"Flooding in vivo" during the circadian phase of minimal cortisol secretion: anxiety and therapeutic success without adrenal cortical activation.

Seven patients with maximally severe phobias for physical objects were treated by "flooding in vivo", i.e. live confrontation with the feared object. Each reported to the laboratory for 3 hr on five separate occasions, all in the early evening during the circadian phase of minimal adrenal cortical activity. At 20-min intervals during each session, blood was taken for cortisol assay, and anxiety was self-rated on a scale of 0 to 100. Treatment was carried out during the 2nd hr of the third and fourth sessions. The remaining time provided control observations. By behavioral and subjective criteria, the treatment hours produced very intense anxiety. However, they failed to evaluate plasma cortisol levels. The remission of the phobias was 100%. Anxiety, even when intense and dramatic, does not necessarily activate the adrenal cortex, and an adrenal "stress" response is not necessary for the therapeutic effect.