BackgroundExposures to “traumatic” events are widespread and can cause posttraumatic stress disorder (PTSD). Cognitive behavioral therapy and eye movement desensitization and reprocessing (EMDR) are frequently used and validated behavioral PTSD treatments. Despite demonstrated effectiveness, highly upsetting memory reactions can be evoked, resulting in extensive distress and, sometimes, treatment dropout. In recent years, multiple treatment approaches have aimed at reducing such upsetting memory reactions to traumatic memories while therapeutic progress proceeds. One of these methods, the flash technique (FT), a modification of standard EMDR (S-EMDR), appears effective in distressing memory reduction. This study will examine FT-EMDR and S-EMDR efficacies when both methods are delivered via web-based video.ObjectiveThis study aims to assess the relative efficacy of (web-based) FT-EMDR versus S-EMDR in reducing the PTSD symptoms, anxieties, and depression associated with traumatic memories at postintervention and 1-month follow-up.MethodsThis double-blinded, web-based, 2-arm randomized controlled trial will employ self-report outcomes. A total of 90 participants will be identified from the web-based CloudResearch platform and randomly allocated to the experimental or comparison group. Inclusion criteria are as follows: (1) approved for engagement by the CloudResearch platform; (2) 25-60 years of age; (3) residing in Canada or the United States; (4) a recalled disturbing memory of an event >2 years ago that has not repeated and was moderately or more upsetting during occurrence; (5) memory moderately or more upsetting at baseline and not linked to an earlier memory that is equally or more than equally disturbing. Exclusion criteria are bipolar disorder, borderline personality disorder, obsessive-compulsive disorder, schizophrenia, substance abuse or addiction in the past 3 months, suicidal ideation, and suicide attempt in the past 6 months. Interventions include guided video instruction of full FT or guided video of EMDR. Outcome measures are as follows: Primary outcome is PTSD symptoms that are measured by the PTSD Checklist for DSM-5 (Diagnostic and Statistical Manual of Mental Disorders-5) at 1-month follow-up. Secondary outcomes are State Anxiety subscale of State-Trait Anxiety Inventory at baseline, postintervention, and 1-month follow-up; Trait Anxiety subscale of State-Trait Anxiety Inventory; depression (Patient Health Questionnaire-9); and Positive and Negative Affect Schedule measured at 1-month follow-up.ResultsIf, at 1-month follow-up, the web-based FT-EMDR intervention is more effective in reducing PTSD symptoms (as measured by the PTSD Checklist for DSM-5) than EMDR, it may help reduce traumatic memory distress in multiple contexts.ConclusionsThis randomized controlled trial will advance current understandings of PTSD symptoms and interventions that target traumatic memory–related distress.Trial RegistrationClinicalTrials.gov NCT05262127; https://clinicaltrials.gov/ct2/show/NCT05262127