JMIR Publications

ABSTRACT

Background:

A central challenge for mental health care is making effective support scalable enough to reach the many people who lack access, without losing the human contact that keeps them engaged. Guided self-help and lay-guided online cognitive behavioral therapy (CBT) can expand access, yet most such programs still require time-consuming facilitator training, which limits how far they can scale. Existing evidence is further dominated by clinician-guided, single-cohort, CBT-only designs in clinical samples. Much less is known about peer-facilitated online group programs delivered by minimally trained lay facilitators: how much guidance such formats require, whether they transfer to non-CBT approaches, and how they affect productivity as well as symptoms, each bearing on whether effective support can be delivered at lower cost and wider reach.

Objective:

To evaluate whether The CBT Lab, a low-cost online group program using minimally trained lay peer facilitators, was associated with consistent improvements in mental health burden, positive mental health, and productivity, and to explore whether reduced guidance (CBT Mini) or different therapeutic content (IFS Peer) produced comparable outcomes and engagement.

Methods:

We conducted two complementary studies in a non-clinical sample of adults recruited from the Effective Altruism community. Study 1 was a multi-cohort observational evaluation of the standard CBT Peer format across 2023, 2024, and 2025 (N=218). Study 2 was a preference-based nonrandomized comparison of three self-selected 2024 formats: CBT Peer (n=57), CBT Mini, a reduced-guidance CBT format (n=43), and IFS Peer, a format with similar guidance to CBT Peer but with clinical content drawn from Internal Family Systems (n=37). The primary outcomes were three z-standardised composite measures, mental health burden, positive mental health and productivity, each derived from different scales.

Results:

In Study 1, CBT Peer participants showed consistent Week 0 to Week 12 improvements across cohorts in positive mental health (dRM=0.59 to 0.70), mental health burden (dRM=-0.46 to -0.53), and productivity (dRM=0.37 to 0.52). Cohort × time interactions were not statistically significant. In Study 2, baseline-adjusted Week 12 analyses and planned contrasts did not show statistically reliable format differences for mental health burden, positive mental health, or productivity. Within-format estimates suggested the most consistent Week 0 to Week 12 improvement in CBT Peer, with more selective or imprecise changes in CBT Mini and IFS Peer. On raw symptom scales, Study 1 showed PHQ-8 decreases across all cohorts (2023: 8.72 to 6.78, -1.94 points, adjusted P=.011; 2024: 9.90 to 7.31, -2.59 points, adjusted P=.002; 2025: 8.58 to 6.22, -2.36 points, adjusted P<.001), whereas GAD-7 decreases reached statistical significance only in 2025 (2023: -1.81 points, P=.062; 2024: -1.17 points, P=.077; 2025: -2.05 points, P<.001). In Study 2, baseline-adjusted Week 12 comparisons showed no reliable format differences on PHQ-8 (F(2,91)=0.83, P=.437) or GAD-7 (F(2,91)=0.79, P=.459). Session attendance was high across the three Study 1 CBT Peer cohorts (2023: M=83.2%, SD=27.6; 2024: M=80.6%, SD=23.0; 2025: M=90.0%, SD=11.7). In Study 2, attendance differed by self-selected format (F(2, 134)=20.73, P<.001), with lower attendance in CBT Mini (M=51.1%, SD=23.8) than CBT Peer (M=80.6%, SD=23.0; adjusted P<.001), whereas IFS Peer attendance (M=74.1%, SD=25.7) did not differ reliably from CBT Peer (adjusted P=.205).

Conclusions:

The CBT Peer format showed a stable observational pattern of moderate improvements in mental health burden, positive mental health, and productivity across three annual cohorts. In the preference-based comparison, adjusted analyses did not provide evidence that reduced-guidance CBT Mini or IFS Peer differed reliably from CBT Peer, although CBT Mini showed lower attendance. Because neither study included a control condition and Study 2 relied on self-selected allocation, findings should be interpreted as preliminary observational evidence rather than causal evidence of effectiveness, superiority, equivalence, or noninferiority. Clinical Trial: Study 2 was prospectively registered with ClinicalTrials.gov on 4 June 2024 (NCT06442072), prior to enrollment of the first participant. Study 1 was a non-registered observational evaluation of routine program delivery.