Indigenous Polygynous Household Structure and Adolescent Internalizing Symptoms in Senegalese Wolof Families: A Sibling-Fixed-Effects Estimation of Co-Wife Status and Differential Investment

The study exploits sibling fixed-effects estimation to control for unobserved household-level confounders, comparing adolescents raised in the same household but occupying different positions in the co-wife hierarchy. Using a theoretical framework that integrates life-history theory with indigenous Wolof kinship concepts, the analysis specifies a sibling fixed-effects model that would permit estimation of the association between maternal co-wife rank and adolescent internalizing symptoms, net of shared household characteristics. The analysis does not report empirical estimates; rather, it develops the identification strategy, specifies the data requirements, and derives the boundary conditions under which sibling fixed-effects estimation can credibly identify differential investment effects. Co-wife status is a theoretically distinct dimension of household stratification that cannot be reduced to household-level polygyny, and that sibling fixed-effects designs offer a credible strategy for isolating its effects on adolescent mental health.