RecruitingBehavioural interventionStepped Care for Posttraumatic Stress Disorder StudyLess than 20% of people with PTSD receive any treatment. This study extends a program of research by the investigator focused on developing adaptive (stepped) interventions for PTSD. The adaptive intervention sequences a digital mental health intervention (DMHI) and brief trauma- and skills-focused treatments for PTSD. The selected treatments are brief and scalable and less burdensome to systems of care. These treatments are: web-administered Skills Training in Affective and Interpersonal Regulation (webSTAIR), Brief STAIR, and Written Exposure Therapy (WET).