Study aim: To determine the efficacy of cognitive processing therapy in post-traumatic stress disorder (PTSD). To identify the mechanisms of symptom change during treatment using idiographic dynamic network analysis. Design: The clinical trial has a control group, with parallel groups, single-blinded and randomized on 45 patients. For randomization, the random block method will be used by selecting the sequence of each block using R or Excel software. Settings and conduct: The location will be in the university clinic. First, a pre-test and then an individual network analysis will be conducted. The intervention will be for the experimental group and continued evaluation, and finally a post-test will be taken and analyzed. Blinding will be for the analysts and the statistical analysis section. Participants/Inclusion and exclusion criteria: Inclusion criteria for the study included: 1. Diagnosis of post-traumatic stress disorder 2. No history of participating in cognitive processing therapy 3. No substance use disorder 4. Minimum age 18 years 5. Minimum literacy 6. No chronic psychiatric disorders such as bipolar disorder, psychosis spectrum disorders, and serious suicidal thoughts Exclusion criteria included: 1. Failure to participate in more than 3 therapy sessions 2. Newly started psychotherapy or during treatment 3. Failure to complete more than 50% of the questions in the individualized network analysis section Intervention groups: Intervention group received cognitive processing therapy Usual control group received treatment at the end of the study Main outcome variables: The outcome of the study is to examine the network of individual symptoms and the effectiveness of cognitive processing therapy.