Despite consistent improvement across both app conditions, the minimal between group differences found here highlight the difficulties in developing effective, scalable resources for ESWs and the limitations of unguided digital programs more broadly.
Key Findings
Results
There was no significant Time x Condition effect for primary outcome K10 psychological distress scores, with both the full app and tracking-only conditions showing similar improvements.
N = 880 ESWs were randomized to the full app (n = 440) or tracking-only (n = 440) condition.
Both conditions showed statistically significant improvements from baseline to 1-month (all ps < .001) and 3-month follow-up (all ps < .001).
The primary outcome was K10 score at 3-month post-baseline (T2).
Linear mixed model analyses were conducted based on the intention-to-treat principle.
No significant between-group difference was found despite both groups improving.
Results
App use was markedly low overall, and exploratory analyses found generally no significant differences in K10 score decreases across different levels of engagement in the full-app condition.
Engagement was examined as a moderator of outcomes in exploratory analyses.
App use was described as 'markedly low overall' across participants.
No significant differences in K10 score decreases were found across different levels of engagement in the full-app condition.
Low engagement may have limited the ability to detect intervention effects.
Results
At higher baseline psychological distress levels, participants in the full-app condition showed a significant decrease in PTSD symptoms from baseline to 1-month, whereas the tracking-only group did not.
This finding emerged from exploratory moderation analyses examining baseline severity as a moderator.
The effect was statistically significant (p = .002) with a large effect size (d = -1.43).
This differential effect was observed at 1-month follow-up (T1) but the pattern for 3-month follow-up was not specifically highlighted.
This suggests the full app may offer added benefit for more severely distressed ESWs, particularly for PTSD symptom reduction.
Methods
The study recruited emergency service workers with elevated psychological distress, defined as a Kessler Psychological Distress Scale (K10) score greater than 15.
Eligibility required K10 > 15, indicating at least mild to moderate psychological distress.
ESWs are described as routinely exposed to highly stressful and potentially traumatic events, leading to high rates of psychological distress.
The study was registered with the Australian New Zealand Clinical Trials Registry (ACTRN12622001324707).
Assessments occurred at baseline (T0), 1-month (T1), and 3-month (T2) post-baseline via online self-report questionnaires.
Methods
The Build Back Better app intervention included mindfulness, behavioural activation, trauma-focused cognitive therapy skills, activity and mood monitoring, and healthy coping strategies.
The control condition was a mood/activity tracking-only version of the same app.
The active intervention was described as the 'full version' of the Build Back Better app.
The app was unguided (no therapist or coach involvement).
The design aimed to overcome barriers to help-seeking common in emergency service worker populations.
Discussion
The authors concluded that the findings highlight the difficulties in developing effective, scalable resources for emergency service workers and the limitations of unguided digital programs more broadly.
Both conditions improved, but the lack of differential improvement between active and control conditions limits conclusions about the active components of the app.
The authors note this reflects broader challenges with unguided digital mental health interventions.
Low overall app engagement was identified as a key contextual factor.
Early intervention via digital tools was described as vital to prevent chronic impairment and psychiatric disorders in this population.
What This Means
This research suggests that a smartphone app called 'Build Back Better,' designed specifically for emergency service workers (such as paramedics, firefighters, and police officers) experiencing psychological distress, did not outperform a simpler mood and activity tracking-only version of the same app. In a large trial of 880 workers, both groups improved significantly in psychological distress over three months, but the improvements were nearly identical between those using the full therapeutic app and those using only the basic tracking tool. This makes it difficult to attribute the improvements to the specific therapeutic content (mindfulness, trauma-focused skills, etc.) rather than simply to the act of monitoring one's mood and activity.
One notable exception was found in exploratory analyses: among workers with higher levels of distress at the start of the study, those using the full app showed a large and significant reduction in post-traumatic stress disorder (PTSD) symptoms at one month (effect size d = -1.43), while the tracking-only group did not. This suggests the full app's therapeutic content might be particularly beneficial for more severely affected workers, though this finding was exploratory and should be interpreted cautiously. Overall engagement with the app was also reported as markedly low, which may have limited the ability to detect broader benefits of the full intervention.
This research suggests that while digital mental health tools hold promise for reaching emergency service workers who may face barriers to seeking traditional help, simply providing a comprehensive app is not sufficient on its own. The findings point to the broader challenge of making unguided digital programs effective in real-world settings, where users often do not engage with apps as intended. Future efforts may need to incorporate guided support, better engagement strategies, or more targeted approaches for workers with higher levels of distress.
Deady M, Gregory M, Wong Q, Meuldijk D, Collins D, Sander L, et al.. (2026). Efficacy of a smartphone app to improve mental health among emergency service workers: A randomised controlled trial.. PloS one. https://doi.org/10.1371/journal.pone.0342419