Indigenous Age-Set Cohort Exposure and Men's Mental Health Help-Seeking in Kenyan Maasai Communities: A Regression-Discontinuity Estimation of Normative Masculinity Windows

Maasai age-set cohorts create sharp, calendar-defined transitions in normative masculinity, yet the causal effect of cohort exposure on men's mental health help-seeking has not been identified. The analysis is a design and power evaluation, not an empirical estimate: no observational data are used or claimed. Using a before-after-control-impact estimator with between-cluster SD = 6.0, residual SD = 4.5, and intraclass correlation = 0.64, power was estimated across 2000 design cells for cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points. The design requires 54 clusters to detect a 5-percentage-point effect at 80% power. Minimum detectable effects at 80% power are reported for each cluster count, and the implications for the feasibility of cohort-based mental health research in Maasai communities are discussed. The normative window created by age-set promotion is a defensible identification strategy, but that its statistical demands exceed what most single-community studies can supply.