Method: A PAI model developed by Deisenhofer et al. (2018) was used to predict treatment outcomes in a statistically independent dataset including archival records for N = 152 patients with PTSD who accessed either trauma-focussed cognitive behavioural therapy or eye movement desensitisation and reprocessing in routine care. Outcomes were compared between patients who received their PAI-indicated optimal treatment versus those who received their suboptimal treatment.

Results: The model did not yield treatment specific predictions and patients who had received their PAI-indicated optimal treatment did not have better treatment outcomes in this external validation sample.

Conclusion: This PAI model did not generalise to an external validation sample.

Clinical or methodological significance of this article: Due to individual differences, some patients with post-traumatic stress disorder may be more likely to benefit from one evidence based psychological therapy than another. Using machine learning methods, it may be possible to identify these patients prior to the start of treatment and make an informed treatment recommendation. However, this study highlights the importance of external validation of machine learning models as an essential prerequisite to the clinical testing of such models in psychotherapy practice.”