Reciprocal affiliation among adolescent rats during a mild group stressor predicts mammary tumors and lifespan.
OBJECTIVE
Although the detrimental physical health effects of social isolation have been known for three decades, the answers to how and why social relationships generally improve health remain elusive. Social relationships are not always beneficial, and we examined a structural dimension that may bring about their salubrious effects: affiliative reciprocity during a stressor.


METHODS
In a lifespan study, female rats lived with their sisters and were tested for temperament, affiliative reciprocity during an everyday stressor at puberty, corticosterone response to a stressor, mammary tumor development and diagnosis, and death.


RESULTS
Rats that affiliated more reciprocally during a mild group stressor survived longer (p = .0005), having exhibited a lower corticosterone peak in response to an acute novel stressor in late adulthood (p = .0015), and longer time to the development of spontaneous mammary tumors (p = .02). These effects could not be explained solely by the number of affiliative interactions or individual temperament. Indeed, affiliative reciprocity and neophobia were independent and predicted mortality additively (p = .0002).


CONCLUSIONS
Affiliative reciprocity during a stressor, a structural quality of social interactions, protected females from early mammary tumor development (the primary pathology in Sprague-Dawley rats) and early all-cause mortality. Conversely, lack of reciprocity (whether disproportionately seeking or receiving attempted affiliation) was as potent a risk factor as neophobia. Thus a social role increased risk additively with individual temperament. Our data indicate that affiliative reciprocity functions as a buffer for everyday stressors and are likely mediated by attenuated reactivity of the hypothalamic-pituitary-adrenal axis.
Department of Comparative Human Development, University of Chicago, Chicago, IL 60637, USA. jyee@uchicago.edu
Jason R
JR
Yee
Sonia A
SA
Cavigelli
Bertha
B
Delgado
Martha K
MK
McClintock
D000818:Animals; D003345:Corticosterone / Q000378:metabolism; D004195:Disease Models, Animal; D005106:Exploratory Behavior; D005260:Female; D007030:Hypothalamo-Hypophyseal System / Q000503:physiopathology; D008136:Longevity / Q000502:physiology*; D015674:Mammary Neoplasms, Animal / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control / Q000523:psychology*; D010913:Pituitary-Adrenal System / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012376:Rodent Diseases / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control / Q000523:psychology*; D012380:Role; D012741:Sexual Maturation; D035781:Siblings; D012919:Social Behavior; D012934:Social Isolation; D013315:Stress, Psychological / Q000453:epidemiology / Q000503:physiopathology / Q000523:psychology*
D003345:Corticosterone