Background. The wildfires on May 1, 2016 in Fort McMurray, Alberta (Canada), destroyed approximately 2,400 homes and buildings and led to massive displacement of approximately 88,000 people. Many individuals faced direct or potential threat to their life or health, or significant losses, and many months later, families were still living through ongoing adversity and uncertainty as they adapted to new or temporary homes, schools and workplaces. Alberta Health Services estimated in August 2016 that mental health staff in the city had received 20,000 referrals since May, compared to 1,200 referrals each year.

Objectives. The overarching aim of this project is to understand the needs of the Fort McMurray population in terms of mental health and to widely disseminate evidence-based tools to promote resilience. More specifically, we will assess the efficacy of an online self-help intervention targeting post-traumatic resilience on specific symptoms (post-traumatic stress disorder [PTSD], insomnia, depression).

Method. 1,510 phone surveys have been conducted in May-July 2017 to assess the prevalence of PTSD, insomnia and depression in the evacuees from the Fort McMurray wildfires (T0). After the survey, 697 participants expressed interest to participate in the longitudinal arm of the study, which will include four in-depth assessments with online questionnaires (T1 to T4) and a diagnostic interview (T1 only). A period of six months will separate all four times of assessment. Participants with post-traumatic stress symptoms (expected n = 150) will be randomised either to the treatment condition (n = 75) or to a waitlist control condition (n = 75) after completion of T2.

Data Analyses. Primary outcomes will be post-traumatic, depressive and insomnia symptom severity, measured with validated self-report questionnaires. Secondary outcomes will include cognitive, behavioural and social indicators, as well as general mental health and post-traumatic growth. Several probable moderators of treatment will be examined, including sociodemographic characteristics, level of exposure, and continuing stressors.

Foreseen Impacts. If found effective in reducing symptoms, the results of this study have the potential to impact positively the Fort McMurray community. Indeed, a direct and concrete deliverable of this research project will be to provide an extended (at least two years) and free access to the online intervention specifically tailored to this population's needs.

Inclusion Criteria:

• Significant post-traumatic stress symptoms (PCL-5 ≥ 23) OR
• Some post-traumatic stress symptoms (PCL-5 ≥ 10) with at least mild depressive symptoms (PHQ-9 ≥ 5) and/or subclinical insomnia symptoms (ISI ≥ 8).