Quantifying Clinical Case Formulation: Person-Specific Dynamic Network Modelling of Posttraumatic Stress Disorder (PTSD)

Background. Research on posttraumatic stress disorder (PTSD) often relies on nomothetic (group-level) data to infer idiographic (person-level) processes, limiting its clinical relevance. While idiographic studies do capture individual dynamics, they lack a theoretical framework that enables generalization beyond single cases. This study aimed at bridging this gap by operationalizing Ehlers and Clark’s cognitive model of PTSD within an idiographic network framework.Method. In Study 1, a large simulation analysis determined the minimum data requirements for reliably testing model-derived hypotheses. Study 2 applied this approach to intensive longitudinal data from trauma-exposed individuals. Fifty-five participants (31 diagnosed with PTSD, 24 with clinical-level symptoms) provided personalized items reflecting higher-order components of the model—negative appraisals, trauma memory, triggers, sense of current threat, and maladaptive strategies. A subsample of 41 individuals (23 diagnosed, 18 clinical-level symptoms) completed a 3-week Ecological Momentary Assessments (EMA), yielding 2,594 observations (M=63.2 ± 32.1 per participant over 22.8 ± 10.6 days). We applied various nested network algorithms to explore dynamic PTSD mechanisms.Results. We found strong empirical support for the Cognitive Model’s core assumptions, particularly the central role of sense of current threat and its robust associations with trauma memory, negative appraisals, matching triggers, and maladaptive strategies. Cluster analyses of individual networks revealed four common PTSD formulation profiles: threat reactivity, cognitive, re-experiencing, and trigger-threat subtype.Conclusions. These findings demonstrate how idiographic network analysis can extend beyond single-case formulations to identify reproducible clinical patterns. Integrating theoretically grounded constructs with individualized data collection offers a scalable path toward bridging research and practice in PTSD.