Abstract
<p>Psychological stress is central to health and diseases. Yet heterogeneous definitions and insufficient theoretical integration lead to findings that are difficult to replicate or compare, ultimately hindering their translation into practice. To address this problem, we aimed to identify the fundamental and conceptually distinct components of psychological stress and integrate them into a unified definition and model. We systematically reviewed 67 existing definitions of psychological stress from previous publications and identified their core components. We quantified both the use frequency of each component and patterns of co-occurrence across the literature. We also reviewed major theoretical models to evaluate how comprehensively each model captured those core stress-related components. Existing definitions and theories were found to capture only partial aspects of the stress process, resulting in a fragmented conceptualization. To reconcile these fragmented perspectives and establish a cohesive foundation, we synthesize these core components into a novel framework. We redefine psychological stress as a perceived imbalance between stressors and available resources, with stressors arising from internal needs or external demands and corresponding internal and external resources. Cognitive appraisal is central to the stress process. Notably, internal needs represent an important class of stressors, yet they have received less attention than external demands in the past. To situate this definition within the broader stress process, we propose a Cognitive Integration Model (CIM). The CIM specifies how stressors and resources are dynamically integrated through cognition to generate psychological stress, whereas coping and responses are positioned as downstream components that provide feedback regulation and link stress to health outcomes. These components across the entire stress process may be jointly shaped by genetic and environmental factors. Together, this unified definition and model provide a common framework for integrating stress research across diverse theories, terminologies, and methods. This framework reframes psychological stress not as a purely environmental exposure, but as a product of gene–environment interaction.</p>