Loneliness is independently predictive of mortality. Thurston and Kubzansky (2009) showed that loneliness was prospectively linked with incident coronary heart disease (CHD) over a 19-year follow- up period, after controlling for standard risk factors in women. Loneliness can increase blood pressure, peripheral resistance, decrease cardiac output and lower heart rate variability.It causes greater blood pressure responses to social evaluative threat and delayed post-stress recovery. Lonely students and adults have higher cortisol levels. Loneliness is associated with an over-expression of genes with elements for the pro- inflammatory agents and an impaired expression of anti-inflammatory response genes.It also reduce natural killer cell activity.
Hackett and colleagues at University College London, investigated the relationship of loneliness with inflammatory responses to standardized mental stress, assessing interleukin-6 (IL-6) , interleukin-1 receptor antagonist (IL-1Ra) , and the chemokine monocyte chemotactic protein-1 (MCP-1). Elevated levels of these are associated with coronary disease.
543 men and women age 53—76 years took part in stress testing, of whom 524 provided data on loneliness and at least one of the key biological measures. Mental stress was induced in the laboratory using two 5-min behavioural tasks.
IL-6 increased in both men and women following stress. The increase was larger in women than men and also emerged sooner.There was no significant change across trials in IL1-Ra . However, men had higher mean levels of IL1-Ra throughout . The concentration of MCP-1 rose following stress in both men and women . Values returned to baseline during the recovery period in men, but remained significantly elevated in women.
Greater loneliness was associated with larger IL-6 and IL-1Ra responses to psychological stress and greater MCP-1 levels in women, independently of age, grade of employment, BMI and smoking status. But no associations were observed in men.
So this study indicates that loneliness is associated with heightened inflammatory response.
Why women? Are social relationships more important for women? . Taylor et al. (2000) have argued that females employ a ‘‘tend-and-befriend’’ response to stress, prioritizing the creation and maintenance of social relationships in managing adversity. This pattern may make women more sensitive to the effects of loneliness, potentially accounting for the heightened inflammatory stress responses observed in lonely women, despite there being no difference in loneliness scores between men and women.
The study was cross-sectional in nature so it is not possible to infer causality.
This is the summary of the article:
Hackett RA, Hamer M, Endrighi R, Brydon L, Steptoe A. Psychoneuroendocrinology. 2012 Nov;37(11):1801-9.