This study aimed to examine the factors affecting the relationship between stress and anxiety in critically ill patients. A cross-sectional research paradigm was employed to enroll patients admitted to the medical intensive care unit (ICU) of a medical university hospital. Partial least squares structural equation modeling (PLS-SEM) was used to examine the data. A total of 90 ICU patients were included in this study; 56 were men and 34 were women. The patients' mean age was 65.3 years. Only the emotional responses dimension of illness was significantly positively correlated with stress. However, the emotional responses dimension of illness representation, acute physiology and chronic health evaluation system (APACHE) score, age, and education level were significantly positively correlated with anxiety. Nevertheless, treatment control was significantly negatively correlated with anxiety. Overall, illness representations (emotional responses and treatment control), APACHE score, age, and education were important predictors of anxiety, with an explanatory power of 37.9%. We recommend that for clinically relevant practice, besides focusing on ICU patients' illness representation, attention should also be paid to their individual characteristics, such as differences in age and education levels.
