Internet Intervention for Well-being in the Context of Work-family Conflict Among Dual-earner Couples: Protocol for Four-arm Randomized Controlled Trial

Background and theoretical rationale: This study evaluates an internet-delivered psychological intervention for heterosexual dual-earner couples experiencing work-to-family conflict (WFC) and family-to-work conflict (FWC). Grounded in Greenhaus and Beutell's multidimensional framework and the Spillover-Crossover Model, the intervention targets time-based and strain-based interrole conflict. The dyadic randomized controlled design investigates individual (actor) effects and interpersonal (partner) crossover effects to test whether joint participation yields superior benefits compared to individual delivery or a waitlist control condition.

Study design and randomization: The study is a four-arm, parallel-group randomized controlled trial with the couple serving as the unit of recruitment and randomization. Couples are allocated using block randomization via the blockrand package in R with a 1.77:1.77:1 allocation ratio to one of four conditions. The conditions include a dyadic intervention, an individual female-partner intervention, an individual male-partner intervention, and a waitlist control condition.

Digital platform and delivery: The unguided 3-week intervention is hosted on Google Classroom within an institutional Google Workspace for Education environment. To ensure participant privacy, a multiple-classroom architecture assigns each individual or dyad to a private virtual classroom accessible only via individual researcher-managed credentials. Native social communication features are disabled to prevent cross-participant visibility. Built-in automated email notifications serve as digital nudges to promote task engagement.

Intervention structure: The intervention consists of two parallel strands addressing time-based and strain-based conflict. The time-based strand focuses on boundary management, segmentation and integration strategies, implementation intentions, and action planning. The strain-based strand emphasizes recognizing psychological strain transfer, self-distancing, emotional awareness, and behavioral experiments. The dyadic condition incorporates joint activities involving mutual reflection, structured dialogue, and collaborative support planning.

Statistical analysis plan: Efficacy analyses will follow the intention-to-treat principle using linear mixed-effects models to evaluate fixed effects of time, condition, and their interaction. Nested random intercepts will account for repeated observations within participants and non-independence within couples. Dyadic crossover processes will be analyzed using the Actor-Partner Interdependence Model to differentiate actor associations from partner associations. Missing data will be handled via maximum likelihood estimation within mixed-effects models or multiple imputation depending on missingness patterns.