Community-Based Trauma Rehabilitation Group Size and Mental Health Relapse in Post-Conflict Rwanda: A Multilevel Analysis of Group Composition Threshold Effects

Community-based trauma rehabilitation in post-conflict settings is often organised around small groups, yet the optimal group size for sustaining mental health gains remains unspecified. The model treats group size as a compositional parameter that governs the balance between social support and exposure to collective distress, generating a predicted threshold beyond which marginal increases in group size raise rather than lower relapse risk. Because no primary cohort data were available for estimation, the paper formalises the mechanism, derives testable propositions, and specifies the multilevel design required to identify threshold effects. It further reports the distribution of a related community-level indicator—family planning messages at community meetings—across fifteen African country surveys (N = 15, mean = 29.733, SD = 17.495), which illustrates the between-country heterogeneity that any community-based programme must accommodate. The contribution is a specification of group size as a modifiable programme parameter with non-monotonic consequences, together with the identification strategy needed to test it.