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Level of Engagement With Smartphone-delivered Psychotherapy Not Linked to Treatment Response

Key findings

  • This secondary analysis of 77 participants in a randomized, wait-list–controlled trial examined patterns of engagement with a cognitive–behavioral therapy app for body dysmorphic disorder (BDD) and which patterns were associated with treatment response
  • 47% of participants were light users, who exhibited low to medium use volume (total minutes/sessions/days), low frequency of use, and consistently short sessions
  • The other patterns were deep users (22%), who exhibited low use volume and low frequency but engaged in longer sessions, and samplers, who exhibited high use volume and frequent use with generally short sessions
  • All three clusters of users improved significantly on the Yale-Brown Obsessive Compulsive Scale Modified for BDD during 12 weeks of treatment, and there were no significant between-group differences
  • The results suggest clinicians need not prescribe a one-size-fits-all engagement approach with smartphone psychotherapies, an important finding since individuals appear to have distinct preferences about how to engage

The development of smartphone-delivered psychotherapies is proliferating quickly, but there are wide gaps in knowledge about how people prefer to engage with these apps. Moreover, the field needs information about which engagement patterns result in treatment responses.

To study these issues, Massachusetts General Hospital researchers conducted a secondary analysis of a randomized, controlled trial of cognitive–behavioral therapy (CBT) for body dysmorphic disorder (BDD). In Internet Interventions, they describe a roadmap for comprehensive measurement and reporting of behavioral engagement.

The authors are Hilary Weingarden, PhD, psychologist and assistant director of Mass General's Center for Digital Mental Health, Sabine Willhelm, PhD, chief of Psychology in the Department of Psychiatry and director of the Center for OCD and Related Disorders, and colleagues.


Trial participants were assigned 1:1 to access the Perspectives app (Koa Health, London, UK) immediately or after 12 weeks on a waitlist. Koa Health sponsored the study.

Perspectives is a coach-guided CBT delivered via smartphone. In the trial, bachelors-level coaches supported engagement and motivation via phone calls (at treatment introduction and midpoint) and brief asynchronous in-app chats each week. Participants were instructed to try to use the app daily for 12 weeks.

84% of participants were female, the mean age was 27, and BDD symptoms at baseline were generally moderate to severe, with a mean score of 28 on the Yale-Brown Obsessive Compulsive Scale Modified for BDD (BDD-YBOCS). 26% of participants met the criteria for major depressive disorder at screening.

Engagement Patterns

Participants engaged with the app frequently, briefly, and for a greater total time earlier in the program:

  • The mean duration of app use was 132 minutes during the 12-week treatment period, and 75% of participants used the app for a cumulative time of more than 63 minutes
  • Participants logged a mean of 43 sessions, with 67% of sessions lasting >30 seconds to three minutes and only 18% lasting more than five minutes
  • 63% of total time on the app occurred during the first four weeks, and 76% occurred during the first six weeks

19 objective engagement variables were derived from phone analytics data. These were reduced via factor analysis into two factors: (1) use volume and frequency and (2) session duration. Cluster analysis based on those factors yielded three engager types:

  • Deep users (22%): Low use volume (total minutes/sessions/days), low use of key app features and less frequent use but longer sessions and greater diversity of session length
  • Samplers (31%): High use volume, broad use of key app features, frequent use, and generally short sessions
  • Light users (47%): Low to medium use volume, low use of key app features, less frequent use, and consistently short sessions

Patients in the three clusters were similar in BDD severity.

Association of Engagement Type With Treatment Response

All clusters improved significantly and similarly on the BDD-YBOCS during the treatment period (all P<0.0001):

  • Deep users: Least squares mean −13.4
  • Samplers: −10.2
  • Light users: −9.2

Symptom change did not differ between clusters, except deep users improved more than light users at a marginally significant level (P=0.054).

Implications for App Use and Development

These findings suggest clinicians need not prescribe a one-size-fits-all engagement approach with smartphone psychotherapies. This is important since individuals appear to have distinct preferences about how to engage.

However, if future research determines deep engagement is especially effective, patients should be encouraged to use apps for a minimum amount of time per session. Developers could consider strategies such as interactive content to capture attention.

In addition, patterns of engagement could be passively monitored. A drift away from patterns known to be effective could trigger coach outreach or reminders aimed at re-engaging the user (e.g., messages about the benefits of spending a few focused minutes at a time on the app).

Learn more about the Obsessive-compulsive Disorder & Related Disorders Program

Learn more about research in the Department of Psychiatry


In the largest-ever study of treatment for body dysmorphic disorder, researchers found that CBT-BDD reduced BDD symptom severity more consistently across sites.


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