Although ecological cognitive social capital is an important predictor of mental health, measurement remains crude. Multi-level regression with post-stratification (MRP) is a technique for computing small area estimates of survey responses, used in political science but hitherto not for estimating ecological protective factors in epidemiology.

National Survey for Wales 2016-17 data (N = 10,486) were used to produce MRP estimates of belonging and generalised trust for 410 middle super output areas covering Wales. These estimates were used to predict psychiatric admission rates in 2017 (N = 9978 cases).

Low belonging and trust are ecological risk factors for psychiatric admissions, with a 29% (25–33%) and 25% (22–29%) increase in admissions per standard deviation decrease respectively. Equivalent results for using standard simple aggregation of survey data by area suggest 8% (4–12%) and 10% (6–14%) increases in risk per standard deviation.

MRP has potential for studying ecological risk factors based on self-report measures, with greater predictive validity for incidence of psychiatric admissions than current methods.