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The figure shows the results a Trier test using three different measures of stress. All three parts of the figure are line graphs in which the horizontal axis is labelled time and is marked in minutes from minus 15 to 90 at intervals of 15 minutes. The test period was from zero to 30 minutes. The vertical axis in part (a) is labelled mean ACTH level in blood and is marked from zero to 16 at intervals of 2 arbitrary units. The vertical axis in part (b) is labelled mean cortisol level in blood and is marked from zero to 550 at intervals of 50 arbitrary units. The vertical axis in part (c) is labelled mean heart rate and is marked from 55 to 95 at intervals of 5 beats per minute. In each part of the figure there are 4 lines plotted, corresponding to the 4 groups of participants: ELS/MD; ELS/no MD; no ELS/MD; and controls. The number in each group was between 10 and 14. All groups showed some rise in stress level in response to the test, with the level returning to around its pre-test value within an hour of completion of the test. On all three stress measures, the largest rise was in the ELS/MD group. A significant rise in ACTH also occurred for the ELS/no MD group, but not in the no ELS/MD and control groups. The cortisol increases in the ELS/no MD group, no ELS/MD and control groups were very similar and substantially lower than in the ELS/MD group: cortisol in the ELS/MD group rose from a mean of 150 to peak at 450 units, while in each of the three other groups, it rose from similar starting values to reach a maximum of around 300 units. Starting heart rates were around 75 beats per minute in the three experimental groups, and around 70 beats per minute in the control group. Heart rate in the ELS/MD group reached just over 85 beats per minute, while rates in the ELS/no MD and no ELS/MD groups both rose to levels of about 78 beats per minute; heart rate in the control group increased only slightly, to 72 beats per minute. Interestingly, the heart rate of the latter group had dropped to 62 beats per minute by the end of the experiment.

 1.3  Early life events and stress