Suppressing the morning rise in cortisol impairs free recall.

Elevated glucocorticoid levels impair memory retrieval. We investigated whether retrieval under naturally elevated glucocorticoid levels, i.e., during the morning rise in cortisol can be improved by suppressing cortisol. In a crossover study 16 men retrieved emotional and neutral texts and pictures (learned 3 d earlier) 30 min after morning awakening, following administration of the cortisol synthesis inhibitor metyrapone or placebo. Unexpectedly, the metyrapone-induced cortisol suppression significantly impaired free recall of both materials. Recognition remained unaffected. Thus, not only high, but also very low glucocorticoid levels impair retrieval, with the latter effect possibly reflecting insufficient occupation of hippocampal/amygdalar mineralocorticoid receptors (MRs).