Perhaps because of its simplicity and its appeal to "common sense," the concept that "strain" or "distress" is directly proportional to "stress" in the human is often regarded in medical-psychiatric investigation as an established fact. This formulation would appear to be a legacy from several different sources: from the stimulus-response model in experimental animal psychology, from traditional engineering mechanics (eg, the greater the load or "stress" on a spring, the greater the displacement or "strain" of that spring), and, finally, from what is implied by the infectious disease model in medicine itself (ie, the greater the number of infecting organisms innoculated into a host, the more serious is the ensuing infection likely to

The manifestations of this reasoning are varied. Thus, importance is frequently attached to the fact that certain chronic diseases of unknown etiology (eg, diabetes, colitis, hypertension) may have appeared to begin or to become exacerbated during