Loneliness and acute stress reactivity: A systematic review of psychophysiological studies.

Physiological reactivity to acute stress has been proposed as a potential biological mechanism by which loneliness may lead to negative health outcomes such as cardiovascular disease. This review was conducted to investigate the association between loneliness and physiological responses to acute stress. A series of electronic databases were systematically searched (PsycARTICLES, PsycINFO, Medline, CINAHL Plus, EBSCOhost, PubMed, SCOPUS, Web of Science, Science Direct) for relevant studies, published up to October 2016. Eleven studies were included in the review. Overall, the majority of studies reported positive associations between loneliness and acute stress responses, such that higher levels of loneliness were predictive of exaggerated physiological reactions. However, in a few studies, loneliness was also linked with decreased stress responses for particular physiological outcomes, indicating the possible existence of blunted relationships. There was no clear pattern suggesting any sex- or stressor-based differences in these associations. The available evidence supports a link between loneliness and atypical physiological reactivity to acute stress. A key finding of this review was that greater levels of loneliness are associated with exaggerated blood pressure and inflammatory reactivity to acute stress. However, there was some indication that loneliness may also be related to blunted cardiac, cortisol, and immune responses. Overall, this suggests that stress reactivity could be one of the biological mechanisms through which loneliness impacts upon health.