Effects of major depression diagnosis and cortisol levels on indices of neurocognitive function

Although many studies have examined separately the effects of depression and cortisol on cognition, no study has examined their relative or potentially additive effects. Our study simultaneously investigated the contributions of clinical status [major depression (MD) versus psychiatrically healthy controls (HC)] and cortisol on a hippocampal/mediotemporal mediated verbal memory task (Paragraph Recall) and a prefrontal cortex/cingulate mediated executive functioning task (Stroop). Thirty-seven unmedicated nondelusional MDs and 18 HCs underwent psychiatric ratings, hourly assessments of cortisol activity over 24 h, and neuropsychological assessments. Hierarchical multiple regressions indicated a significant effect of cortisol but not of diagnosis on verbal memory. Greater cortisol levels were related to poorer memory performance independent of group. In contrast, a significant interaction between cortisol and diagnosis was found for a color-word index of response inhibition. This interaction suggests that the detrimental effect of elevated cortisol level on this type of executive functioning exists only in the healthy control group but not in MDs. On an Interference score, another measure of response inhibition, cortisol had a significant independent effect, but neither the effects of diagnosis and the interaction attained full significance. Our study suggests that cortisol has an independent effect on verbal memory. Also, our study produced evidence of an interaction between diagnosis and cortisol on response inhibition.