Comparing Heart Rate Analytical Methods to Examine Engagement During Imaginal Prolonged Exposure Therapy: Multicase Study.

Objective: As mobile health technologies proliferate, their use during exposure-based therapies has the potential to illuminate treatment mechanisms. The primary purpose of this study was to examine three approaches to using continuously collected physiological data of patients with posttraumatic stress disorder during prolonged exposure (PE) therapy, in an effort to examine physiological markers of treatment response.

Methods: Photoplethysmogram-measured heart rates from three non-Hispanic White male veterans, during clinic-based PE therapy sessions, were analyzed to assess three potential therapeutic mechanisms: emotional engagement (examined via correlation analysis between self-reported peak distress ratings and objectively measured peak heart rate in the minute prior to distress ratings), initial emotion activation (examined through time to peak heart rate and peak self-reported distress), and extinction processes within and between therapy sessions (examined via multilevel modeling of within- and between-person changes in heart rate over time and across imaginal PE therapy sessions).

Results: Results for each analytical approach with each patient are presented, and benefits and limitations of each approach are discussed. Treatment outcomes were as follows: one participant with overengagement did not benefit from PE, one participant with initial underengagement demonstrated clinical improvement, and one participant with optimal engagement had associated clinical improvements.

Conclusions: Mobile health technologies may provide a new avenue toward unveiling treatment mechanisms in psychotherapy. Use of standardized analytical approaches will enable cross-study comparison and greater understanding of treatment mechanisms, ultimately leading to increased treatment response.