Vulnerability and defensive reactions in relation to the human menstrual cycle.

The effects of alterations of the organism's internal state, attributable to the menstrual cycle, upon heart-rate responsivity and conditioning are reported. Two groups of 24 female phobic patients (one with natural cycles and the other taking the oral contraceptive) were tested, either premenstrually or intermenstrually, using a conditioning procedure in which a small blue light was the CS and white noise the UCS. Subjects tested premenstrually were significantly differentiated from those tested intermenstrually respecting HR responsivity to the first UCS. Significant differences were also found in conditioned responses following three acquisition trials. The type of reactions observed are similar to those which have been called defensive reactions. Subjects taking the oral contraceptives showed increased susceptibility to acquisition of conditioned responses.