Police officers, correctional service officers, and 911-operators are at increased risk for suffering from trauma-related disorders due to their direct and indirect exposure to life-threatening events, such as shootings, violent assaults, or car accidents, among others. Typical treatments for post-traumatic stress disorders include psychotherapy and pharmacological therapies (i.e., antidepressants). Although these interventions are effective for many sufferers, they all have limitations. Thus, the investigators propose to explore the usefulness of a new therapeutic technique, reconsolidation blockade, which involves reactivating the trauma memory while under the influence of propranolol. Objectives and hypotheses: To explore the efficacy and cost-effectiveness of reconsolidation blockade therapy as an adjunct treatment for trauma- and stressor-related disorders as defined in the Diagnostic and Statistical Manual Mental Disorders-5. The investigators hypothesize that, compared to the control group, 5 weekly trauma-memory reactivations under propranolol treatment will confer a significant reduction in trauma-related symptoms and significantly more health-related economic benefits. Stress symptoms and health-related costs will be assessed at 7, 26 and 52 weeks after study inclusion. In this study, the investigators will also explore the effects of reconsolidation blockade with propranolol on various neuropsychological functions.

Inclusion Criteria:

• Understands and reads French
• Currently or previously worked for the Quebec City Police Department, or the 911 dispatch for Quebec City, or another police department or 911 dispatch in the province of Quebec, or for the Quebec Ministry of Public Security as a correctional service officer
• Meets criteria for a trauma-and stressor-related disorder, such as: Acute Stress Disorder, Posttraumatic Stress Disorder, Adjustment Disorder, Other Trauma- and Stressor-Related Disorder, as defined by the Diagnostic and Statistical Manual for Mental Disorders, 5th edition.
• The trauma-and stressor-related disorder must be due to a work-related event.
• A score of at least 4 (moderately ill) on the Clinical Global Impressions-Severity Scale.
• Participants who are currently taking a Selective Serotonin Reuptake Inhibitors or Selective Norepinephrine Reuptake Inhibitors (antidepressants) must accept to skip their morning dose on the days that they receive the study's intervention.

Exclusion Criteria:

• Systolic blood pressure < 100mm Hg (millimeter of mercury) at visit 0.
• Heart rate < 55 bpm (beats per minute) at visit 0.
• Medical conditions that contraindicate propranolol administration, as determined by the treating physician.
• Previous diagnosis of a traumatic brain injury (TBI).
• Previous adverse reaction or non-compliance with a beta-blocker.
• Medications that can have an dangerous interaction with propranolol.
• Fertile women who are not using an adequate contraceptive methods.
• Pregnant women.
• Nursing women.
• The following psychiatric conditions: past or present bipolar disorder, past or present psychotic disorder, present substance abuse or dependence, actively suicidal, past or present neurological disorder, complex posttraumatic stress disorder.