Measurement of maternal instrumental support: findings from three population-based cohort studies.

To advance the conceptualization and measurement of mother-reported instrumental support, the degree to which an individual receives assistance in the completion of daily life tasks. The psychometric properties of a 9-item instrumental support scale were evaluated using classical (descriptive statistics, factor analyses, evaluation of construct validity) and modern (Rasch modeling, differential item functioning) methods. Differences in perceived instrumental support were evaluated as a function of mothers' socio-demographic characteristics. Factor analytic and differential item functioning analyses provided support for two components of instrumental support, household and childcare assistance. Instrumental support is distinct from structural support and the quality of mothers' social relationships. Socio-demographic characteristics (e.g., marital status, education level, income) are associated with access to instrumental support. Differentiating appropriately between support subtypes may reveal important differences in mother's qualitative instrumental support experiences and facilitate effective targeting of social support interventions.