Theory of Planned Behavior in Explaining Media Effects on Health-related Outcomes : A Systematic Review

Goal: Social scientists regard health behaviors as an outcome of rational communication processes (Armitage & Conner, 2001). The theory of planned behavior (i.e., TPB, Ajzen, 1991) has been applied to explain individuals’ various behavioral outcomes to comply with many different health-related messages and communication (e.g., physical activity, Gray & Harrington, 2011). This systematic review aims to analyze the adoption of the theory of planned behavior in
examining media effects on individuals’ health-related outcomes in the recent decade. It will provide the pattern of media effects on health behaviors among individuals, with which researchers could easily address the highlights in previous studies and benefit them in future studies.
Method: Based on the searching queries that constrained the sample with the SSCI journals in English, time period (i.e., 2010-01-01—2021-10-31) and involving the TPB and media (i.e., information/media/message/exposure/coverage), 156 articles were found. After checking titles and abstracts, 91 articles were excluded since they did not concern a health-related outcome. Further, full texts were screened with 32 articles remaining in the final sample. The recall rate of this study is 42%, and the precision rate is 49%. As for coding scheme, the current study involved coding for the basic characteristics (i.e., study year, study area, sample size, etc.) as well as coding criteria about the TPB and the outcomes (i.e., dependent variables, media type, characteristics of the TPB variables, etc.). After the pretest, two more coding criteria were involved in the scheme (i.e., the extension of the model, inclusion of other types of norms).
Findings: Descriptive pattern: The current study revealed that the theory of planned behavior was frequently adopted in explaining health-related outcomes in the recent decade. An increase appeared during 2015-2018, and it experienced a slight drop in the recent three years. The TPB was able to explain various health behaviors from disease prevention to healthy lifestyles that may benefit the well-being of society.Qualitative evaluation: This review found that the validity of studies that examined the media effects on individuals’ behaviors with the TPB was somehow weakened due to their limited study contexts. Causality among variables was hard to test due to their data collection method and study design. However, the external validity was raised owing to the large sample size and representative sample characteristics in previous studies. The reliability of studies examining media effects on individuals’ behaviors with the TPB was comparatively high in the recent decade. Consistent with previous reviews, attitudes toward the behavior presented to be the most powerful predictor, followed by PBC. Also, media, together with the TPB variables, accounted for around 50% of the variance of individuals’ behavioral intention to health outcomes. Conclusions: Most of the studies in the recent decade provided empirical contribution—new empirical evidence, by examining the theory with a different method and in different contexts. Some of them provided conceptual contribution—revising existing relationships by adding mediators/moderators or specifying the independent variables. There were still questions remained unsolved from the previous studies but worth attention.