Positive and negative consequences of military deployment to Afghanistan.

Anxiety disorders may be the result of learned fear through the process of
classical conditioning. In classical conditioning, a neutral stimulus is paired
with a neutral, unconditioned stimulus (US), which causes fear. When the
neutral stimulus gets associated with the US, the neutral stimulus itself
provokes fear as a conditioned stimulus (CS), triggering the expectancy of the
US. This process is called expectancy learning. Expectancy of the US, and
consequently fear associated with the CS, is thought to extinguish if the CS is
no longer associated with the US. This can be achieved by exposure to the CS
without the US or by exposure to the US alone. A recent breakthrough in de
understanding of fear is that fear extinction results from new learning (Cs-no
US), instead of elimination of the original fear association. This new learning
is referred to as inhibitory learning. Another process in classical
conditioning is evaluative learning, which refers to a change in the intrinsic
valence of the neutral stimuli in a US-valence congruent direction. Individual
differences in both evaluative conditioning and expectancy learning may play an
important role in the development and maintenance of PTSD. More specifically,
this is thought to involve a larger US-expectancy bias during acquisition,
reduced extinction of the US-expectancy, and larger hedonic shifts in the
evaluation of the CS.

In the current study we will prospectively investigate whether pre-trauma
differences in expectancy learning and evaluative conditioning, and posttrauma
differences in inhibitory learning predict PTSD symptoms at follow-up. A larger
US-expectancy bias during acquisition and extinction, and stronger evaluative
conditioning may be pre-trauma vulnerability factors for the development of
PTSD.

Prospective study including a pre-assessment, post-assessment, and follow-up.
In the first assessment, participants are administered computer tasks, starting
with the differential conditioning task consisting of six phases: the stimulus
selection phase, habituation phase, acquisition phase (pairing of CS+ to US,
CS- to no US), extinction phase (presenting CS without US). The conditioning
task is followed by an affective priming task to measure evaluation of the CS,
and finally a US-expectancy bias task. In the second assessment, a similar
conditioning task (*inhibitory learning task*) will be administered, consisting
of a habituation phase, acquisition phase, and transfer of inhibition phase.
During all assessments, participants are administered questionnaires. At the
second and third assessment, a semi-structured clinical interview takes place
(SCID; PTSD and Axis-I disorders).

The burden consists of 8 mild electrical stimuli (500 ms, 0.2-4.0 mA) during
the conditioning task and two brief loud burst of noise (500 ms, 95 dB) during
the expectancy bias task, which will be completed before deployment. During the
inhibitory learning task administered after deployment the burden consists of
12 mild electrical stimuli (500 ms, 0.2-4.0 mA) as well as 45 brief bursts of
noise (40 msec, 108 dB). Possibly, the participant could have an excessive fear
reaction on the electrical stimulus. However, using a work-up procedure, the
stimulus is set at an individual level that is *unpleasant and demanding some
effort to tolerate, but not painful*. The stimuli are not dangerous. These
procedures are used worldwide without any aversive reactions. The loud noise
could be fearful for some participants. There could be some inconvenience while
filling in the questionnaires about psychological complaints, personality and
anger. The participant can choose to not fill in the question. The participant
could get upsetdescribing deployment related traumatic events. In case of
undesirable emotional reactions, the researcher or assistant will be available
to provide help.