Trial Outcomes & Findings for Effects of Arousal and Stress in Anxiety (NCT NCT00026559)

All sub-studies were conducted at different time points so subjects had the option to participate in multiple sub-studies

Effects of Arousal and Stress in Anxiety

Subjects participated in go/no go (GNG) task condition during periods of threat of shocks and periods of safety when no shock could be administered. During the GNG stimuli were presented on a monitor. In the GNG task, participants were asked to respond to frequent 'go' stimuli ('=') by pressing the '2' on the keypad of a computer keyboard and to withhold their response to infrequent 'nogo' stimuli ('O'). Stimuli were randomly distributed. A correct go hit was a response recorded during these 2000 millisecond (ms) to a go trial. Similarly, a correct nogo omission was a no response during the same period to a nogo trial. Performance was determined for each condition (threat, safe) and trial type (go, nogo) by dividing the number of correct response by the total number of each trial type.

Subjects participated in go/no go (GNG) task condition during periods of threat of shocks and periods of safety when no shock could be administered. During the GNG stimuli were presented on a monitor. In the GNG task, participants were asked to respond to frequent 'go' stimuli ('=') by pressing the '2' on the keypad of a computer keyboard and to withhold their response to infrequent 'nogo' stimuli ('O'). Stimuli were randomly distributed. A correct go hit was a response recorded during these 2000 millisecond (ms) to a go trial. Similarly, a correct nogo omission was a no response during the same period to a nogo trial. Performance was determined for each condition (threat, safe) and trial type (go, nogo) by dividing the number of correct response by the total number of each trial type.

Correct go responses were go trials followed by button press. Mean reaction time (RT) was calculated for correct-go to evaluate speed-accuracy trade-off.

The startle reflex was elicited with a 103-decibel (dB) white noise (40-ms duration) delivered via headphone. The eyeblink component of the startle reflex was recorded binaurally with two AgCl electrodes placed under the left eye. The peak startle/eyeblink reflex magnitude was determined in the 20-100 ms timeframe. The shock was administered either on the left wrist or on the left middle and ring fingers, depending on where the desired intensity was reached. Startle stimuli were delivered between two go trials and go trials that followed a startle stimulus were not included in the analysis. A shock was delivered in two of the four threat blocks in each sequence, just prior to the last go trial, which was not included in the analysis (for a total of 4 shocks). Shock could be administered only in the threat condition and never in the safe condition. The results were analyzed using a Condition (safe, threat) x Task (task, no task) repeated ANOVA.

Subjects retrospectively rated their level of anxiety using a scale of 1-10 where 1 = "not at all anxious" and 10 = "extremely anxious" at the end of each block of a sequence for a total of eight blocks. A block was defined as a combination of a condition (safe or threat) and a task (task or no task). The results were analyzed using a Condition (safe, threat) x Task (task, no task) repeated ANOVA.

Subjects completed the Attention Control Scale (ACS) prior to start of the study. The ACS is a 20-item self-report scale that measures attentional focusing (9 items) and attentional shifting (11 items) rated on a four-point likert scale from "1 - almost never" to "4 - always" with total score range of 20 to 80. Higher score on ACS reflect better ability to direct and maintain attention.

The level of anxiety was assessed using the Trait Anxiety Inventory questionnaire. The Trait Anxiety Scale (T-Anxiety) evaluates relatively stable aspects of "anxiety proneness", including general states of calmness, confidence, and security. The Trait Anxiety Scale has 20 items. All items are rated on a 4-point scale: 1 = almost never, 2 = sometimes, 3 = often, and 4 = almost always.. The scale has a minimum score of 20 and a maximum score of 80. Higher score indicates greater anxiety. Trait Anxiety score was measured prior to start of the study.