RecruitingBehavioural interventionAccelerated Treatment for Co-occurring Insomnia, Nightmares, and PTSDThis study is a two-arm individually randomized group treatment clinical trial evaluating behavioral therapies for insomnia, nightmares, and PTSD. The study will compare cognitive-behavioral therapy for insomnia and nightmares to sleep hygiene (Control), both integrated with Written Exposure Therapy for PTSD and delivered in an accelerated (i.e., 5-day) group treatment format, preceded and followed by individual treatment sessions. 160 participants will be randomized into one of two study conditions.