Table 2.
Cortisol Levels, Dexamethasone Suppression Test, and Memory for Pictures Encoded during Placebo and Cortisol Administration
| Depression Groups | Depression Group Comparisons |
|||
|---|---|---|---|---|
| Never Depressed (n = 26) |
Other Depression (n = 24) |
Current MDD (n = 15) |
||
| Cortisol levels, μg/dL | ||||
| Morning peak cortisol | 0.60 ±0.24 | 0.58 ±0.27 | 0.57 ±0.26 | F(2,62)=0.09, n.s. |
| Post-dexamethasone morning cortisol | 0.30 ±0.25 | 0.29 ±0.24 | 0.42 ±0.33 | F(2,62)=1.23, n.s. |
| DST feedback sensitivitya | 0.30 ±0.19 | 0.28 ±0.17 | 0.15 ±0.24 | F(2,62)=3.10, p=.05 |
| Memory biasb | ||||
| Placebo | 0.03 ±0.19 | 0.11 ±0.18 | 0.26 ±0.21 | F(2,62)=6.91, p=.002 |
| CORT | 0.07 ±0.19 | 0.10 ±0.17 | 0.11 ±0.22 | F(2,62)=0.23, n.s. |
| Total memoryc | ||||
| Placebo | 24.0 ±9.6 | 22.7 ±6.9 | 20.0 ±5.6 | F(2,62)=1.22, n.s. |
| CORT | 25.0 ±9.0 | 24.3 ±7.6 | 21.5 ±5.1 | F(2,62)=1.05, n.s. |
Values are mean ±SD.
CORT, cortisol administration; DST, dexamethasone suppression test; MDD, major depressive disorder. International System of Units (SI) conversion factors: To convert cortisol to nmol/L, multiply values by 27.588.
DST feedback sensitivity is the difference between morning peak cortisol and post-dexamethasone morning cortisol, with higher numbers reflecting greater DST feedback sensitivity (i.e., greater dexamethasone suppression of cortisol). Groups differed on DST feedback sensitivity, F(2,62)=3.10, p=.05, reflected in the lower feedback sensitivity in the MDD group. However, groups did not differ significantly on absolute morning peak cortisol or post-dexamethasone morning cortisol, p’s>.29.
Memory bias is expressed as a ratio, in which higher numbers reflect more negatively biased memory (see method section for detail). When DST feedback sensitivity is not included in the model, there is a main effect of Group for memory bias, F(2,62)=3.58, p=.03, such that depressed subjects show greater negative memory bias, particularly in the MDD group for pictures encoded during placebo.
There is also a Group X Drug interaction for memory bias, F(2,62)=3.61, p=.03, reflected in the normalization of memory bias in MDD participants for pictures encoded during CORT. See text and Figure 3 for findings when DST Feedback Sensitivity is included in the model. Also see text for analyses with depression treated as a continuous rather than categorical variable.
Total memory refers to values for unpleasant plus pleasant pictures recalled. Effects of CORT (vs. placebo) trended toward facilitation of total free recall, F(1,62)=3.20, p=.078, across all levels of depression severity.