Effects of Psychic Stress on Atherosclerosis in the Squirrel Monkey (Saimiri sciureus).

SummaryTwo groups of squirrel monkeys (Saimiri sciureus) were subjected to intermittent stress of different types (restraint alone and restraint combined with conditioned avoidance) for a period of 25 months. The following statistically significant differences were observed between the test groups and a control group of monkeys confined to cages for the same period of time: (1) The mean serum cholesterol was higher following the periods of stress; (2) excretion of urinary 17-ketosteroids was increased; and (3) coronary artery atherosclerosis was more marked. Although no significant differences were observed in the weight of the adrenal glands, the adrenals from all except one of the test monkeys showed changes observable grossly and histologically. Electrocardiographic changes, present in 4 of the test monkeys, were not seen in any monkeys in the control group. The effects of stress-liberated catecholamines are discussed briefly.