Development of a short form of the compulsive internet use scale in Switzerland.

The study aims to develop a short form of the compulsive internet use scale (CIUS), which can be used in multitopic and general population health surveys and is invariant across different sexes, linguistic regions, and ages. Two general population surveys from 2013 and 2015 were used as learning (n = 1,371) and validation samples (n = 1,550), respectively. Reducing items from the original CIUS was based on the following: (a) correlated errors between items, (b) differential item functioning, and (c) measurement invariance. Methods used item response theory and latent confirmatory factor analysis for ordinal variables. The eight-item short form maintained the five dimensions of the original scale and was metric and mostly scale invariant for sex, region, and age. It fell marginally short of scale invariance (ΔCFI < 0.01) for regions in the learning sample and for sexes in the validation sample (both ΔCFI = 0.013, p < 0.01). Root mean square error of approximation was 0.045 and 0.036, and comparative fit index was 0.989 and 0.995, in the learning and validation samples, respectively, showing excellent fit of the model to data. Correlations with the full scale were r = 0.966 (learning) and r = 0.969 (validation). If the full 14-item CIUS is a valid, reliable screening instrument, then the short eight-item form is too, and can be used in multitopic, general population health surveys