Data Harmonization: Establishing Measurement Invariance across Different Assessments of the Same Construct across Adolescence.

Longitudinal measurement invariance is a major concern for developmental scholars who seek to evaluate the same underlying construct across time. Unfortunately, discontinuities in the expression of various psychological constructs, as well as essential changes in measurement that are necessitated by shifting developmental capacities and practice effects over time, make the task of establishing longitudinal invariance extremely difficult. Drawing on 5 waves of longitudinal data from 392 families (52% female; Mage_W1 = 12.89, SD = .48; Mage_W5 = 21.95, SD = .77; 199 European American and 193 Mexican American families), the current investigation sought to establish measurement invariance across developmentally appropriate changes in measures of depressive symptomatology from early adolescence through early adulthood. Using a combination of item parceling and the common and unique items from 2 assessment instruments for depressive symptoms, the data supported strong factorial invariance in youth's depressive symptoms across 5 waves of measurement. Findings suggest that traditional invariance approaches can be adapted to determine whether the same construct underlies different measurement instruments across time. This analytic strategy can allow researchers and clinicians to use more sophisticated techniques to understand changes in symptomatology regardless of changes in measurement or developmental capacity. Applying this approach to model patterns of depressive symptomatology from early adolescence to early adulthood has important clinical implications for elucidating periods when youth experience elevations in depressive symptoms and heightened needs for intervention services.