# Longitudinal Associations Between Materialism and Problematic Smartphone Use in Adolescence: Within- and Between-Person Effects

## TL;DR

This study explores how materialism and problematic smartphone use in adolescents influence each other over time.

## Contribution

The study introduces a novel longitudinal analysis of within- and between-person effects linking materialism and problematic smartphone use.

## Key findings

- Problematic smartphone use and materialism show reciprocal associations at the between-person level over time.
- No significant within-person level associations were found between problematic smartphone use and materialism.
- Disaggregating within- and between-person effects is crucial for understanding longitudinal associations.

## Abstract

Although there are theoretically expected associations between problematic smartphone use (PSU) and materialism, there is a lack of research that examines these associations using a longitudinal design, focusing on both within-person and between-person effects. Clarifying this relationship may inform interventions for these related conditions. Accordingly, data from three annual waves collected from a substantial group of Chinese adolescents (N = 3029, Mage = 12.26 ± 2.36, male: 50.00%) were used to assess within-person and between-person effects in the association between PSU and materialism. Traditional cross-lagged panel models were utilized to analyze the data, which consistently showed reciprocal positive associations between PSU and materialism across all waves. In contrast, the random intercept cross-lagged panel model revealed that PSU and materialism exhibited reciprocal associations over time at the between-person level. However, no significant cross-lagged linkage was observed between PSU and materialism at the within-person level. These findings enhance our understanding of the temporal dynamic relationship between PSU and materialism and underscore the necessity to disaggregate within-person and between-person effects to elucidate the nature of the longitudinal associations between PSU and materialism. The study also has implications for theoretical and practical understanding.