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Prolonged Exposure (PE) is an evidence-based front-line treatment for PTSD that can suffer from high rates of dropout (e.g., around 50% in some real-world clinical settings; Rutt et al., 2018). Due to high dropout rates, providers of PE therapy can sometimes find themselves feeling like Goldilocks and the scheduling puzzle: weekly sessions can feel like too much time when client engagement can wane, but twice weekly sessions may feel like too little time to complete homework.  In our recently published meta-analysis in JOTS, our research team found that scheduling twice-weekly PE sessions was associated with lower dropout rates. 
My co-authors and I systematically identified and reviewed all published randomized controlled trials (RCTs) of PE paying special attention to dropout rates and frequency of treatment. When we examined the relationship between PE frequency and dropout rate across 35 RCTs with 1,508 adults, we found that prescribing PE sessions at least twice weekly was associated with a significantly lower dropout rate compared with prescribing PE sessions less frequently (i.e., 21% vs 34%). 

We also looked at other characteristics that may influence dropout and found that PE prescribed twice weekly remained a significant predictor of lower dropout rates even after controlling for a number of characteristics at the study level (e.g., demographics, clinical characteristics, study characteristics, and study quality).
However, while we conducted a thorough review of the literature and applied rigorous analyses, we were limited in the ability to speak to client experiences that may impact dropout rates, such as childhood trauma or diagnosis of a co-morbid personality disorder. Additionally, we were interested in how other important factors (e.g., race, ethnicity, sexual orientation, employment status, disability status, marital status) may also impact dropout rates, but insufficient reporting by published studies precluded exploration of how these factors affect dropout rate. 
Nevertheless, findings from this meta-analysis suggest that prescribing PE at least twice weekly is associated with clinically meaningful reductions in dropout, suggesting a path forward for both research and clinical practice to reduce dropout rates. 
Across community, academic, and federal health care contexts, mental health providers are under increasing pressure to meet increased demand for mental health services and to deliver measurable results. Given this pressure, twice-weekly sessions, at least at first glance, may seem daunting and unrealistic. However, twice-weekly sessions may actually increase the number of clients able to receive effective, full doses of trauma-focused care (Berke et al., 2019; Rutt et al., 2018).  In addition, twice-weekly sessions may help mental health providers better manage patient/client waitlists and improve access to care, especially if paired with measurement-based care strategies. In research studies, twice-weekly sessions may improve RCT recruitment goals. However, one important consideration for community providers is the higher weekly cost of therapy and other related costs (e.g., transportation) incurred by clients. 
Though multiple factors predict dropout, including ones that are hard to quantify (e.g., reliability of transportation or childcare), session frequency is a relatively accessible and tangible change that can be made. PE therapy already requires collaborative treatment planning between provider and client (e.g., creating an exposure hierarchy specific to client’s life experiences and resources); including session frequency as part of this collaborative approach is not only convenient, but may also help clients achieve a clinically meaningful milestone: successful completion of PE. 

Target Article 

Levinson, D.B., Halverson, T.F., Wilson, S.M., & Fu, R. (2021) Less dropout from prolonged exposure sessions prescribed at least twice weekly: A meta-analysis and systematic review of randomized controlled trials. Journal of Traumatic Stress, 1-13. https://doi.org/10.1002/jts.22822

Discussion Questions

  • How might increasing session frequency reduce treatment obstacles and dropout?
  • When having a collaborative discussion with clients around session frequency, what may be some factors that increase client motivation for twice-weekly sessions? What potential barriers should we be mindful of when asking clients to participate in twice-weekly sessions?
  • What additional research is needed to recommend twice-weekly PE sessions more definitively? 

About the Authors

Daniel Levinson, PhD is a staff psychologist in the VA Healthcare System.  Daniel received his BS from Stanford University and his PhD in Clinical Psychology from the University of Wisconsin-Madison.  His published research addresses topics such as PTSD and mindfulness.
Tate Halverson, PhD is an advanced research fellow at the Mid-Atlantic Mental Illness Research, Education, and Clinical Center (MIRECC) at the Durham Veterans Affairs Healthcare System. Tate completed her PhD in Clinical Psychology at the University of North Carolina at Chapel Hill. Her research centers on reducing self-directed violence in veterans and individuals with serious mental illness (SMI). 
Sarah Wilson, PhD is an investigator in the VA Health Services Research and Development Center of Innovation to Accelerate Discovery and Practice Transformation. She is a practicing psychologist at Durham VA Health Care System and an Assistant Professor at Duke University School of Medicine. Her research focuses on testing and implementation of interventions for substance use, psychological symptoms, and health behavior change in historically oppressed populations, including low-income individuals, sexual- and gender-diverse individuals, and Black, Indigenous, and People of Color (BIPOC).
Rongwei (Rochelle) Fu, PhD is a professor of Biostatistics at the Oregon Health & Science University-Portland State university School of Public Health and has more than 250 peer-reviewed publications. She has provided statistical support and methodology development for more than 100 systematic reviews, and led and participated in methods workgroups to develop and update guidance for quantitative synthesis of comparative effectiveness and diagnostic tests for Agency of Healthcare quality and Research.

References Cited

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Pilling, S., Riggs, D. S., Roberts, N. P., & Shapiro, F. (2019). The International Society for
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Rutt, B. T., Oehlert, M. E., Krieshok, T. S., & Lichtenberg, J. W. (2018). Effectiveness of Cognitive
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