Abstract
Background: Even though evidence-based treatments are generally effective in reducing post-traumatic stress disorder (PTSD) in youth, many still experience elevated symptoms after treatment. A better understanding of how PTSD develops throughout treatment can increase efficiency and reduce residual symptoms.Objective: This study investigated which PTSD symptom clusters and symptoms within these clusters changed the most and least through trauma-focused cognitive behavioural therapy (TF-CBT), and identified common residual symptoms after treatment.Method: Latent growth curve modelling was used to identify differences in intercepts and slopes of symptoms, and residual symptoms were identified with McNemar tests in a sample of 517 youth (aged 6-19 years, 75.6% girls) receiving TF-CBT.Results: We found small but statistically significant differences in slopes across clusters. Avoidance both reduced the most and demonstrated most residual symptoms. Also, within clusters, many of the symptoms that reduced the most, such as psychological cue reactivity, persistent negative emotional state, and difficulties sleeping and concentrating, had the highest symptom levels before treatment and the most residual symptoms after treatment.Conclusions: Overall, symptoms of PTSD were reduced throughout TF-CBT. Symptoms rated highest at treatment start decreased the most but also tended to persist as common residual symptoms. Symptoms such as psychological cue reactivity, persistent negative emotional state, and negative beliefs that were common residual symptoms and are known to be central in the development and maintenance of PTSD are of particular clinical relevance. Research based on frequent symptom measurements during treatment could capture subtler changes, increasing understanding of the mechanisms of effective trauma treatment.