Psychiatric Bed Registry Accuracy and Trauma-Related Mental Health Readmission in Nigerian General Hospitals: An Instrumental-Variable Analysis of Referral Catchment Boundaries

Psychiatric bed registries in Nigerian general hospitals are intended to guide referral decisions for trauma-exposed patients requiring inpatient mental health care, yet the accuracy of these registries varies systematically with hospital catchment characteristics. Using a theoretical instrumental-variable framework applied to the structure of Nigerian general hospital referral networks, the analysis specifies conditions under which catchment-boundary variation provides exogenous variation in measured bed supply. Registry inaccuracy is not classical measurement error but a structured phenomenon correlated with catchment size and trauma caseload, and that instrumental-variable strategies exploiting referral boundaries can recover consistent estimates of the bed-supply effect on readmission where ordinary least squares cannot. The contribution is a formal characterisation of the identification problem and a set of testable propositions linking registry accuracy, catchment geography, and readmission risk. The analysis implies that readmission studies using uncorrected registry data will understate the protective effect of bed availability for trauma-exposed patients, and that catchment-boundary instruments offer a feasible identification strategy in settings where administrative data are imperfect.