Conditioning cortisol and its psychophysiological effects

Preliminary evidence suggests that it might be possible to condition endogenous
cortisol, with subsequent psychophysiological effects. In a pilot study for the
current study, medium to large effect sizes were found for conditioned effects
on endogenous cortisol levels and other psychophysiological outcomes. When more
systematic research in a sufficiently powered sample would support these
findings, the ability to condition cortisol could offer new therapeutic
possibilities.

To investigate the effects of conditioning with hydrocortisone on endogenous
cortisol. Effects of conditioning on endogenous cortisol in response to a
validated short-term psychosocial stress task and other psychophysiological
outcomes will also be explored. Additionally, the possible influence of the
5-HTTLPR genotype and possible other genetic variants on the effects of
conditioning will be explored.

In line with previous conditioning studies as well as the previously conducted
pilot study by the research group, a randomized placebo-controlled conditioning
paradigm consisting of 2 phases will be applied. In the acquisition phase,
consisting of 3 sessions on 3 consecutive days, an association between an
unconditioned stimulus (experimental condition: hydrocortisone pill; control
condition: placebo pill) and a conditioned stimulus (novel tasting beverage)
will be established. In the evocation phase, also consisting of 3 sessions on 3
consecutive days a week after the acquisition phase, all participants will be
administered a placebo pill paired with the same beverage as in the acquisition
phase. In the acquisition phase, baseline measurements of cortisol,
alpha-amylase, and self-reported well-being will be taken in each session. In
the evocation phase, cortisol, alpha-amylase, and self-reported well-being will
be measured at several time points, and heart rate and skin conductance will be
monitored continuously. In each evocation session, participants will also be
asked to perform some cognitive filler tasks and during the last session
participants will be exposed to a validated short-term psychosocial stress
task. Successful conditioning would be shown by a conditioned response (change
in endogenous cortisol) after exposure to the conditioned stimulus (the
beverage paired with a placebo pill) in the evocation phase. Additionally, the
study will explore whether conditioning of cortisol has effects on other
psychophysiological outcomes such as autonomic functioning and well-being.

In the experimental group, cortisol is elevated exogenously on three
consecutive days by administration of 100 mg hydrocortisone.

Participants need to invest 1,5 hours for the first session. The 3 acquisition
sessions will take approximately 15 to 20 minutes and each of the evocation
sessions lasts on average 2,5 hours. This results in a total time investment of
ca. 10 hours across three weeks. During the acquisition phase, 100 mg of
hydrocortisone will be administered to half of the participants on three
consecutive days. Given the safety outcomes of our pilot study, the short
half-life of hydrocortisone (8-12 hours), and the administration of only 3
doses, no adverse side effects are expected (although they will naturally be
monitored), especially as this study is conducted in healthy individuals. Also,
all participants will be asked to perform some cognitive filler tasks and will
be exposed to a validated short-term psychosocial stress task during the last
session. Subjects will receive a reimbursement of ¤150,- for participation in
this study.