Introduction
Understanding the reactions of the pituitary-adrenal system to biologically important stress has recently been of central concern to students of stress physiology. Over the last decade an increasingly large literature adds assurance that psychologically stressful and emotionally disturbing conditions, not involving direct physical insult or injury, do also, though perhaps less greatly, lead to adrenal activation. Response has been reported to such diverse stresses as competitive sports, college examinations, paratroop training, anticipation of surgery, admission to a mental hospital, transfer of monkeys to a new laboratory, intentionally disturbing psychiatric interviews, delayed auditory feedback, disturbing movies, the experience of perceptual distortion, conditioned avoidance and punishment, and numerous other naturally occurring and laboratory-produced conditions. Although the earlier studies had to utilize secondary measures of adrenal activation, newer meth- ods for the measurement of plasma hydrocortisone and urinary hydroxycorticoids provide essentially similar findings. Recent reviews