Cortisol Suppression and Startle Responses in Posttraumatic Stress Disorder (PTSD) (CSS)

Effects of Cortisol Suppression on Fear-Potentiated Startle in Traumatized Individuals With and Without PTSD

Posttraumatic stress disorder (PTSD) occurs in some people after exposure to events that cause extreme fear or helplessness. The incidence of war zones worldwide and the prevalence of violence in large cities in the U.S., increases the likelihood that people will experience a traumatizing event in their lifetime. About 1 in 10 people who survive such events will develop PTSD, while most people will get better over time. This suggests that some people may have biological vulnerabilities that make it harder for them to recover. One of these biological risk factors may be related to how stress hormones work in people who get sick. Another is how people react to things that make them afraid or nervous, investigators have found that PTSD patients have higher than normal fear reactions. The part of the brain that reacts to fearful stimulation is linked to stress hormones; the purpose of this study is to examine how these systems interact. The study will suppress stress hormones (cortisol) production in one group of participants, while another will get a placebo. When their cortisol is suppressed, the participants will undergo a startle study to see if their fear responses are decreased. Investigators expect that people PTSD will show a normal fear response when their cortisol levels are reduced, similar to people without PTSD. This research can help discover new medicines for people with PTSD.

The proposed study will provide innovative tools to tease apart the relationship between amygdala-dependent neurophysiology and HPA-axis sensitivity in a human clinical population. Investigators have discovered that cortisol suppression reduces fear responses in PTSD coupled with the development of new fear conditioning paradigms, providing a unique opportunity to interrogate amygdala-HPA interactions to determine aspects of the neurobiological underpinnings of PTSD-related pathology. Aim 1a will examine baseline and fear-potentiated startle (FPS) response, as well as cognitive awareness in PTSD patients and traumatized Non-PTSD controls during a fear conditioning experiment 10 hours after dexamethasone administration in a double-blind, placebo controlled crossover design. Aim 1b will examine the above outcome measures in PTSD patients and controls during a fear conditioning experiment 1 hour after dexamethasone administration in order to control for direct effects of dexamethasone. Aim 2a will examine fear-potentiated startle (FPS) response in PTSD patients and traumatized Non-PTSD controls during fear extinction, when the fear is acquired 10 hours after dexamethasone administration in a double-blind, placebo controlled crossover design. Aim 2b will examine the same outcome measures in PTSD patients and controls, when the fear is acquired 1 hour after dexamethasone administration in order to control for direct effects of dexamethasone.

Participants who do not have PTSD will receive placebo and dexamethasone in random order for the duration of two consecutive study visits separated by at least one month.

Participants with PTSD will receive placebo and dexamethasone in random order for the duration of two consecutive study visits separated by at least one month.

The study measured the acoustic startle response magnitude to a sudden noise using electromyography of the eyeblink muscle. This response magnitude was used as the individual's baseline to compare to the startle magnitude to the danger signal to see if fear conditioning had occurred.

The acoustic startle response magnitude was measured using electromyography recordings of the eyeblink muscle when a sudden tone was delivered through headphones in the presence of a stimulus that was paired with an aversive outcome (i.e. the danger signal). If an individual showed successful fear learning, then startle to the danger signal would be greater than baseline startle.

Fear-potentiated startle was measured as a difference score between the startle to danger signal and the baseline. This difference score reflects the degree of fear response at the beginning of extinction.

This measures the level of fear-potentiated startle (the difference between startle magnitude to the danger signal and baseline startle magnitude) at the end of extinction. Because the danger signal is no longer paired with the aversive stimulus like it was during the conditioning phase, the fear response should decrease from early to late extinction in individuals who show intact extinction learning.

Inclusion Criteria: Able to give informed consent Willing to participate in initial assessment and 2 full days of interviews and imaging visit Able to understand English and no obvious deficit in comprehension or following directions 18-65 years old Exclusion Criteria: Mental Retardation (per clinical judgment of study physician) Psychotic Disorder (per clinical judgment of study physician) Acute suicidal ideation Pregnancy Positive urine drug screen Active medical disorders contributing to psychiatric sx e.g. hypo or hyperthyroidism, SLE, advanced cirrhosis, etc. (per clinical judgment of study physician)

Jovanovic T, Phifer JE, Sicking K, Weiss T, Norrholm SD, Bradley B, Ressler KJ. Cortisol suppression by dexamethasone reduces exaggerated fear responses in posttraumatic stress disorder. Psychoneuroendocrinology. 2011 Nov;36(10):1540-52. doi: 10.1016/j.psyneuen.2011.04.008. Epub 2011 May 20.