[Psychosocial factors as predictors of atherosclerosis and cardiovascular events: contribution from animal models].

Conventional risk factors (abnormal lipids, hypertension, etc.) are independent predictors of atherosclerosis and cardiovascular events; however, these factors are not specific since about half patients with acute myocardial infarction paradoxically result at low cardiovascular risk. Recent prospective studies provide convincing evidence that some psychosocial factors are independent predictors of atherosclerosis and cardiovascular events, as well. Psychosocial factors that promote atherosclerosis can be divided into two general categories: chronic stressors, including social isolation/low social support and work stress (subordination without job control) and emotional factors, including affective disorders such as depression, severe anxiety and hostility/anger. The emotional factors, such as the chronic stressors, activate the biological mechanisms of chronic stress: increased activity of the hypothalamic-pituitary-adrenal axis, sympathetic system and inflammation processes, which have atherogenic effects, and an increase in blood coagulation. In spite of the amount of published data, psychosocial factors receive little attention in the medical setting. About 30 years ago, Kuller defined the criteria for a causal relation between a risk factor and atherosclerosis and cardiac events. The first of these criteria states that experimental research should demonstrate that any new factor would increase the extent of atherosclerosis or its complications in suitable animal models. We carried out a bibliographic research in order to investigate whether the results of the studies dealing with animal examination and experimentation support the psychosocial factors as predictors of atherosclerosis. Contributions related to some of the psychosocial factors such as social isolation, subordination and hostility/anger have been found. In these studies atherosclerotic extension has been evaluated at necroscopy; however, the incidence of cardiovascular events has not been investigated. As regards the biological mechanisms of chronic stress, the hypothalamic-pituitary-adrenal axis and the sympathetic system have been investigated. The studies have mainly been carried out on primates, and, to a less extent, on other mammals such as rabbit and wolf and on some species of birds. In the animals under social isolation, subordination or hostility/anger, a significantly more severe atherosclerosis was present, besides an increased activity of the hypothalamic-pituitary-adrenal axis and sympathetic system. In conclusion, the results offered by animal models seem to satisfy the first of Kuller's criteria, as for the three above-mentioned psychosocial factors.