Perceptual Retraining to Reduce Suicide Risk (PRS)

The study will use a prospective design consisting of three phases. The phases are: the development of the perceptual retraining treatment (PRT), the evaluation of the treatment's feasibility and acceptability, and an assessment of its efficacy. During the third phase, a pilot study will be conducted in which participants will be randomly assigned to either PRT or a waitlist control group in order to assess efficacy. Diagnostic information and eligibility criteria will be assessed using the Structured Clinical Interview for Diagnostic and Statistical Manual (DSM) 4th ed. (SCID) and the Clinician Administered PTSD Scale for DSM-5 (CAPS-5).

This study will use clinical interviews, self-report measures, and behavioral assessments to evaluate the efficacy of the PRT protocol. The study will recruit approximately 30 veterans. The primary inclusionary criterion will be that participants must show some evidence of olfactory perceptual bias toward military-relevant stimuli (e.g., burning rubber, decay, fuel). Investigators are not requiring current suicidal ideation as an entry criterion because investigators believe that a fair percentage of veterans will have some suicidal ideation/intent but making this an entry requirement will limit the investigators ability to recruit given the tight timeline for the study. The study will consist of the development and evaluation of a novel intervention. The essential feature of this intervention is the use of a gradient of triggering smells (e.g., burning rubber, decay, fuel, etc.), to which participants will be systematically exposed in an effort to facilitate habituation to these odors. The PRT protocol will be administered over two 1-hour sessions. Participants will return 1 month after their final PRT protocol session to complete a battery of follow-up measures, as well as the CAPS-5. The primary outcome measures of interest are: olfactory perceptual bias (as measured by the olfactory bias assessment), suicidal ideation and behaviors (as measured by the Beck Suicide Scale and Depressive Symptom Inventory- Suicidality Subscale), and symptoms related to suicide, such as anxiety and trauma (as measured by the Beck Anxiety Inventory and PTSD Checklist for DSM-5, respectively).

The Perceptual Retraining Treatment will involve systematic presentation of diluted malodors. For each individual, vials on either side of their initial ideographic detection threshold will be presented. During the retraining, participants will be given feedback to shift their bias away from the malodorous target stimuli. For example, in the context of diluted solutions participants will be given the feedback that they are "correct" when a "neutral" response is given to solutions that are above the starting threshold (stronger malodor) and "incorrect" when a target is endorsed that is below the starting threshold (weaker malodor). Each training session will consist of 4 training blocks.

Approximately half of the participants will be randomized to the SNT condition designed to control for the effects of time and learning. In the SNT condition, participants will complete the same assessments (including the olfactory bias assessment), as well as a sham training consisting of neutral/neutral odor pairing dilutions, rather than the combat/neutral odor pairings as in the PRT. Following the one-month assessment, they will be given the option to complete the PRT.

Perceptual retraining involves the systematic presentation of diluted malodors (i.e., odors perceived as threatening). For each individual, vials on either side of a pre-determined and ideographic detection threshold will be presented. During the retraining, participants will be given feedback to shift their bias away from the malodorous target stimuli. For example, in the context of diluted solutions participants will be given the feedback that they are "correct" when a "neutral" response is given to solutions that are above the starting threshold (stronger malodor) and "incorrect" when a target is endorsed that is below the starting threshold (weaker malodor).

A participant's ability to detect an array of threatening malodor in neutral dilution gradients will be tested at baseline and after the second and final intervention session (one week after baseline). Perceptual bias is calculated as the percentage of correct responses (i.e., yes or no to detecting the malodor) on an odor over 6 trials for each of the 8 odors, at 25% and 33% dilution (i.e., over 96 trials). Larger positive percentages indicate greater habituation to the malodor, and therefore a training effect toward reducing threat bias (i.e., a positive effect on intervention outcomes).

The Clinician Administered PTSD Scale for Diagnostic and Statistical Manual of Mental Disorders (DSM)-5 (CAPS-5) was administered at the baseline appointment and 1-month follow-up appointment to assess PTSD symptom severity. All 20 of the CAPS-5 items are scored 0-4 and summed to calculate a total score, which ranges from 0-80. Higher scores indicate greater PTSD symptom severity. A difference score was calculated by subtracting the CAPS-5 score at 1-month from baseline, and averaged across each condition; thus, higher (positive) change scores are indicative of increases in PTSD symptom severity, whereas lower (negative) change scores are indicative of decreases in PTSD symptom severity.

The Depressive Symptom Inventory - Suicidality Subscale (DSI-SS) was administered at the baseline appointment and 1 month follow-up appointment to assess the severity of thoughts related suicidal ideation. All four items of the DSI-SS are scored on a 0-3 scale, with total possible sum scores ranging from 0-12; higher scores indicate greater severity of suicidal ideation. For the outcome measure reported, a difference score was calculated by subtracting DSI-SS scores at 1 month from DSI-SS scores at baseline, and averaged across conditions. DSI-SS change scores of zero reflect no change from baseline to 1 month.

The Beck Suicide Scale (BSS) was administered at the baseline appointment and 1-month follow-up appointment to assess thoughts and behaviors related to suicidal ideation, desire, and attempts. The BSS comprises 21 items rated on a 0-3 scale. The first 19 items are sum scored with total possible scores ranging from 0 - 38, with higher scores indicating greater severity of suicide risk. A difference scores was calculated by subtracting the BSS score at 1 month from BSS scores at baseline. Mean change scores of 0 reflect no change in BSS scores from baseline to 1 month.

The Beck Anxiety Inventory-II (BAI) was administered at the baseline appointment and 1-month follow-up appointment to assess symptom severity associated with anxious arousal. The BAI comprises 21 items rated on a 0-3 scale, which can be sum scored to calculate total scores ranging from 0 - 63. Higher scores on the BAI are indicative of greater anxious arousal. A difference scores was calculated by subtracting the BAI score at 1 month from BAI scores at baseline; thus, higher (positive) change scores are indicative of increases in anxious arousal, whereas lower (negative) change scores are indicative of decreases in anxious arousal.

Inclusion Criteria: evidence of olfactory perceptual bias toward military-relevant stimuli (e.g., burning rubber, decay, fuel). military combat exposure in Operation Iraqi Freedom, Enduring Freedom, or New Dawn. Age 18-60. Exclusion Criteria: Significant medical illness that compromises olfactory perception or tolerance (e.g., significant olfactory disease or dysfunction, cardiovascular disease, respiratory disorders, renal disease, epilepsy, stroke, and uncontrolled hypertension or migraines). Evidence of imminent suicidal intent Evidence of current or past psychotic-spectrum disorders, or uncontrolled bipolar disorder. English speakers.