Posttraumatic stress disorder is a highly invalidating disorder. Research suggests cognitive processes to play an important role in determining the consequences of stressors on functioning in daily life. At the same time, however, compared to other mental health problems (e.g., major depressive disorder) relatively little is known regarding the involvement of cognitive processes, among which rumination and related factors, in the development and maintenance of posttraumatic stress symptoms and comorbid complaints. The current project aims to model the involvement of cognitive processes in the development and maintenance of posttraumatic stress symptoms, working towards an integrative framework, for the purpose of which we will be relying on a network analytical and experimental psychopathological approach. In addition, the project aims to gain a better understanding of the mechanisms underlying effects of treatment of posttraumatic stress.