the chained effect of loneliness on walking time through BMI and IL-6. Results also showed specific indirect effects of BMI and IL-6 on walking time, suggesting more than one pathway by which loneliness influences health. CONCLUSIONS: These results suggest that loneliness may increase the risk of systemic inflammation, leading to slowed gait and adverse health outcomes. Psychosocial interventions that address loneliness may provide an optimal treatment target for reducing inflammation and preventing declines in health.

The gut microbiome and depression: a review.

BACKGROUND: Recent explorations into the gut microbiome of humans and animals reveal implications in chronic physical and mental health disorders. Relatively little is known regarding the relationship of gut microbiome and depression. In the current review, we reviewed existing scientific data related to the gut microbiome and healthy patients versus patients with depression. Additionally, scientific literature containing the utility of microbiome interventions to improve depression symptoms was reviewed. METHODS: A PubMed and Clinical Key literature search combined the key terms 'gut,' 'microbiome,' 'bacteria,' and 'depression' to identify studies investigating these relationships. RESULTS: 76 relevant articles were identified. Human and animal studies reviewed examined marked alterations in the dominant bacterial phyla in the gut of individuals with depression, the connection between leaky gut and neuroinflammation in depression, brain regulatory centers impacted by changes in the gut microbiome, and the benefits of the addition of a probiotic/prebiotic for gut and mental health. CONCLUSIONS: The current review confirmed the suspected direct communication between the gut microbiome, brain functioning, and depression. Additionally, studies suggest antibiotics disrupt the gut microbiome. There are important implications for psychiatrists in providing opportunities for intervention and enhancement of current treatments for individuals with depression.