A structural modeling analysis of anxiety and depression in patients undergoing coronary artery bypass graft surgery

Abstract

The present study is a longitudinal study designed to explore structural relationships between anxiety, depression, personality, and background factors (e.g., gender, age, and complicated medical characteristics) in patients undergoing coronary artery bypass graft (CABG) surgery. At two timepoints before and two after CABG, 217 patients completed self-report questionnaires. To explore structural relationships, the structural equation modeling (SEM) method was applied. Using the model-generating approach, a model was developed, providing a good fit. The structural relationships revealed, in particular, the key position of neuroticism, which was related to both pre- and postoperative anxiety and depression. Relationships between anxiety and depression over time, both intra- and interrelationships, were relatively weak. Relationships between anxiety and depression at the same points in time were relatively strong, with preoperative depression leading to preoperative anxiety, and postoperative anxiety leading to postoperative depression. To provide a useful framework for development of intervention strategies, further research is needed to evaluate the plausibility of the final structural model.

Introduction

Coronary artery bypass graft surgery (CABG) is usually successful in relieving angina, but psychological adjustment to this surgical procedure is often disappointing 1, 2, 3, 4, 5.

Undergoing CABG implies a stressful experience for most patients, both before and after surgery. The stress of waiting for surgery is followed by the threat of the surgical procedure itself. Increased anxiety and depression have been reported in the preoperative period 2, 4, 6, 7. Preoperative fears mainly concern the illness itself, anesthesia, surgical procedures and thoughts relating to the period after surgery (e.g., fear of the unknown, surgical failure, death, painful wounds, and fear of loss of control) [8].

Whereas anxiety dominates prior to surgery, feelings of depression are more common in the early weeks after surgery 8, 9, 10, 11. Discomfort and weakness during early convalescence make it difficult for patients to believe that they are doing well and that surgery was successful 10, 11. Postoperative anxiety mainly involves concerns about returning to normal life and related physical activities [9]. Moreover, after release from the hospital, the patient may feel more insecure and fearful because of the absence of the support system provided by the hospital 11, 12. Finally, feelings of anxiety and depression weeks or months after surgery can be an expression of difficulties adapting to the changed postoperative and future situation, and career and family problems [8].

Several attempts have been made to study predictors of psychological outcome after cardiac surgery 2, 3, 13, 14, 15, 16, 17, 18. Prediction of psychological outcome may improve identification of patients at risk of later psychological problems. Evaluation of prospective studies shows that specific psychological outcomes are strongly predicted by their preoperative assessments, especially in the case of anxiety and depression [19]. Additionally, it is assumed that poor adjustment is more a reflection of the patient’s personality than the surgical procedure itself 3, 18. Patients with a generally fatalistic attitude seem most inclined to experience postoperative feelings of anxiety and depression [3].

Identification of determinants, leading to either good or poor psychological outcome, may have implications for the development of intervention strategies to assist those patients in need of support. In attempting to develop efficient intervention strategies, one would need to understand the underlying processes of the psychological factors involved. Examination of the structure of intrarelationships (i.e., relationships within the same variable over time) and interrelationships (i.e., relationships between different variables, both over time and at the same points in time) provide insight into how the various factors might affect one another. This structure, then, might be a useful framework for development of clinical interventions.

So far, the aim of prospective studies was to identify preoperative demographic, medical, and psychological determinants of specific psychological outcomes, without regard for the overall structure of relationships between the various variables. Therefore, the present study was designed to integrate the factors involved into one simultaneous analysis to explore the structure of intra- and interrelationships. The focus was on feelings of anxiety and depression in relation to personality and background factors (e.g., gender, age, and medical factors). Feelings of anxiety and depression were assessed prior to surgery and in the early and late postoperative period.

To explore structural relationships, structural equation modeling (SEM) has recently emerged as an accepted method [20]. SEM deals with identifying, specifying and testing models for structural relationships between substantively meaningful variables [21]. A major advantage of SEM is its ability to estimate all parameters in the model simultaneously and to provide an overall test of model fit. Moreover, SEM has the advantage of adjustment for measurement error, which requires specification of a measurement model that depicts relationships between observed variables (i.e., measured variables) and latent variables (i.e., hypothetical or theoretical constructs) [20]. Although SEM is generally used to test prespecified conceptual models, it can also be used in an exploratory manner. Using the model-generating (MG) approach 21, 22, SEM permits development of a structural model, which can be considered a first step in building a theory. Because a specific theoretical basis is lacking in this study, it was anticipated that the exploratory use of SEM would improve the understanding of psychological processes in patients undergoing CABG.

This study is a part of a longitudinal follow-up study on psychological factors in patients undergoing CABG. The aim is to enhance the understanding of psychological processes to contribute to the development of intervention strategies. Information about variations in mean level and interindividual differences has been presented in a separate study on the course of anxiety and depression [23].