Two studies investigated the association between cortisol levels and memory performance in healthy adults. In a first study, 13 subjects were exposed to a brief psychosocial laboratory stress (“Trier Social Stress Test”) with a subsequent test of declarative memory performance. Results indicated a significant negative relationship between stress-induced cortisol levels and performance in the memory Task, I.e. subjects with high cortisol response to the stressor showed poorer memory performance. In a second experiment it was investigated if cortisol alone, i.e. independent of psychological stress, would also impair memory function. In this study, 40 healthy subjects received either 10 mg cortisol or placebo orally. One hour later they were tested for procedural and declarative memory and spatial thinking. Subjects who received cortisol showed impaired performance in the declarative memory and spatial thinking tasks but not in the procedural memory task. From these results we conclude that in healthy adults elevated free cortisol levels are associated with impaired memory function.
Kirschbaum, C., Wolf, O. T., May, M., Wippich, W., & Hellhammer, D. H. (1996). Stress-and treatment-induced elevations of cortisol levels associated with impaired declarative memory in healthy adults. Life sciences, 58(17), 1475-1483.