Testing the Causal Direction of Mediation Effects in Randomized Intervention Studies

Area of Science:

• Psychology
• Statistics
• Public Health

Background:

• Prevention intervention research requires understanding causal mechanisms.
• Mediation analysis is common but has limitations in identifying causal direction.
• Cross-sectional data with randomized treatment can lead to ambiguous mediator-outcome relationships.

Purpose of the Study:

• To introduce and evaluate a novel method for empirically testing competing mediation theories.
• To address the challenge of uniquely identifying the direction of mediator-outcome relations.
• To provide tools for robust causal inference in prevention science.

Main Methods:

• Utilizing principles of direction dependence.
• Applying third higher moments (skewness, co-skewness) to identify causal direction.
• Developing significance procedures compatible with direction dependence.

Main Results:

• Third higher moments can uniquely identify the direction of mediator-outcome relations under specific conditions.
• Simulation studies demonstrate the effectiveness of the proposed tests.
• An empirical example and SPSS software implementation are provided.

Conclusions:

• Direction dependence offers a powerful approach to resolve ambiguity in mediation analysis.
• The method enhances the evaluation of causal mechanisms in prevention interventions.
• This contributes to more rigorous research on intervention effectiveness.